Undifferentiated fever and fever without a source in infants and children — formative case

Station status

This is one MedVellum formative structured clinical encounter. The scoring, prompts and performance descriptions are educational feedback tools. They are not an official college station, timing, mark allocation, pass score or reproduced examination format. [6] [13]

Candidate instructions

You are the paediatric registrar in a regional emergency department. Liam is 40 days old and has been brought by his mother with a fever of 38.9 °C measured at home. His mother reports he has been fussier than usual and feeding less over the past 12 hours. She is worried because "he feels very hot." [6]

Conduct a focused history and examination (using actor cues provided by the assessor). Risk-stratify Liam by age and clinical appearance. Select appropriate investigations and justify your choices. State your empiric management if any is required. Construct a safe disposition plan with a specific written safety-net. Communicate clearly with the mother throughout. [1] [6] [13]

Room setup and observable starting state

The encounter. Liam is a 40-day-old infant born at 39 weeks gestation, weighing 4.2 kg. His mother has brought him to the emergency department. The assessor will supply clinical findings at each stage as the candidate progresses. Liam is represented by the assessor's verbal updates — no physical examination of a real or simulated infant is required. [6]

Simulation safety. State what you would examine and what you would look for, rather than performing painful or distressing procedures. The assessor will provide results. [6]

Actor cues

Caregiver (mother)

• Opening statement: "He has been really hot since this morning. He is not feeding like he usually does and he seems more cranky."
• If asked about fever: "I measured it under his arm — it was 38.9 degrees. He has not had anything for it yet."
• If asked about feeding: "He usually takes about 120 mL every 3 hours. Today he has only had about 60 mL in the last two feeds and seems to struggle."
• If asked about wet nappies: "He has had maybe 3 wet nappies today — fewer than usual but still some."
• If asked about immunisations: "He had his 6-week needles yesterday — that is scheduled here at 6 weeks."
• If asked about sick contacts: "His older sister has a cold. No one else is sick that I know of."
• If asked about pregnancy and birth: "He was born at 39 weeks by normal delivery. No problems. I did not have any infections in pregnancy."
• If the candidate explains the plan well: Express understanding and ask "So when should I bring him back?" [6]

Assessor

Provide the following clinical findings only when the candidate reaches that stage of assessment. Do not volunteer information. [1] [6]

Assessor cues and clinical data

Key decision points

Decision point 1: Risk classification

The candidate must correctly identify that Liam is in the 29-90 day age band with a moderate baseline SBI risk of approximately 3-8%. The candidate must state that age overrides appearance in this age group — a well-appearing infant can still have SBI. The candidate must apply a prediction rule (PECARN or local equivalent). [1] [6]

Decision point 2: Investigation selection

The candidate must request urinalysis and urine culture by catheterisation or SPA (not bag). The candidate must request blood tests (WCC, CRP, procalcitonin if available) and blood culture. The candidate must address whether LP is indicated — under PECARN, it is not required for a low-risk, well-appearing infant with reassuring biomarkers. [1] [6]

Decision point 3: Risk-stratification result

Using the PECARN rule: PCT 0.3 ng/mL (below 1.7 threshold), CRP 6 mg/L (below 20 threshold), ANC 1.5 x 10⁹/L (normal), urinalysis negative. This infant meets low-risk criteria. The candidate must state this clearly and explain what it means. [1]

Decision point 4: Disposition

The candidate must decide between outpatient management without antibiotics (with safety-net and 24-hour follow-up) or a single dose of ceftriaxone with 24-hour review. The candidate must address the social context: Can the mother return? Is follow-up assured? The safety-net must be specific and written. [6] [13]

Communication task

The candidate must explain the plan to the mother clearly and check understanding. This includes: [6] [13]

• Why Liam is being investigated (his age puts him at higher risk)
• What the results show (reassuring so far)
• What happens next (discharge with close follow-up, or observation)
• The specific safety-net: when to return immediately (fever not improving, irritability, poor feeding, rash, reduced wet nappies, any concern)
• Follow-up arrangement within 24 hours [6] [13]

Marking domains

Debrief points

After the encounter, discuss: [6]

1. Why the urine collection method matters — bag specimens have 30% contamination rates; catheter or SPA is mandatory for non-toilet-trained children. [6]
2. When the PECARN rule should NOT be applied — ill-appearing infants, infants with focal findings, immunocompromised infants. Prediction rules apply only to well-appearing infants. [1]
3. The role of enterovirus PCR — in summer and autumn, enterovirus PCR on CSF (if LP performed) or blood can confirm a viral cause and shorten hospital stay. [19]
4. What would change the disposition — if the procalcitonin had been 2.0 ng/mL, the infant would be high-risk regardless of appearance, requiring LP, empiric ceftriaxone and admission. [1] [9]