Invasive Aspergillosis

1. Clinical Overview

Summary

Invasive Aspergillosis (IA) is a life-threatening opportunistic fungal infection caused predominantly by Aspergillus fumigatus (90% of cases), with less common species including A. flavus, A. niger, and A. terreus. [1] It represents one of the most serious infectious complications in profoundly immunocompromised patients, particularly those with prolonged neutropenia (absolute neutrophil count less than 0.5 × 10⁹/L for >10 days), haematopoietic stem cell transplant (HSCT) recipients, and patients receiving intensive immunosuppressive therapy. [2]

The pathogen is a ubiquitous environmental mould found in soil, decaying vegetation, and air. Healthy individuals inhale hundreds of Aspergillus conidia (spores) daily without consequence due to intact innate immunity. However, in vulnerable hosts with impaired cellular immunity or phagocytic dysfunction, these inhaled spores germinate into invasive hyphae that demonstrate a characteristic propensity for angioinvasion—penetrating blood vessel walls and causing thrombosis, haemorrhagic infarction, and tissue necrosis. [3]

Despite advances in antifungal therapy and supportive care, invasive aspergillosis remains associated with mortality rates of 30-50% in haematology patients, exceeding 90% in those with central nervous system involvement or refractory disease. [4] Early recognition, prompt initiation of appropriate antifungal therapy, and immune reconstitution are critical determinants of survival. The disease exemplifies the intersection of mycology, immunology, and critical care medicine, making it essential knowledge for physicians managing immunocompromised populations.

Key Facts

The Aspergillus Disease Spectrum:

Understanding the diverse clinical manifestations of Aspergillus is crucial for differential diagnosis:

1. Aspergilloma (Fungal Ball): Colonisation of pre-existing lung cavity (e.g., post-TB, sarcoidosis) without tissue invasion. Presents with haemoptysis. Non-invasive. [5]

2. Allergic Bronchopulmonary Aspergillosis (ABPA): Type I and III hypersensitivity reaction in asthma/cystic fibrosis patients. Characterised by eosinophilia, elevated IgE, central bronchiectasis. [6]

3. Chronic Pulmonary Aspergillosis (CPA): Slow progressive infection over ≥3 months in patients with underlying lung disease and mild immunosuppression. Cavitation and fibrosis. [7]

4. Invasive Aspergillosis: Acute, aggressive tissue invasion in profoundly immunocompromised hosts. The focus of this topic. [1]

Galactomannan Detection:

Galactomannan is a polysaccharide component of the Aspergillus cell wall that is released into blood and body fluids during active fungal growth. [8] Key characteristics:

• Optical density index (ODI): Serum ≥0.5 on two consecutive samples, or single BAL fluid ≥1.0 considered positive
• Lead time: Often detectable 5-8 days before clinical symptoms or radiological changes
• Sensitivity: 60-70% in serum (higher in BAL fluid 80-90%)
• False positives: Piperacillin-tazobactam, amoxicillin-clavulanate, certain dietary sources
• False negatives: Anti-mould prophylaxis (posaconazole, voriconazole) reduces sensitivity [9]

Voriconazole—The Gold Standard:

Voriconazole established superiority over amphotericin B deoxycholate in the landmark Herbrecht trial (2002), demonstrating improved survival (71% vs 58%) and fewer severe adverse effects. [10] Critical pharmacological considerations:

• Loading required: Due to non-linear pharmacokinetics (enzyme saturation)
• Therapeutic drug monitoring: Target trough 1-5.5 mg/L (2-6 mg/L in CNS disease)
• CYP2C19 polymorphisms: Genetic variability causes wide inter-individual variation
• Unique toxicities: Reversible visual disturbances (30%), photosensitivity, hepatotoxicity, QTc prolongation, periostitis with long-term use [11]

Clinical Pearls

The "Halo Sign": A pulmonary nodule or mass surrounded by ground-glass opacity on CT chest represents the hallmark early radiological finding. The central nodule consists of fungal invasion with associated infarction, while the surrounding "halo" represents haemorrhage from angioinvasion. This sign is transient, typically visible only in the first 3-7 days, and has 61% sensitivity and 77% specificity for IA in haematology patients. [12] While classic, it is not pathognomonic—differential includes haemorrhagic metastases, Wegener's granulomatosis, and viral pneumonia.

The "Air Crescent Sign": A crescent of air appearing within or surrounding a pulmonary nodule or mass represents a later finding (typically 2-3 weeks after symptom onset), indicating neutrophil recovery and immune-mediated clearance of necrotic tissue. This paradoxical radiological progression during clinical improvement reflects successful host response and is associated with better prognosis. [13] However, it also signals increased risk of massive haemoptysis as cavitation exposes eroded vessels.

The "Empiric Therapy" Principle: In a neutropenic patient with persistent or recurrent fever despite 4-7 days of appropriate broad-spectrum antibacterial therapy, empiric anti-mould therapy should be initiated even without definitive microbiological or radiological evidence. This pre-emptive approach is supported by IDSA guidelines and reflects the high mortality of delayed treatment in this population. [1] Risk stratification using galactomannan surveillance and CT imaging guides this decision.

The "Aspergillus Triad": Neutropenia + Refractory Fever + Pulmonary Nodules = Invasive Aspergillosis until proven otherwise. This clinical constellation demands urgent action.

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2. Epidemiology

Incidence and Prevalence

Invasive aspergillosis occurs almost exclusively in immunocompromised populations, with incidence varying by underlying condition and degree of immunosuppression:

The incidence has increased over recent decades due to:

1. More intensive chemotherapy regimens
2. Expanded use of haematopoietic stem cell transplantation
3. Increased numbers of solid organ transplants
4. Prolonged survival of immunocompromised patients
5. Wider use of immunosuppressive agents (biologics, corticosteroids) [2]

Paradoxically, the introduction of anti-mould prophylaxis (posaconazole, voriconazole) in high-risk populations has reduced incidence but increased the proportion of breakthrough infections with non-fumigatus and potentially resistant species. [20]

Demographics

Age: Reflects underlying conditions—bimodal distribution with paediatric peak (primary immunodeficiencies, childhood leukaemia) and adult peak (haematological malignancies, transplantation). Median age 45-65 years in haematology populations. [21]

Sex: Male predominance (60-65%) likely reflects higher incidence of haematological malignancies and smoking-related lung disease in males. [21]

Geography: Ubiquitous worldwide distribution. A. fumigatus predominates globally, but regional variations exist (A. flavus more common in Middle East, A. lentulus emerging in Europe). [22]

Seasonality: Some data suggest higher incidence in late summer/autumn, potentially related to agricultural activity and spore dispersal, but nosocomial acquisition from hospital construction/renovation is increasingly recognised. [23]

Major Risk Factors

1. Prolonged Neutropenia (Highest Risk)

• Definition: Absolute neutrophil count (ANC) less than 0.5 × 10⁹/L for >10 days
• Risk increases with duration: 10% at 10 days, 25% at 20 days, >40% at 30 days without prophylaxis [14]
• Populations: AML/MDS induction chemotherapy, relapsed/refractory leukaemia, aplastic anaemia

2. Haematopoietic Stem Cell Transplantation

• Allogeneic HSCT: Risk periods include neutropenic phase (0-30 days), acute GVHD treatment (30-100 days), and chronic GVHD (>100 days) [15]
• Cord blood transplants: Higher risk due to delayed engraftment
• HLA-mismatched/haploidentical transplants: Increased immunosuppression
• T-cell depletion: Impaired cellular immunity

3. Corticosteroid Therapy

• Dose-dependent risk: Prednisone >0.3 mg/kg/day (or equivalent) for >3 weeks [24]
• Mechanism: Impairs alveolar macrophage function, neutrophil chemotaxis, and cell-mediated immunity
• Populations: GVHD treatment, autoimmune conditions, asthma/COPD exacerbations

4. Solid Organ Transplantation

• Lung transplant: Highest risk (3-15%) due to direct environmental exposure and anastomotic ischaemia [16]
• Liver transplant: Risk factors include prolonged surgery, re-transplantation, renal replacement therapy
• Heart/kidney transplant: Lower baseline risk, increases with rejection episodes

5. Inherited Immunodeficiencies

• Chronic granulomatous disease (CGD): Defective NADPH oxidase → impaired neutrophil killing. Lifetime IA risk 25-40%. [18]
• Severe combined immunodeficiency (SCID): T and B cell defects
• CARD9 deficiency: Impaired anti-fungal immunity
• Hyper-IgE syndrome (Job syndrome): Defective Th17 responses

6. Emerging Risk Factors

• Targeted therapies: Ibrutinib (BTK inhibitor), alemtuzumab (anti-CD52), CAR T-cell therapy [25]
• COVID-19: Severe disease with corticosteroids ± IL-6 inhibitors → COVID-associated pulmonary aspergillosis (CAPA) [19]
• Cirrhosis: Advanced liver disease with immune dysfunction
• Critical illness: Prolonged ICU stay, mechanical ventilation, broad-spectrum antibiotics

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3. Aetiology & Pathophysiology

Causative Organisms

Aspergillus species are saprophytic moulds ubiquitous in the environment, particularly soil, decaying organic matter, and air. Over 250 species exist, but human infection is dominated by:

Cryptic species (A. lentulus, A. udagawae) are increasingly recognised, often with reduced azole susceptibility. [22]

Molecular Pathogenesis

Phase 1: Inhalation and Deposition

Humans inhale 100-1000 Aspergillus conidia daily. [3] These small spores (2-3 μm for A. fumigatus) bypass upper airway defences and deposit in terminal airways and alveoli.

Phase 2: Immune Evasion

In immunocompetent hosts:

• Alveolar macrophages rapidly phagocytose and kill conidia via reactive oxygen species (ROS)
• Neutrophils are recruited if spores germinate, releasing neutrophil extracellular traps (NETs) and toxic granules
• Dendritic cells present antigens and activate T-cell responses (Th1, Th17) [26]

In immunocompromised hosts, this defence cascade fails:

• Neutropenia: Absent oxidative killing and NET formation
• Corticosteroids: Impaired macrophage activation, reduced cytokine production
• Calcineurin inhibitors: Suppressed T-cell responses
• CGD: Defective NADPH oxidase → no ROS production [18]

Phase 3: Germination and Hyphal Formation

Unopposed by immunity, conidia swell and germinate into invasive hyphae within 6-12 hours. Hyphae possess:

• Adhesins: Bind to extracellular matrix proteins (laminin, fibrinogen, complement)
• Proteases: Degrade basement membrane and elastin
• Toxins: Gliotoxin (immunosuppressive), restrictocin (ribotoxin) [27]

Phase 4: Angioinvasion

The pathognomonic feature of invasive aspergillosis is vascular invasion. Hyphae demonstrate tropism for blood vessels:

1. Endothelial adhesion: via platelet receptors and complement
2. Vessel wall penetration: protease-mediated degradation
3. Thrombosis: platelet activation and coagulation cascade
4. Haemorrhagic infarction: tissue hypoxia and necrosis
5. Haemorrhage: vessel erosion → haemoptysis [3]

This angioinvasive phenotype distinguishes IA from other pneumonias and explains classic radiological signs (halo sign = haemorrhage; air crescent = infarct cavitation).

Phase 5: Dissemination

Haematogenous spread occurs in 10-30% of cases, with predilection for: [28]

• Brain: Multiple abscesses, often at grey-white matter junction
• Heart: Myocarditis, endocarditis (particularly prosthetic valves)
• Kidneys: Cortical abscesses
• Liver and spleen: Microabscesses
• Skin: Erythematous to necrotic papules/nodules

Host Factors in Pathogenesis

Critical Immune Cells:

• Neutrophils: Primary defence. NADPH oxidase-mediated killing. Absent in neutropenia/CGD.
• Alveolar macrophages: First responders. Phagocytose conidia. Impaired by corticosteroids.
• Dendritic cells: Antigen presentation. Th1/Th17 priming. Suppressed by calcineurin inhibitors.
• NK cells: IFN-γ production. Direct cytotoxicity. [26]

Cytokine Networks:

• Pro-inflammatory: TNF-α, IL-1β, IL-6 (recruit and activate phagocytes)
• Th1: IFN-γ (macrophage activation)
• Th17: IL-17, IL-22 (neutrophil recruitment, epithelial defence)
• Regulatory: IL-10, TGF-β (balance inflammation, but may impair fungal clearance) [26]

Exam Detail: Advanced Pathophysiology: Genetic Susceptibility

Emerging evidence suggests genetic variation influences susceptibility beyond classic immunodeficiencies:

1. Dectin-1 (CLEC7A) polymorphisms: β-glucan receptor on phagocytes. Y238X variant associated with increased IA risk in HSCT. [29]

2. Pentraxin-3 (PTX3) deficiency: Opsonin recognising galactomannan. Polymorphisms correlate with post-HSCT IA. [30]

3. Toll-like receptor polymorphisms: TLR4 variants alter Aspergillus recognition and cytokine responses.

4. Plasminogen gene variants: Affect fibrinolysis and hyphal penetration of thrombi.

These pharmacogenomic insights may enable future risk stratification and personalised prophylaxis strategies.

Azole Resistance Mechanisms:

Environmental azole use (agriculture) has driven selection of A. fumigatus cyp51A mutations (TR34/L98H, TR46/Y121F/T289A), causing pan-azole resistance. [31] Prevalence varies geographically (>20% in Netherlands, less than 5% in most regions). Clinical resistance may also emerge during prolonged therapy via efflux pump upregulation or target gene modification. Always send isolates for susceptibility testing.

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4. Clinical Presentation

Pulmonary Invasive Aspergillosis (85-90% of Cases)

Cardinal Symptoms:

1. Fever: Persistent or recurrent despite ≥96 hours of broad-spectrum antibacterial therapy. Present in 90% but may be absent in patients on corticosteroids. [1]

2. Pleuritic chest pain: Sharp, localised pain exacerbated by breathing/coughing. Indicates pleural involvement from peripheral infarction. Present in 30-40%. [32]

3. Cough: Initially dry and non-productive, may become productive as cavitation develops. Present in 60-70%.

4. Haemoptysis: Ranges from blood-streaked sputum to life-threatening massive haemoptysis (>200 mL/24h). Indicates vascular erosion. Occurs in 15-30%, more common with cavitation/air crescent sign. [33]

5. Dyspnoea: Progressive breathlessness reflecting extent of pulmonary involvement and respiratory failure.

Associated Features:

• Constitutional symptoms: Fatigue, malaise, weight loss (particularly in chronic/progressive disease)
• Hypoxia: Oxygen desaturation, increased supplementary oxygen requirements
• Respiratory failure: May progress rapidly in neutropenic patients

Atypical Presentations:

• Minimal symptoms: Profoundly neutropenic patients may present with isolated fever and subtle radiological changes
• Corticosteroid masking: High-dose steroids suppress inflammatory response, delaying symptom onset
• Tracheobronchitis: Ulcerative airway disease without parenchymal invasion (seen in lung transplant, AIDS) [34]

Extra-Pulmonary Invasive Aspergillosis

1. Central Nervous System (CNS) Aspergillosis (5-10%)

The second most common site, associated with >90% mortality despite therapy. [35]

Presentations:

• Brain abscess: Focal neurological deficits (hemiparesis, aphasia, cranial nerve palsies)
• Seizures: Focal or generalised
• Altered consciousness: Confusion, decreased GCS
• Raised intracranial pressure: Headache, vomiting, papilloedema
• Meningitis: Rare, associated with neurosurgical procedures

Pathogenesis: Haematogenous dissemination (70%) or direct extension from sinuses (30%). Multiple lesions at grey-white matter junction characteristic. Haemorrhagic infarction common.

2. Invasive Aspergillus Sinusitis

Acute invasive rhinosinusitis:

• Symptoms: Nasal congestion, facial pain, epistaxis, fever
• Classic sign: Black necrotic eschar on nasal mucosa or hard palate (tissue infarction)
• Complications: Orbital invasion (proptosis, ophthalmoplegia, vision loss), cavernous sinus thrombosis, intracranial extension

Requires urgent ENT assessment and surgical debridement. [36]

3. Cutaneous Aspergillosis

Primary (rare, traumatic inoculation at catheter sites, burns):

• Erythematous macule → violaceous papule → black necrotic eschar

Secondary (disseminated):

• Multiple skin nodules, mimicking bacterial sepsis or vasculitis [37]

4. Cardiac Aspergillosis

• Endocarditis: Prosthetic valves, post-cardiac surgery. Large vegetations, embolic phenomena
• Myocarditis: Myocardial abscesses, arrhythmias
• Pericarditis: Rare, post-cardiac surgery [28]

5. Other Sites

• Gastrointestinal: Rare. Ulcers, perforation, bleeding
• Hepatosplenic: Microabscesses in prolonged neutropenia (may become apparent during immune reconstitution)
• Renal: Cortical infarcts, abscesses
• Osteomyelitis: Vertebral (post-surgery), ribs (contiguous spread)

Clinical Syndromes by Host

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5. Clinical Examination

General Inspection

In the immunocompromised patient with suspected invasive aspergillosis, systematic examination should focus on:

Vital Signs:

• Fever: Often >38.5°C, may be continuous or intermittent. Absence does not exclude infection, particularly in steroid-treated patients
• Tachypnoea: Respiratory rate >20-24/min suggests pulmonary involvement or sepsis
• Hypoxia: SpO₂ less than 92% on room air warrants urgent assessment
• Haemodynamic instability: Tachycardia, hypotension indicate sepsis/dissemination

Systemic Assessment:

• Cachexia: Weight loss and muscle wasting in prolonged infection
• Pallor: Anaemia from underlying haematological disease or bone marrow suppression
• Jaundice: Hepatic involvement (rare) or voriconazole hepatotoxicity

Respiratory Examination

Inspection:

• Work of breathing: Use of accessory muscles, intercostal recession
• Chest wall: Surgical scars (thoracotomy, transplant), central venous access devices

Palpation:

• Tracheal deviation: Suggests large effusion, pneumothorax, or mass effect (rare)
• Expansion: May be reduced on affected side if large consolidation/effusion

Percussion:

• Usually resonant (aspergillosis causes consolidation, not effusion typically)
• Dullness suggests secondary pleural effusion or extensive consolidation

Auscultation:

• Often surprisingly normal: Especially in early disease or profound neutropenia (absent inflammatory response → minimal auscultatory signs)
• Crackles: Fine inspiratory crackles if secondary alveolar involvement
• Pleural rub: Suggests infarction with pleural irritation (associated with pleuritic pain)
• Reduced breath sounds: Over areas of consolidation or large cavities

Head and Neck Examination

Critical in immunocompromised patients with fever:

Nasal/Sinus Examination:

• Black necrotic eschar: On nasal mucosa, turbinates, or hard palate is PATHOGNOMONIC for invasive fungal sinusitis (aspergillosis or mucormycosis). Requires urgent ENT/surgical intervention. [36]
• Epistaxis, nasal congestion, facial pain: Less specific but concerning in context

Oral Examination:

• Palatal necrosis: Black eschar on hard palate from sinus extension
• Oral ulceration: Consider other infections (HSV, candidiasis) or mucositis

Eye Examination:

• Proptosis: Orbital invasion from sinus extension
• Ophthalmoplegia: CN III, IV, VI palsies suggest cavernous sinus involvement
• Visual field defects: CNS involvement
• Fundoscopy: Endophthalmitis (rare) shows vitreous opacities, retinal infiltrates

Neurological Examination

Essential if ANY neurological symptoms or disseminated disease:

Mental Status:

• Confusion, drowsiness: Raised ICP or meningoencephalitis
• GCS: Quantify level of consciousness

Cranial Nerves:

• CN palsies: Suggest skull base involvement or brain abscess

Motor/Sensory:

• Focal weakness: Hemiparesis indicates brain abscess (commonly frontal/parietal)
• Sensory loss: Hemisensory loss with abscess

Cerebellar:

• Ataxia, dysmetria: Posterior fossa involvement

Meningism:

• Neck stiffness: Rare (meningitis uncommon), more often abscess/cerebritis

Cardiovascular Examination

• New murmur: Consider endocarditis (particularly post-cardiac surgery, prosthetic valves)
• Signs of embolic phenomena: Splinter haemorrhages, Janeway lesions (rare in fungal endocarditis)

Skin Examination

Disseminated disease marker:

• Erythematous macules → violaceous papules → black necrotic eschars: Evolution of cutaneous lesions
• Distribution: Any site, often trunk/extremities
• Morphology: Central necrosis with surrounding erythema mimics ecthyma gangrenosum (Pseudomonas) or purpura fulminans [37]

Abdominal Examination

• Usually unremarkable
• Hepatosplenomegaly: May indicate hepatosplenic candidiasis (different pathogen) or underlying haematological disease
• Tenderness: Rare GI involvement may cause localised pain

Key Examination Pearls

The "Silent Chest in Neutropenia": Profoundly neutropenic patients (less than 0.1 × 10⁹/L) may have extensive pulmonary aspergillosis on imaging yet completely normal auscultation. The inflammatory response that generates crackles and consolidation requires neutrophils. Always obtain imaging regardless of benign examination.

The "Black Eschar Sign": Any necrotic black tissue in the nasal passages, sinuses, or palate in an immunocompromised patient is invasive fungal infection until proven otherwise. This requires URGENT surgical debridement and antifungal therapy—delay significantly increases mortality.

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6. Differential Diagnosis

Invasive aspergillosis must be distinguished from other pulmonary infections and non-infectious processes in immunocompromised hosts:

Infectious Differentials

Non-Infectious Differentials

Practical Differentiation Strategy

Step 1: Microbiology

• BAL: Send for bacterial culture, AFB, fungal culture, galactomannan, β-D-glucan, PCP immunofluorescence, viral PCR (CMV, HSV, adenovirus)
• Serum: Galactomannan, β-D-glucan, Aspergillus PCR

Step 2: Radiology

• Nodules with halo sign: Aspergillus (also consider mucormycosis, candidiasis, haemorrhagic metastases)
• Diffuse ground-glass: PCP, viral, oedema, haemorrhage
• Cavitation: TB, Nocardia, aspergillosis (later stage)
• Tree-in-bud: Bacterial bronchopneumonia, atypical mycobacteria

Step 3: Clinical Context

• Neutropenia: Aspergillus, bacterial, Candida
• CD4 less than 200: PCP, CMV, disseminated fungi (Cryptococcus, Histoplasma)
• Post-transplant: CMV (early), aspergillus, community-acquired respiratory viruses
• High-dose steroids: Aspergillus, PCP, Nocardia, Strongyloides

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7. Investigations

Imaging

High-Resolution CT Chest (HRCT): Gold Standard

CT is far superior to chest X-ray (sensitivity 50% vs 100%) and should be performed urgently in all suspected cases. [12,38]

Classic CT Findings:

Chest X-Ray:

• Often normal in early disease, particularly in neutropenia
• May show non-specific infiltrates, nodules, or cavitation later
• Not adequate to exclude invasive aspergillosis—proceed to HRCT if clinical suspicion

Other Imaging:

• CT Brain (with contrast): If neurological symptoms or CNS signs. Shows multiple ring-enhancing abscesses, often at grey-white junction, with surrounding oedema. [35]
• CT Sinuses: If sinus symptoms. Shows mucosal thickening, bony erosion, soft tissue invasion.
• MRI Brain: Superior to CT for posterior fossa, skull base extension. T2 hypointense rim characteristic.
• PET-CT: May help differentiate active infection from post-treatment scarring, but not routine. [39]

Microbiological Investigations

1. Galactomannan Antigen (GM)

A cell wall polysaccharide released during fungal growth. [8,9]

Serum GM:

• Threshold: Optical density index (ODI) ≥0.5 on two consecutive samples
• Sensitivity: 60-70% (higher in prolonged neutropenia, lower with azole prophylaxis)
• Specificity: 85-90%
• False positives: Piperacillin-tazobactam, amoxicillin-clavulanate, certain infant formulas, cross-reactivity with other fungi
• False negatives: Anti-mould prophylaxis (voriconazole, posaconazole), early disease, localised infection
• Kinetics: Serial monitoring (twice weekly in high-risk neutropenia) improves sensitivity. Rising titres suggest active disease.

Bronchoalveolar Lavage (BAL) GM:

• Threshold: ODI ≥1.0 (single sample)
• Sensitivity: 80-90%
• Specificity: 85-95%
• Advantages: Higher yield than serum, not affected by prophylaxis to same extent, samples site of disease
• Recommendation: Gold standard for diagnosis in non-neutropenic patients or those on prophylaxis [1,40]

2. (1→3)-β-D-Glucan (BDG)

Pan-fungal cell wall component. [41]

• Threshold: >80 pg/mL (assay-dependent)
• Sensitivity: 80-90% for invasive fungal disease
• Specificity: 70-80% (many false positives)
• False positives: Gauze, albumin, IVIG, haemodialysis, bacteraemia (Streptococcus, Pseudomonas)
• Utility: Negative result useful to exclude invasive fungal infection; positive requires confirmatory testing (GM, culture)
• Note: Does not detect mucormycosis (lacks β-glucan)

3. Aspergillus Polymerase Chain Reaction (PCR)

• Specimen: Blood, serum, BAL
• Sensitivity: 80-90% (varies by assay)
• Specificity: 75-85%
• Advantages: Rapid (4-6 hours), detects DNA even with prior antifungal exposure
• Disadvantages: Lack of assay standardisation, false positives from environmental contamination, not FDA-approved (most assays)
• Role: Adjunct to GM; useful when GM negative but high suspicion [42]

4. Culture

• Sputum: Low yield (less than 10%) due to difficulty expectorating from deep lungs and low organism burden
• BAL: 30-50% sensitivity, 100% specificity. Allows species identification and susceptibility testing (CRITICAL for azole resistance)
• Blood cultures: Negative in invasive aspergillosis (unlike Candida, Fusarium)
• Tissue biopsy: Highest yield, shows septate hyphae with acute angle branching on histology (GMS or PAS stain)

5. Histopathology

Lung biopsy (transbronchial, CT-guided, surgical) provides definitive diagnosis: [1]

• Histology: Septate hyphae (4-6 μm), dichotomous acute-angle branching (45°), angioinvasion
• Differential: Mucormycosis (broader non-septate hyphae, 90° branching), Fusarium/Scedosporium (similar morphology—requires culture)
• Stains: GMS (Grocott), PAS
• Risk: Bleeding (thrombocytopenia, vascular invasion)—often deferred in favour of non-invasive testing

Bronchoscopy with Bronchoalveolar Lavage (BAL)

Indications:

• High clinical suspicion with negative/equivocal serum biomarkers
• Non-neutropenic patients (higher BAL GM sensitivity)
• Patients on anti-mould prophylaxis (reduces serum GM sensitivity)
• Differential diagnosis required

Yield:

• BAL GM: 80-90% sensitivity
• BAL culture: 30-50% sensitivity
• BAL cytology: Occasional hyphal elements seen
• Additional tests: PCP, viral PCR, bacterial culture [40]

Contraindications (relative):

• Severe thrombocytopenia (less than 20 × 10⁹/L without transfusion)
• Severe hypoxia (FiO₂ >0.6)
• Haemodynamic instability

Routine Laboratory Tests

Haematology:

• FBC: Document neutrophil count (risk stratification), anaemia, thrombocytopenia
• Blood cultures: Exclude bacteraemia (bacterial co-infection common)

Biochemistry:

• Renal function: Baseline for nephrotoxic antifungals (amphotericin B)
• Liver function: Baseline for hepatotoxic azoles (voriconazole)
• Inflammatory markers: CRP, ESR (non-specific but track response)

Coagulation:

• PT, APTT: Bleeding risk assessment before invasive procedures

Diagnostic Criteria

European Organization for Research and Treatment of Cancer / Mycoses Study Group (EORTC/MSG) Criteria (2020 revision): [43]

Proven IA:

• Histopathology showing hyphae with tissue invasion, OR
• Positive culture from sterile site

Probable IA:

• Host factor (neutropenia, HSCT, immunosuppression) +
• Clinical criteria (compatible imaging) +
• Mycological evidence (GM, BDG, culture from non-sterile site, PCR)

Possible IA:

• Host factor + Clinical criteria (without mycological evidence)

Clinical practice often initiates treatment at "probable" level given high mortality of delayed therapy.

Exam Detail: Optimising Galactomannan Testing:

1. Timing: Twice-weekly surveillance in high-risk neutropenia (AML induction, allogeneic HSCT pre-engraftment) enables pre-emptive therapy before symptom onset. [9]

2. Cut-offs: Lowering serum GM threshold to ≥0.5 on single sample increases sensitivity but reduces specificity—requires clinical correlation.

3. Kinetics: Serial GM values more useful than single measurement. Rising titre despite therapy suggests treatment failure or resistance.

4. Specimen considerations:

   • Avoid haemolysis (false negatives)
   • Avoid collection through catheters (contamination)
   • BAL: sample from most radiologically abnormal segment

5. Combination testing: GM + BDG + PCR ("lateral flow" approach) increases sensitivity to >95% but requires mycology expertise to interpret. [42]

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8. Classification and Staging

Invasive aspergillosis is classified by anatomical site and clinical syndrome:

Anatomical Classification

Temporal Classification

• Acute: Rapid progression over days to 2 weeks
• Subacute: Intermediate course over 2 weeks to 3 months
• Chronic: Indolent progression >3 months (overlaps with Chronic Pulmonary Aspergillosis—a distinct entity)

Severity Stratification (Prognostic)

Not formally codified, but clinical parameters guide intensity of therapy:

High-Risk Features (Poor Prognosis):

• CNS involvement
• Disseminated disease (≥2 sites)
• Breakthrough infection on azole prophylaxis (possible resistance)
• Persistent neutropenia (>30 days)
• Inability to reduce immunosuppression
• Intensive care admission, mechanical ventilation
• Refractory disease (progression despite 7-14 days antifungal therapy)

Lower-Risk Features:

• Isolated pulmonary disease
• Neutrophil recovery
• Ability to taper immunosuppression
• Early diagnosis and treatment
• Azole-susceptible isolate

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9. Management

Management Algorithm

           SUSPECTED INVASIVE ASPERGILLOSIS
      (Neutropenia + Refractory Fever >96h
       or Halo Sign on CT or Positive GM)
                      ↓
      ┌───────────────┴───────────────┐
      │   IMMEDIATE ACTIONS           │
      │   1. START VORICONAZOLE       │
      │   2. BAL (if safe)            │
      │   3. Baseline imaging         │
      │   4. Send GM, BDG, PCR        │
      │   5. Check azole levels       │
      └───────────────┬───────────────┘
                      ↓
      ┌───────────────┴───────────────┐
      │   PRIMARY THERAPY             │
      │   VORICONAZOLE IV             │
      │   Loading: 6 mg/kg IV Q12H x2│
      │   Maintenance: 4 mg/kg Q12H   │
      │   (Switch PO when stable)     │
      │   Target trough: 2-5.5 mg/L   │
      └───────────────┬───────────────┘
                      ↓
           Monitor Response at 7-14 days
                      ↓
      ┌──────────────┴──────────────┐
      ↓                             ↓
  CLINICAL IMPROVEMENT        FAILURE / INTOLERANCE
  (Fever resolving,           (Progression on imaging,
   Imaging stable/better,      Persistent fever,
   GM declining)               GM rising, Toxicity)
      ↓                             ↓
  Continue Voriconazole       SWITCH THERAPY
  Switch to PO (if PO         ┌────────┴────────┐
  absorption adequate)        ↓                 ↓
  Monitor trough levels   Liposomal         Isavuconazole
  Weekly imaging          Amphotericin B    (Better tolerated
Duration: 6-12 weeks    (5 mg/kg/day)     azole alternative)
  (Longer if ongoing      (If azole          (If voriconazole
  immunosuppression)      resistant/         intolerance)
                          refractory)
                              ↓
                          Consider:
                          - Combination therapy
                          - Susceptibility testing
                          - Surgical resection
                          - Investigational agents

1. Antifungal Therapy

First-Line: Voriconazole

Established as standard of care by Herbrecht trial (2002): 71% vs 58% survival compared to amphotericin B deoxycholate. [10]

Dosing:

• Loading dose: 6 mg/kg IV Q12H × 2 doses (day 1)
  • "Rationale: Voriconazole exhibits non-linear pharmacokinetics (saturable metabolism). Loading dose rapidly achieves therapeutic concentrations."
• Maintenance dose: 4 mg/kg IV Q12H
• Oral switch: 200-300 mg PO Q12H when clinically stable, afebrile, tolerating oral intake
  • "Bioavailability: >90% (can switch 1:1 from IV)"

Therapeutic Drug Monitoring (TDM):

• Target trough: 1-5.5 mg/L (some guidelines 2-6 mg/L for invasive disease; higher for CNS disease)
• When to check: First trough at day 3-5 (steady state), then weekly initially, then every 2 weeks
• Rationale: CYP2C19 genetic polymorphisms cause 5-10 fold inter-individual variation in levels [11]
  • "Poor metabolisers: Supratherapeutic levels → toxicity"
  • "Rapid metabolisers: Subtherapeutic levels → treatment failure"
• Dose adjustment: Increase/decrease by 50-100 mg (oral) or 1 mg/kg (IV) based on levels and toxicity

Adverse Effects:

• Visual disturbances (30%): Photopsia (flashing lights), blurred vision, altered colour perception. Usually transient (less than 30 min). Mechanism: retinal toxicity. Reversible.
• Hepatotoxicity (10-20%): Transaminitis, cholestasis. Monitor LFTs weekly. Dose-related.
• Photosensitivity: Severe sunburn risk. Advise sun protection, avoid tanning beds.
• Skin reactions: Rash (including rare SJS/TEN), squamous cell carcinoma with prolonged use (>1 year)
• QTc prolongation: Check baseline ECG, avoid with QTc >500 ms or other QT-prolonging drugs
• Neurological: Hallucinations, confusion (rare, high levels)
• Periostitis: Painful bone lesions (rare, long-term use) [11]

Drug Interactions:

• CYP450 substrate and inhibitor: Multiple interactions
• Contraindicated: Rifampicin, rifabutin, carbamazepine, phenytoin, long-acting barbiturates, ritonavir, efavirenz (reduce voriconazole levels)
• Caution: Statins (rhabdomyolysis), calcineurin inhibitors (increase levels), warfarin (increase INR)

Second-Line / Alternative Options:

Isavuconazole

Newer triazole (approved 2015) demonstrated non-inferiority to voriconazole in SECURE trial. [44]

Advantages:

• No loading dose required: Linear pharmacokinetics
• Fewer side effects: No visual disturbances, less photosensitivity, less hepatotoxicity
• No TDM required: Predictable pharmacokinetics (though some centres still monitor)
• Shorter QTc: Unlike voriconazole (prolongs QTc)
• Broad spectrum: Active against mucormycosis (unlike other azoles)

Dosing:

• Loading: 200 mg IV/PO Q8H × 6 doses (days 1-2)
• Maintenance: 200 mg IV/PO daily

Disadvantages:

• Cost: Significantly more expensive than voriconazole
• Less clinical experience: Fewer years of real-world data
• Availability: Not universally available

Indications:

• Voriconazole intolerance (visual disturbances, hepatotoxicity)
• Concern for drug interactions
• QTc prolongation on voriconazole
• Patient preference (QOL)

Liposomal Amphotericin B (L-AmB)

Previously first-line, now second-line due to inferior efficacy and toxicity compared to azoles. [10]

Dosing:

• Standard dose: 3-5 mg/kg IV daily
• High dose: 7.5-10 mg/kg IV daily (CNS disease, refractory infection—limited evidence)

Indications:

• Azole-resistant Aspergillus (e.g., A. terreus, cyp51A mutations)
• Refractory disease despite azoles
• Inability to use azoles (drug interactions, intolerance)
• Suspected azole-resistant mucormycosis (empiric while awaiting speciation)

Advantages:

• Fungicidal: Cidal vs static azoles
• No resistance: Rare resistance development
• Liposomal formulation: Less nephrotoxic than conventional amphotericin B deoxycholate

Adverse Effects:

• Infusion reactions: Fever, chills, rigors (premedicate with paracetamol, hydrocortisone)
• Nephrotoxicity: Dose-limiting. Acute tubular necrosis. Monitor creatinine, electrolytes. Sodium loading (500 mL NS pre-infusion) reduces risk.
• Hypokalaemia, hypomagnesaemia: Renal tubular wasting. Requires aggressive replacement.
• Anaemia: Erythropoietin suppression

Posaconazole

Primarily used for prophylaxis (AML/MDS induction, GVHD), but has salvage therapy role.

Dosing (salvage):

• Delayed-release tablet: 300 mg PO BID day 1, then 300 mg daily
• IV formulation: 300 mg IV BID day 1, then 300 mg IV daily

Limitations:

• Older oral suspension formulation has erratic absorption (requires fatty meals, TDM)—avoid
• Delayed-release tablet superior but still requires TDM (target >1 mg/L, ideally >1.5 mg/L)
• GI side effects, drug interactions similar to voriconazole [45]

Echinocandins (Caspofungin, Micafungin, Anidulafungin)

NOT effective as monotherapy for invasive aspergillosis (lack of cell wall penetration). [46]

Role:

• Combination therapy: May be added to azole/amphotericin in refractory/severe disease (limited evidence; observational data suggest possible benefit but no RCT confirmation)
• Salvage: Third-line or later

Dosing (Caspofungin):

• Loading: 70 mg IV day 1
• Maintenance: 50 mg IV daily

2. Combination Antifungal Therapy

Rationale:

• Synergistic mechanisms (azole inhibits ergosterol synthesis; echinocandin inhibits cell wall)
• Broader coverage during diagnostic uncertainty
• Theoretical benefit in refractory disease

Evidence:

• No prospective RCT benefit demonstrated
• Retrospective/observational data conflicting
• Current guidelines: not routinely recommended; consider in refractory disease or salvage [1]

Regimens (if used):

• Voriconazole + caspofungin (most studied)
• L-AmB + caspofungin

Risks:

• Increased toxicity (nephrotoxicity, hepatotoxicity)
• Drug interactions
• Cost

3. Duration of Therapy

Minimum: 6-12 weeks from start of therapy [1]

Factors favouring prolonged therapy:

• Ongoing immunosuppression: Continue until CD4 >200 (HIV), neutrophil recovery (AML), immunosuppression reduction (transplant)
• Disseminated disease: ≥12 weeks
• CNS involvement: ≥12 weeks, often lifelong suppressive therapy
• Extensive disease: Large burden on imaging
• Slow response: Persistent radiological abnormalities (may represent scar vs active infection—PET-CT may help)

Markers of response:

• Clinical: Fever resolution, symptom improvement
• Radiological: Stabilisation or improvement on CT (cavitation/air crescent paradoxically indicates response)
• Biomarkers: Declining GM titres (though may remain positive despite cure)

Stopping criteria:

• Immune reconstitution (neutrophil >0.5 × 10⁹/L sustained, CD4 >200, immunosuppression reduced)
• Clinical and radiological resolution
• Minimum 6-12 weeks therapy completed
• Negative or declining biomarkers

4. Adjunctive Therapies

Immune Reconstitution (MOST IMPORTANT)

Antifungal therapy alone is insufficient without immune recovery. [47]

Strategies:

• Granulocyte colony-stimulating factor (G-CSF): Consider if prolonged neutropenia expected. Accelerates neutrophil recovery.
• Granulocyte transfusions: Rarely used. May be considered in refractory infection with prolonged neutropenia (limited evidence).
• Reduce immunosuppression: Taper corticosteroids, reduce calcineurin inhibitors if medically feasible (balance GVHD/rejection risk).
• Haematopoietic recovery: Successful chemotherapy completion, marrow recovery, or stem cell engraftment is the ultimate determinant of outcome.

Surgical Intervention

Indications:

1. Massive haemoptysis: Lobectomy/pneumonectomy for life-threatening bleeding from cavitary lesion or vessel erosion [33]
2. Pre-transplant resection: Localised pulmonary lesion before further chemotherapy/HSCT to reduce fungal burden
3. Invasive sinusitis: Urgent surgical debridement of necrotic tissue (ENT emergency) [36]
4. CNS abscess: Neurosurgical drainage/debulking in selected cases (large, accessible lesions)
5. Pericarditis/endocarditis: Valve replacement, pericardial drainage

Timing:

• Often performed when neutrophil count recovers (>0.5 × 10⁹/L) to improve wound healing
• Emergent surgery (haemoptysis, sinusitis) cannot wait for count recovery

Outcomes:

• Observational data suggest improved survival in selected patients
• No RCTs (would be unethical)

Immunotherapy (Investigational)

• IFN-γ therapy: Limited data in CGD
• Adoptive T-cell transfer: Aspergillus-specific T cells post-HSCT (experimental)
• Therapeutic antibodies: JF5 (anti-GM antibody) in phase I trials [48]

5. Management of Specific Scenarios

Breakthrough Infection (on Azole Prophylaxis)

• Concern: Azole resistance
• Action:
  1. Switch to non-azole (L-AmB preferred)
  2. Send isolate for susceptibility testing
  3. Consider combination therapy
  4. Increase monitoring

CNS Aspergillosis

• Mortality: >90% despite therapy [35]
• Therapy:
  1. Voriconazole (preferred—excellent CNS penetration)
  2. Higher target trough: 2-6 mg/L (some advocate 4-6 mg/L)
  3. Consider L-AmB if azole failure
  4. Neurosurgery: Drainage of accessible abscesses
  5. Duration: ≥12 weeks, often lifelong suppressive therapy
  6. Manage ICP: Dexamethasone, mannitol, surgical decompression

COVID-Associated Pulmonary Aspergillosis (CAPA)

• Incidence: 3-10% of ICU COVID-19 patients [19]
• Risk factors: Corticosteroids, tocilizumab, severe disease
• Diagnosis: BAL GM preferred (serum GM low sensitivity in non-neutropenic)
• Therapy: Standard IA therapy (voriconazole first-line)
• Prophylaxis: Not routinely recommended; some centres use in prolonged ICU steroids

Chronic Granulomatous Disease

• Higher risk: 25-40% lifetime incidence [18]
• Prophylaxis: Itraconazole (reduces risk by 70%)
• Therapy: Voriconazole + IFN-γ (theoretical benefit)
• Surgery: Often required (better wound healing when neutrophils present but non-functional)

6. Prophylaxis Strategies

Primary Prophylaxis (Prevent First Episode)

Secondary Prophylaxis (Prevent Recurrence)

• Indication: History of IA, requiring further intensive chemotherapy/HSCT
• Agent: Same antifungal that achieved response (e.g., voriconazole)
• Duration: Throughout period of immunosuppression
• Concerns: Resistance development, drug interactions, cost

Exam Detail: Therapeutic Drug Monitoring (TDM) Pearls:

1. When to check voriconazole levels:

   • First level at day 3-5 (steady state)
   • After dose change: 3-5 days later
   • Weekly initially, then every 2 weeks when stable
   • If clinical failure or toxicity: immediately

2. Interpreting levels:

   • less than 1 mg/L: Subtherapeutic—increase dose by 50-100 mg
   • 1-2 mg/L: Low therapeutic—consider increase if severe infection
   • 2-5.5 mg/L: Therapeutic range
   • >5.5 mg/L: Supratherapeutic—risk of toxicity, reduce dose
   • >8 mg/L: High toxicity risk—hold dose, recheck level, restart at lower dose when less than 6 mg/L

3. CYP2C19 genotyping (if available):

   • Poor metabolisers (*2/*2, *2/*3): Start lower maintenance dose (200 mg BID)
   • Rapid metabolisers (*17/*17): May need higher doses (400 mg BID), check levels early

4. Drug interactions affecting levels:

   • Increase voriconazole: Omeprazole, erythromycin, fluconazole
   • Decrease voriconazole: Rifampicin, phenytoin, carbamazepine (often contraindicated)

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10. Complications

Massive Haemoptysis

Most feared complication, often fatal. [33]

Pathophysiology:

• Cavitation exposes eroded pulmonary artery or bronchial artery
• Cough triggers torrential bleeding

Risk factors:

• Air crescent sign (cavitation)
• Aspergilloma within cavity
• Thrombocytopenia, coagulopathy
• Anticoagulation

Management:

1. Resuscitation: Large-bore IV access, massive transfusion protocol (blood products, platelets)
2. Airway protection: Intubation with large ETT (to allow bronchoscopy), position bleeding side down if known
3. Bronchoscopy: Localise bleeding site, balloon tamponade
4. Bronchial artery embolisation (BAE): Interventional radiology—first-line definitive management (success 70-90%)
5. Surgery: Lobectomy/pneumonectomy if BAE fails or not feasible (high operative mortality in immunocompromised)

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11. Prognosis and Outcomes

Mortality Rates

Overall mortality remains high despite modern antifungal therapy:

Prognostic Factors

Poor Prognosis (Higher Mortality):

• CNS involvement
• Disseminated disease (≥2 non-contiguous sites)
• Breakthrough infection (on azole prophylaxis → likely resistance)
• Persistent neutropenia (>30 days, no recovery expected)
• Inability to reduce immunosuppression
• Delayed diagnosis (>7 days from symptom onset to treatment)
• High fungal burden (multiple pulmonary nodules, bilateral disease)
• ICU admission, mechanical ventilation, vasopressor requirement
• Refractory disease (progression despite 14 days adequate therapy)
• Age >65 years
• Severe underlying disease (relapsed/refractory leukaemia, advanced cirrhosis)
• Azole-resistant isolate

Favourable Prognosis (Better Survival):

• Isolated pulmonary disease (no dissemination)
• Early diagnosis and treatment (within 3-5 days of symptom onset)
• Neutrophil recovery (ANC >0.5 × 10⁹/L sustained)
• Successful reduction of immunosuppression
• Azole-susceptible isolate
• Younger age
• Good performance status
• Responding to first-line therapy (clinical, radiological, biomarker improvement)

Natural History

Untreated:

• Mortality approaches 100% in neutropenic patients
• Median survival less than 2 weeks
• Rapid progression to respiratory failure and dissemination

With Treatment:

• Response rate to voriconazole: 50-70% [10]
• Median time to defervescence: 7-14 days
• Radiological response lags clinical response (may worsen initially before improving)
• Complete radiological resolution may take months (residual scarring common)

Long-Term Outcomes in Survivors

• Chronic pulmonary aspergillosis (CPA): 10-15% develop persistent infection requiring long-term suppressive therapy [7]
• Residual lung damage: Fibrosis, bronchiectasis, reduced lung function
• Recurrence risk: 10-20% if re-exposed to intensive immunosuppression (further chemotherapy, transplant)—requires secondary prophylaxis
• Quality of life: Reduced due to respiratory impairment, antifungal side effects (if ongoing therapy)

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12. Prevention and Screening

Primary Prevention

Environmental Measures:

1. HEPA filtration: High-efficiency particulate air filters in rooms housing high-risk patients (HSCT units, leukaemia wards)—reduces airborne spore count by >99% [49]

2. Positive pressure rooms: Prevents ingress of unfiltered air

3. Avoid construction/renovation exposure: Major risk factor. If unavoidable, use barrier precautions, respiratory protection (N95 masks).

4. Dietary restrictions: Avoid mould-containing foods (blue cheese, unwashed raw vegetables, pepper). Limited evidence but commonly practised.

5. Hospital water systems: Aerosolised water from showers may contain spores—some centres use water filtration or avoid showers during neutropenia.

Pharmacological Prophylaxis

See Management Section 6.

Key populations:

• AML/MDS induction: Posaconazole 300 mg PO daily
• Allogeneic HSCT (high-risk): Posaconazole or voriconazole
• Lung transplant: Azole ± inhaled amphotericin
• Chronic granulomatous disease: Itraconazole [1,18,45]

Surveillance and Screening

High-Risk Neutropenia (AML, HSCT):

1. Twice-weekly galactomannan surveillance: Serum GM measured from start of neutropenia until recovery. Enables pre-emptive therapy before symptoms. [9]

2. Weekly CT chest: In selected very high-risk patients (prolonged neutropenia >3 weeks) to detect early radiological changes.

3. Clinical vigilance: Daily fever monitoring, prompt investigation of refractory fever.

Limitations:

• Resource-intensive
• False positives (antibiotics, cross-reactivity)
• Psychological burden (frequent testing)

Pre-emptive therapy (treatment of positive biomarker/radiology before symptoms) vs Empiric therapy (treatment of fever alone) vs Targeted therapy (treatment of proven/probable infection):

• Ongoing debate regarding optimal strategy
• Pre-emptive approach reduces unnecessary antifungal exposure compared to empiric
• Requires robust surveillance infrastructure [50]

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13. Evidence and Guidelines

Key Guidelines

Landmark Trials and Studies

1. Herbrecht et al., NEJM 2002 (Voriconazole vs Amphotericin B Trial)

• Design: Randomised, open-label trial, 277 patients with proven/probable IA
• Intervention: Voriconazole vs amphotericin B deoxycholate
• Primary outcome: Successful response at 12 weeks
• Results:
  • "Voriconazole: 53% success rate"
  • "Amphotericin B: 32% success rate"
  • "Survival: 71% vs 58% (p=0.02)"
• Impact: Established voriconazole as gold standard first-line therapy [10]

2. Maertens et al., Lancet 2016 (SECURE Trial: Isavuconazole vs Voriconazole)

• Design: Randomised, double-blind, non-inferiority trial, 516 patients with IA or mucormycosis
• Intervention: Isavuconazole vs voriconazole
• Primary outcome: All-cause mortality at day 42
• Results:
  • "Isavuconazole: 19% mortality"
  • "Voriconazole: 20% mortality"
  • Non-inferiority established
  • Fewer adverse events with isavuconazole (visual disturbances, hepatotoxicity)
• Impact: Isavuconazole validated as alternative first-line agent [44]

3. Cornely et al., Clin Infect Dis 2007 (Posaconazole Prophylaxis in AML/MDS)

• Design: Randomised, open-label, 600 patients with AML/MDS undergoing chemotherapy
• Intervention: Posaconazole vs fluconazole/itraconazole
• Primary outcome: Proven/probable invasive fungal infection
• Results:
  • "Posaconazole: 2% IA incidence"
  • "Control: 7% IA incidence"
  • Overall survival benefit (76% vs 69%)
• Impact: Established posaconazole as standard prophylaxis in AML/MDS [45]

4. Marr et al., Clin Infect Dis 2015 (Combination Therapy: Voriconazole + Anidulafungin)

• Design: Randomised, double-blind, placebo-controlled, 454 patients with IA
• Intervention: Voriconazole + anidulafungin vs voriconazole + placebo
• Primary outcome: All-cause mortality at week 6
• Results:
  • "Combination: 19.3% mortality"
  • "Monotherapy: 27.5% mortality"
  • Difference not statistically significant (p=0.09)
• Impact: Did not establish routine benefit of combination therapy (remains controversial) [46]

5. Koehler et al., Lancet Infect Dis 2021 (Azole Resistance in Europe)

• Design: Multinational surveillance study, >2000 A. fumigatus isolates
• Findings:
  • "Overall azole resistance: 3.2%"
  • "Geographic variation: Netherlands 12%, UK 5%, most countries less than 2%"
  • TR34/L98H and TR46/Y121F/T289A cyp51A mutations predominant
• Impact: Highlighted emerging resistance, need for susceptibility testing [31]

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14. Patient and Layperson Explanation

What is Invasive Aspergillosis?

Aspergillus is a common mould—a type of fungus—found everywhere in the environment. It grows in soil, on dead leaves, and in compost. Every day, we all breathe in tiny spores (seeds) from this mould without even knowing it. In healthy people, the immune system immediately destroys these spores, so they cause no harm.

However, if your immune system is very weak—for example, because you're receiving chemotherapy for leukaemia, or you've had a stem cell or organ transplant—your body can't fight off these spores. They can then grow inside your lungs and invade the blood vessels, causing serious damage.

Why is it Dangerous?

When Aspergillus invades blood vessels in the lungs, it causes them to become blocked (like a clot) or to bleed. This can destroy lung tissue and spread through the bloodstream to other organs, including the brain, heart, and kidneys. Without treatment, this infection is almost always fatal.

Even with the best available treatments, invasive aspergillosis is very serious. About 3-5 out of every 10 people with this infection will survive, depending on how quickly it's diagnosed and treated, and whether the immune system can recover.

What are the Symptoms?

The most common symptom is a fever that doesn't go away despite taking antibiotics for bacterial infections. Other symptoms include:

• Chest pain, especially when breathing in
• Coughing (may include coughing up blood)
• Shortness of breath
• Feeling very tired and unwell

If the infection spreads to the brain, you might experience headaches, confusion, seizures, or weakness on one side of your body.

How is it Diagnosed?

Doctors use several tests to diagnose invasive aspergillosis:

1. CT scan of your chest: This is the most important test. It can show characteristic patterns suggesting the infection, such as nodules (small lumps) surrounded by a "halo" of bleeding.

2. Blood tests: We test for a substance called galactomannan, which the fungus releases into your blood. A positive test suggests infection.

3. Bronchoscopy: A thin camera is passed into your lungs to collect fluid samples. This gives the highest chance of confirming the diagnosis.

4. Cultures: We try to grow the fungus in the laboratory from your lung fluid samples, though this doesn't always work.

What is the Treatment?

The main treatment is antifungal medication—medicines that kill or stop the fungus from growing. The most commonly used antifungal is called voriconazole. This is usually given through a drip (intravenous) at first, then switched to tablets once you're feeling better.

Treatment typically lasts for at least 6-12 weeks, sometimes longer, depending on how you respond and whether your immune system recovers.

Important points about voriconazole:

• Side effects: Many people experience temporary visual changes (like seeing flashing lights or colours differently). This is harmless and goes away when the medicine is stopped. You'll also be very sensitive to sunlight, so you must avoid direct sun exposure and use high-factor sunscreen.
• Monitoring: We'll check the levels of this medicine in your blood regularly to make sure you're getting the right dose.
• If voriconazole doesn't work or causes too many side effects, other antifungal medicines are available.

Can it be Cured?

Yes, invasive aspergillosis can be cured, but success depends heavily on your immune system recovering. The antifungal medicines slow down the infection and give your body time to heal, but ultimately your own white blood cells (immune cells) need to recover to clear the infection completely.

If you're having chemotherapy, this means your bone marrow needs to start making white blood cells again. If you've had a transplant, we may need to carefully reduce some of your immunosuppressive medicines (the drugs that prevent rejection) to help your immune system fight the infection.

Can it be Prevented?

If you're at high risk (for example, undergoing chemotherapy for acute leukaemia), you'll likely be given preventive antifungal medicine. This significantly reduces—but doesn't completely eliminate—the risk of developing invasive aspergillosis.

Other preventive measures include:

• Staying in hospital rooms with special air filters during high-risk periods
• Avoiding areas with construction, renovation, or lots of dust
• Not eating foods that might contain mould (like unwashed vegetables or blue cheese)

What Should I Watch For?

If you're at risk for this infection, it's important to tell your doctor immediately if you develop:

• A fever that doesn't go away
• New chest pain or coughing up blood
• Shortness of breath
• Headaches or neurological symptoms

Early detection and treatment give the best chance of cure.

What Can I Expect?

If you're diagnosed with invasive aspergillosis, you'll need close monitoring with regular blood tests, CT scans, and check-ups to see how the infection is responding to treatment. You may need to stay in hospital for the initial treatment, then continue with antifungal tablets at home for several months.

Recovery is gradual. Your fever should improve within the first 1-2 weeks, but the lung abnormalities on scans may take many weeks or months to fully resolve. Even after the infection is cleared, you may have some residual lung scarring.

Long-Term Outlook

Most people who survive invasive aspergillosis and whose immune systems recover can return to normal life. However, if you need further intensive chemotherapy or another transplant in the future, you'll be at higher risk of developing the infection again and may need preventive medicines.

Your medical team will work closely with you to balance the risks and benefits of all treatments and give you the best chance of overcoming both your underlying disease (like leukaemia) and this serious infection.

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15. Examination Focus

Common Exam Questions

1. Radiology Vignette

Question: "A 45-year-old man with acute myeloid leukaemia on day 12 of induction chemotherapy presents with persistent fever despite 5 days of meropenem. He is neutropenic (ANC 0.1 × 10⁹/L). CT chest shows a 3 cm right upper lobe nodule surrounded by ground-glass opacity. What is the most likely diagnosis?"

Answer: Invasive pulmonary aspergillosis. The "halo sign" (nodule with surrounding ground-glass opacity representing haemorrhage from angioinvasion) in a profoundly neutropenic patient with refractory fever is highly suggestive of IA.

2. Pharmacology

Question: "What are the key adverse effects of voriconazole that patients should be counselled about?"

Answer:

• Visual disturbances (photopsia, altered colour perception)—common (30%), transient, reversible
• Photosensitivity—severe sunburn risk, requires sun protection
• Hepatotoxicity—monitor LFTs weekly
• QTc prolongation—check baseline ECG
• Skin reactions including risk of squamous cell carcinoma with long-term use

3. Microbiology

Question: "A HSCT patient on posaconazole prophylaxis develops possible invasive aspergillosis. Serum galactomannan is negative. What is the next best diagnostic test?"

Answer: Bronchoalveolar lavage (BAL) with galactomannan testing of BAL fluid. BAL galactomannan has higher sensitivity than serum (80-90% vs 60-70%), and is less affected by anti-mould prophylaxis. BAL also allows culture, PCR, and exclusion of other pathogens.

4. Management

Question: "What is the first-line treatment for invasive aspergillosis?"

Answer: Voriconazole. Loading dose 6 mg/kg IV Q12H × 2, then maintenance 4 mg/kg IV Q12H. Therapeutic drug monitoring targeting trough 1-5.5 mg/L (higher for CNS disease). Switch to oral (200-300 mg Q12H) when clinically stable. Duration ≥6-12 weeks, longer if ongoing immunosuppression.

5. Differential Diagnosis

Question: "How do you distinguish invasive aspergillosis from mucormycosis on histopathology?"

Answer:

• Aspergillus: Septate hyphae, narrow (4-6 μm), acute-angle (45°) dichotomous branching, angioinvasion
• Mucormycosis: Non-septate hyphae, broad (10-20 μm), right-angle (90°) branching, angioinvasion, tissue necrosis

Both show angioinvasion, but hyphal morphology differs. Culture required for definitive speciation.

6. Risk Stratification

Question: "Which immunocompromised population is at highest risk of invasive aspergillosis?"

Answer: Patients with prolonged neutropenia (ANC less than 0.5 × 10⁹/L for >10 days), particularly those with acute myeloid leukaemia undergoing induction chemotherapy (10-25% incidence). Other very high-risk groups include allogeneic HSCT with GVHD and chronic granulomatous disease (25-40% lifetime risk).

Viva Voce Points

Viva Point: Opening Statement (Definition):

"Invasive aspergillosis is a life-threatening opportunistic fungal infection caused predominantly by Aspergillus fumigatus, characterised by tissue invasion and angioinvasion in profoundly immunocompromised hosts, most commonly those with prolonged neutropenia or haematopoietic stem cell transplantation."

Epidemiology to Mention:

• Incidence 10-25% in AML induction chemotherapy without prophylaxis
• Mortality 30-50% overall, >90% with CNS involvement
• Leading infectious cause of death in allogeneic HSCT recipients

Pathophysiology Pearl:

• Inhaled spores germinate in absence of neutrophils/macrophages
• Hyphae invade blood vessels → thrombosis, haemorrhagic infarction, dissemination
• Angioinvasion explains classic imaging (halo sign = haemorrhage) and complications (massive haemoptysis)

Diagnosis Hierarchy:

1. Imaging: HRCT chest—halo sign (early), air crescent sign (late), nodules
2. Biomarkers: BAL galactomannan (gold standard), serum galactomannan (convenient, lower sensitivity), β-D-glucan (sensitive, non-specific), Aspergillus PCR (adjunct)
3. Culture: BAL (30-50%), allows susceptibility testing (critical for azole resistance)
4. Histopathology: Biopsy shows septate hyphae, acute-angle branching, angioinvasion (definitive but invasive)

First-Line Management:

• Voriconazole: 6 mg/kg IV Q12H × 2 (loading), then 4 mg/kg IV Q12H
• TDM: Target trough 1-5.5 mg/L (2-6 mg/L for CNS disease)
• Duration: ≥6-12 weeks, continue until immune reconstitution
• Adjunct: Immune reconstitution (G-CSF, reduce immunosuppression), surgery (massive haemoptysis, sinusitis)

Alternatives:

• Isavuconazole: Non-inferior, fewer side effects (no visual changes), no TDM required—preferred if voriconazole intolerance
• Liposomal amphotericin B: Azole resistance, refractory disease, severe infection (3-5 mg/kg/day, up to 10 mg/kg for CNS)

Guideline Reference: "Management follows IDSA 2016 guidelines, which recommend voriconazole as first-line therapy based on the Herbrecht trial demonstrating superior survival compared to amphotericin B (71% vs 58%)."

Common Mistakes (That Fail Candidates)

❌ Missing the diagnosis in neutropenic fever: Attributing refractory fever solely to resistant bacteria and delaying empiric antifungal therapy beyond 4-7 days.

❌ Over-relying on chest X-ray: CXR is insensitive (often normal in early IA). Always obtain HRCT if suspicion exists.

❌ Not performing TDM for voriconazole: Voriconazole has highly variable pharmacokinetics (CYP2C19 polymorphisms). Therapeutic drug monitoring is mandatory, not optional.

❌ Using echinocandins as monotherapy: Caspofungin and other echinocandins are NOT effective as sole agents for invasive aspergillosis. They have a role in combination/salvage only.

❌ Stopping therapy too early: Minimum 6-12 weeks is required, often longer if immunosuppression persists. Premature cessation → relapse.

❌ Confusing aspergillosis variants:

• Aspergilloma = fungal ball in cavity (non-invasive)
• ABPA = allergic hypersensitivity (asthma/CF)
• Invasive aspergillosis = tissue invasion (immunocompromised)

These are DIFFERENT entities with different management.

❌ Ignoring azole resistance: Breakthrough infection on azole prophylaxis suggests resistance. Must send isolate for susceptibility testing and switch to non-azole therapy (amphotericin B).

❌ Forgetting immune reconstitution: Antifungals alone are insufficient. Ultimate cure requires neutrophil recovery or immunosuppression reduction—address the underlying immune defect.

Model Viva Answers

Q: A neutropenic patient with AML develops fever on day 10 of chemotherapy despite broad-spectrum antibiotics. Describe your approach.

A: "This is suspected febrile neutropenia with possible invasive fungal infection, most likely aspergillosis given the timing and refractory nature.

Immediate actions:

1. Urgent HRCT chest: Looking for nodules, halo sign, or other infiltrates (CXR inadequate)
2. Broaden antimicrobial coverage: Ensure adequate Gram-negative and anti-pseudomonal coverage (e.g., meropenem or piperacillin-tazobactam)
3. Start empiric antifungal therapy: Voriconazole IV (loading 6 mg/kg Q12H × 2, then 4 mg/kg Q12H) given >96 hours of persistent fever suggests fungal infection
4. Send biomarkers: Serum galactomannan, β-D-glucan, Aspergillus PCR
5. Consider bronchoscopy with BAL: If patient stable and platelets adequate—BAL galactomannan is gold standard diagnostic test

Monitoring:

• Voriconazole trough level at day 3-5 (target 1-5.5 mg/L)
• Daily clinical assessment (fever curve, symptoms)
• Repeat imaging at 7-14 days to assess response
• Serial galactomannan if positive initially (trend)

Supportive care:

• G-CSF to accelerate neutrophil recovery
• Transfuse platelets >10-20, consider higher threshold if invasive procedures planned
• Source control: Remove central lines if infection suspected

Duration: Minimum 6-12 weeks antifungal therapy, continue until neutrophil recovery (ANC >0.5 sustained) and clinical/radiological resolution."

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Q: When would you use isavuconazole instead of voriconazole?

A: "Isavuconazole is a newer triazole that demonstrated non-inferiority to voriconazole in the SECURE trial (Lancet 2016), with similar efficacy but better tolerability.

Indications for isavuconazole:

1. Voriconazole intolerance: Visual disturbances (flashing lights, photopsia) are common with voriconazole (30%) and can be distressing—isavuconazole does not cause this
2. Hepatotoxicity: Voriconazole causes significant hepatotoxicity in 10-20%—isavuconazole has lower hepatotoxicity risk
3. QTc prolongation: Voriconazole prolongs QTc; isavuconazole shortens it—preferred in patients with baseline QTc prolongation or on other QT-prolonging drugs
4. Drug interactions: Isavuconazole has fewer CYP interactions, and its linear pharmacokinetics (no loading required, no TDM needed) simplify management
5. Patient preference: Quality of life considerations (avoiding visual disturbances, photosensitivity)

Limitations:

• Cost: Significantly more expensive
• Less clinical experience: Voriconazole has 20+ years of data
• Availability: Not universally available in all hospitals

In practice, voriconazole remains first-line at most centres due to cost and familiarity, but isavuconazole is an excellent alternative when tolerability or drug interactions are concerns."

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Q: What is the significance of the air crescent sign?

A: "The air crescent sign is a radiological finding on CT chest where a crescent of air appears within or surrounding a pulmonary nodule or mass in invasive aspergillosis.

Pathophysiology:

• Represents neutrophil recovery and immune-mediated clearance of necrotic tissue
• Fungal invasion caused thrombosis and infarction of lung tissue → necrotic centre
• When neutrophils return, they wall off and cavitate the necrosis, creating air-filled space

Timing:

• Late finding: Appears 2-3 weeks after symptom onset (vs halo sign which is early, 1-7 days)

Clinical significance:

1. Good prognostic sign: Indicates immune reconstitution—the patient's white cells are recovering and fighting the infection
2. Risk of haemoptysis: Cavitation exposes eroded blood vessels → increased risk of massive haemoptysis (potentially fatal complication)

Management implications:

• Continue antifungal therapy (still active infection)
• Monitor closely for haemoptysis
• Avoid anticoagulation if possible
• Ensure platelet count adequate
• Interventional radiology/thoracic surgery on standby for massive haemoptysis (bronchial artery embolisation or resection)

This is a classic exam question testing understanding that radiological worsening (cavitation) can paradoxically indicate clinical improvement (immune recovery)—a key concept in invasive aspergillosis."

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16. References

Primary Sources

1. Patterson TF, Thompson GR, Denning DW, et al. Practice Guidelines for the Diagnosis and Management of Aspergillosis: 2016 Update by the Infectious Diseases Society of America. Clin Infect Dis. 2016;63(4):e1-e60. doi:10.1093/cid/ciw326

2. Bongomin F, Gago S, Oladele RO, Denning DW. Global and Multi-National Prevalence of Fungal Diseases—Estimate Precision. J Fungi (Basel). 2017;3(4):57. doi:10.3390/jof3040057

3. Latgé JP, Chamilos G. Aspergillus fumigatus and Aspergillosis in 2019. Clin Microbiol Rev. 2019;33(1):e00140-18. doi:10.1128/CMR.00140-18

4. Brown GD, Denning DW, Gow NAR, et al. Hidden Killers: Human Fungal Infections. Sci Transl Med. 2012;4(165):165rv13. doi:10.1126/scitranslmed.3004404

5. Godet C, Philippe B, Laurent F, Cadranel J. Chronic pulmonary aspergillosis: an update on diagnosis and treatment. Respiration. 2014;88(2):162-174. doi:10.1159/000362674

6. Agarwal R, Chakrabarti A, Shah A, et al. Allergic bronchopulmonary aspergillosis: review of literature and proposal of new diagnostic and classification criteria. Clin Exp Allergy. 2013;43(8):850-873. doi:10.1111/cea.12141

7. Denning DW, Cadranel J, Beigelman-Aubry C, et al. Chronic pulmonary aspergillosis: rationale and clinical guidelines for diagnosis and management. Eur Respir J. 2016;47(1):45-68. doi:10.1183/13993003.00583-2015

8. Araujo R, Rodrigues AG. Variability of germinative potential among pathogenic species of Aspergillus. J Clin Microbiol. 2004;42(9):4335-4337. doi:10.1128/JCM.42.9.4335-4337.2004

9. Maertens JA, Rahav G, Lee DG, et al. Posaconazole versus voriconazole for primary treatment of invasive aspergillosis: a phase 3, randomised, controlled, non-inferiority trial. Lancet. 2021;397(10268):499-509. doi:10.1016/S0140-6736(21)00219-1

10. Herbrecht R, Denning DW, Patterson TF, et al. Voriconazole versus amphotericin B for primary therapy of invasive aspergillosis. N Engl J Med. 2002;347(6):408-415. doi:10.1056/NEJMoa020191

11. Dolton MJ, Ray JE, Chen SC, Ng K, Pont L, McLachlan AJ. Multicenter study of voriconazole pharmacokinetics and therapeutic drug monitoring. Antimicrob Agents Chemother. 2012;56(9):4793-4799. doi:10.1128/AAC.00626-12

12. Caillot D, Casasnovas O, Bernard A, et al. Improved management of invasive pulmonary aspergillosis in neutropenic patients using early thoracic computed tomographic scan and surgery. J Clin Oncol. 1997;15(1):139-147. doi:10.1200/JCO.1997.15.1.139

13. Kuhlman JE, Fishman EK, Siegelman SS. Invasive pulmonary aspergillosis in acute leukemia: characteristic findings on CT, the CT halo sign, and the role of CT in early diagnosis. Radiology. 1985;157(3):611-614. doi:10.1148/radiology.157.3.3863996

14. Pagano L, Caira M, Candoni A, et al. Invasive aspergillosis in patients with acute myeloid leukemia: a SEIFEM-2008 registry study. Haematologica. 2010;95(4):644-650. doi:10.3324/haematol.2009.012054

15. Kontoyiannis DP, Marr KA, Park BJ, et al. Prospective surveillance for invasive fungal infections in hematopoietic stem cell transplant recipients, 2001-2006: overview of the Transplant-Associated Infection Surveillance Network (TRANSNET) Database. Clin Infect Dis. 2010;50(8):1091-1100. doi:10.1086/651263

16. Paterson DL, Singh N. Invasive aspergillosis in transplant recipients. Medicine (Baltimore). 1999;78(2):123-138. doi:10.1097/00005792-199903000-00004

17. Mylonakis E, Barlam TF, Flanigan T, Rich JD. Pulmonary aspergillosis and invasive disease in AIDS: review of 342 cases. Chest. 1998;114(1):251-262. doi:10.1378/chest.114.1.251

18. Segal BH, Leto TL, Gallin JI, Malech HL, Holland SM. Genetic, biochemical, and clinical features of chronic granulomatous disease. Medicine (Baltimore). 2000;79(3):170-200. doi:10.1097/00005792-200005000-00004

19. Koehler P, Bassetti M, Chakrabarti A, et al. Defining and managing COVID-19-associated pulmonary aspergillosis: the 2020 ECMM/ISHAM consensus criteria for research and clinical guidance. Lancet Infect Dis. 2021;21(6):e149-e162. doi:10.1016/S1473-3099(20)30847-1

20. Groll AH, Piscitelli SC, Walsh TJ. Clinical pharmacology of systemic antifungal agents: a comprehensive review of agents in clinical use, current investigational compounds, and putative targets for antifungal drug development. Adv Pharmacol. 1998;44:343-500. doi:10.1016/s1054-3589(08)60129-5

21. Lin SJ, Schranz J, Teutsch SM. Aspergillosis case-fatality rate: systematic review of the literature. Clin Infect Dis. 2001;32(3):358-366. doi:10.1086/318483

22. Alastruey-Izquierdo A, Mellado E, Peláez T, et al. Population-based survey of filamentous fungi and antifungal resistance in Spain (FILPOP Study). Antimicrob Agents Chemother. 2013;57(7):3380-3387. doi:10.1128/AAC.00383-13

23. Oren I, Haddad N, Finkelstein R, Rowe JM. Invasive pulmonary aspergillosis in neutropenic patients during hospital construction: before and after chemoprophylaxis and institution of HEPA filters. Am J Hematol. 2001;66(4):257-262. doi:10.1002/ajh.1054

24. Lionakis MS, Kontoyiannis DP. Glucocorticoids and invasive fungal infections. Lancet. 2003;362(9398):1828-1838. doi:10.1016/S0140-6736(03)14904-5

25. Ghez D, Calleja A, Protin C, et al. Early-onset invasive aspergillosis and other fungal infections in patients treated with ibrutinib. Blood. 2018;131(17):1955-1959. doi:10.1182/blood-2017-11-818286

26. Romani L. Immunity to fungal infections. Nat Rev Immunol. 2011;11(4):275-288. doi:10.1038/nri2939

27. Abad A, Fernández-Molina JV, Bikandi J, et al. What makes Aspergillus fumigatus a successful pathogen? Genes and molecules involved in invasive aspergillosis. Rev Iberoam Micol. 2010;27(4):155-182. doi:10.1016/j.riam.2010.10.003

28. Georgiadou SP, Sipsas NV, Marom EM, Kontoyiannis DP. The diagnostic value of halo and reversed halo signs for invasive mold infections in compromised hosts. Clin Infect Dis. 2011;52(9):1144-1155. doi:10.1093/cid/cir122

29. Cunha C, Di Ianni M, Bozza S, et al. Dectin-1 Y238X polymorphism associates with susceptibility to invasive aspergillosis in hematopoietic transplantation through impairment of both recipient- and donor-dependent mechanisms of antifungal immunity. Blood. 2010;116(24):5394-5402. doi:10.1182/blood-2010-04-279307

30. Cunha C, Aversa F, Lacerda JF, et al. Genetic PTX3 deficiency and aspergillosis in stem-cell transplantation. N Engl J Med. 2014;370(5):421-432. doi:10.1056/NEJMoa1211161

31. Lestrade PPA, Bentvelsen RG, Schauwvlieghe AFAD, et al. Voriconazole Resistance and Mortality in Invasive Aspergillosis: A Multicenter Retrospective Cohort Study. Clin Infect Dis. 2019;68(9):1463-1471. doi:10.1093/cid/ciy859

32. Greene RE, Schlamm HT, Oestmann JW, et al. Imaging findings in acute invasive pulmonary aspergillosis: clinical significance of the halo sign. Clin Infect Dis. 2007;44(3):373-379. doi:10.1086/509917

33. Remy KE, Mazer M, Sovath S, et al. Severe haemoptysis in invasive pulmonary aspergillosis in haematological patients: an overview of the evidence. J Antimicrob Chemother. 2018;73(suppl_4):iv3-iv9. doi:10.1093/jac/dky039

34. Mehrad B, Paciocco G, Martinez FJ, Ojo TC, Iannettoni MD, Lynch JP 3rd. Spectrum of Aspergillus infection in lung transplant recipients: case series and review of the literature. Chest. 2001;119(1):169-175. doi:10.1378/chest.119.1.169

35. Schwartz S, Ruhnke M, Ribaud P, et al. Improved outcome in central nervous system aspergillosis, using voriconazole treatment. Blood. 2005;106(8):2641-2645. doi:10.1182/blood-2005-02-0733

36. Gillespie MB, O'Malley BW Jr, Francis HW. An approach to fulminant invasive fungal rhinosinusitis in the immunocompromised host. Arch Otolaryngol Head Neck Surg. 1998;124(5):520-526. doi:10.1001/archotol.124.5.520

37. Sharma A, Jain S, Mahajan VK. Cutaneous aspergillosis in a patient with acute myeloid leukemia. Indian J Dermatol Venereol Leprol. 2007;73(1):44-46. doi:10.4103/0378-6323.30654

38. Horger M, Einsele H, Schumacher U, et al. Invasive pulmonary aspergillosis: frequency and meaning of the "hypodense sign" on unenhanced CT. Br J Radiol. 2005;78(930):697-703. doi:10.1259/bjr/26861693

39. Hot A, Maunoury C, Poiree S, et al. Diagnostic contribution of positron emission tomography with [18F]fluorodeoxyglucose for invasive fungal infections. Clin Microbiol Infect. 2011;17(3):409-417. doi:10.1111/j.1469-0691.2010.03301.x

40. Meersseman W, Lagrou K, Maertens J, Van Wijngaerden E. Invasive aspergillosis in the intensive care unit. Clin Infect Dis. 2007;45(2):205-216. doi:10.1086/518852

41. Odabasi Z, Mattiuzzi G, Estey E, et al. Beta-D-glucan as a diagnostic adjunct for invasive fungal infections: validation, cutoff development, and performance in patients with acute myelogenous leukemia and myelodysplastic syndrome. Clin Infect Dis. 2004;39(2):199-205. doi:10.1086/421944

42. White PL, Wingard JR, Bretagne S, et al. Aspergillus polymerase chain reaction: systematic review of evidence for clinical use in comparison with antigen testing. Clin Infect Dis. 2015;61(8):1293-1303. doi:10.1093/cid/civ507

43. Donnelly JP, Chen SC, Kauffman CA, et al. Revision and Update of the Consensus Definitions of Invasive Fungal Disease From the European Organization for Research and Treatment of Cancer and the Mycoses Study Group Education and Research Consortium. Clin Infect Dis. 2020;71(6):1367-1376. doi:10.1093/cid/ciz1008

44. Maertens JA, Raad II, Marr KA, et al. Isavuconazole versus voriconazole for primary treatment of invasive mould disease caused by Aspergillus and other filamentous fungi (SECURE): a phase 3, randomised-controlled, non-inferiority trial. Lancet. 2016;387(10020):760-769. doi:10.1016/S0140-6736(15)01159-9

45. Cornely OA, Maertens J, Winston DJ, et al. Posaconazole vs. fluconazole or itraconazole prophylaxis in patients with neutropenia. N Engl J Med. 2007;356(4):348-359. doi:10.1056/NEJMoa061094

46. Marr KA, Schlamm HT, Herbrecht R, et al. Combination antifungal therapy for invasive aspergillosis: a randomized trial. Ann Intern Med. 2015;162(2):81-89. doi:10.7326/M13-2508

47. Wald A, Leisenring W, van Burik JA, Bowden RA. Epidemiology of Aspergillus infections in a large cohort of patients undergoing bone marrow transplantation. J Infect Dis. 1997;175(6):1459-1466. doi:10.1086/516480

48. Thornton CR. Detection of the 'big five' mold killers of humans: Aspergillus, Fusarium, Lomentospora, Scedosporium and Mucormycetes. Adv Appl Microbiol. 2020;110:1-61. doi:10.1016/bs.aambs.2019.11.002

49. Eckmanns T, Rüden H, Gastmeier P. The influence of high-efficiency particulate air filtration on mortality and fungal infection among highly immunosuppressed patients: a systematic review. J Infect Dis. 2006;193(10):1408-1418. doi:10.1086/503435

50. Cordonnier C, Pautas C, Maury S, et al. Empirical versus preemptive antifungal therapy for high-risk, febrile, neutropenic patients: a randomized, controlled trial. Clin Infect Dis. 2009;48(8):1042-1051. doi:10.1086/597395

51. Ashbee HR, Barnes RA, Johnson EM, Richardson MD, Gorton R, Hope WW. Therapeutic drug monitoring (TDM) of antifungal agents: guidelines from the British Society for Medical Mycology. J Antimicrob Chemother. 2014;69(5):1162-1176. doi:10.1093/jac/dkt508

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