Diabetes Mellitus — Written Clinical Reasoning

SAQ 1 — Integrated Management (20 marks, 30 minutes)

Prompt: Outline your integrated management plan for this patient, addressing glycaemic control, cardiovascular risk reduction, nephropathy, neuropathy, retinopathy, and the diabetic foot ulcer. Justify each pharmacological decision with reference to evidence. [1]

Model Answer

Problem list (4 marks):

1. Type 2 diabetes with suboptimal glycaemic control (HbA1c 71 mmol/mol) on two oral agents
2. Diabetic nephropathy — stage 3B CKD (eGFR 42) with albuminuria (ACR 18 mg/mmol)
3. Ischaemic heart disease (NSTEMI 2 years ago, DES to RCA) — established ASCVD
4. Diabetic peripheral neuropathy with loss of protective sensation
5. Diabetic foot ulcer — neuropathic plantar ulcer under right first metatarsal head
6. Background diabetic retinopathy (microaneurysms, dot-blot haemorrhages)
7. Hypertension (148/86) — above target for a proteinuric diabetic patient
8. Obesity (BMI 33)
9. Occupation — commercial driver (hypoglycaemia and visual acuity implications) [1]

Glycaemic and pharmacological management (8 marks): [1]

This patient has established atherosclerotic cardiovascular disease (prior NSTEMI), diabetic nephropathy with albuminuria, and obesity — three factors that mandate an organ-protective agent, not just a glucose-lowering agent. The modern hierarchy: [1]

Target HbA1c: 53 to 58 mmol/mol (7.0 to 7.5%). He has established ASCVD and CKD but is relatively young (64) and active — a moderate target. Avoid aggressive targets below 48 given his occupation (hypoglycaemia while driving is catastrophic) and the ACCORD harm signal in patients with established cardiovascular disease. [1]

Cardiovascular risk reduction (3 marks):

• Blood pressure: target below 130/80 (albuminuric diabetic). Start ramipril 2.5mg daily (or any ACE inhibitor) — renoprotective in albuminuria, independent of blood pressure. Monitor creatinine and potassium at 1 to 2 weeks (accept rise up to 30%). Do not combine ACEi and ARB (ONTARGET harm).
• Lipids: already on atorvastatin 40mg — consider intensifying to 80mg (high-intensity statin for secondary prevention). All diabetics with established ASCVD should be on high-intensity statin.
• Antiplatelet: he should be on aspirin 100mg daily for secondary prevention (post-NSTEMI). Confirm adherence. Clopidogrel if aspirin-intolerant.
• Lifestyle: weight loss (GLP-1 RA will help), Mediterranean diet, 150 min/week exercise, smoking status (confirm). [1]

Nephropathy (2 marks):

• ACE inhibitor (ramipril) — reduces intraglomerular pressure and albuminuria.
• SGLT2 inhibitor (dapagliflozin) — DAPA-CKD showed 39% reduction in renal composite.
• Monitor eGFR and urine ACR every 3 to 6 months. Refer to nephrology if eGFR falls below 30 or rapid decline.
• Blood pressure target below 130/80. [1]

Diabetic foot ulcer (2 marks):

• This is a neuropathic plantar ulcer (palpable pulses implied by the scenario; loss of protective sensation; callus; no surrounding erythema suggesting no active infection).
• Offloading: total contact cast is the gold standard for plantar neuropathic ulcers.
• Debridement: sharp debridement of surrounding callus by a podiatrist or foot clinic.
• Wound care: appropriate dressing; monitor for infection.
• Multidisciplinary foot clinic referral — mandatory.
• Assess for ischaemia: ankle-brachial index (may be falsely elevated due to medial calcinosis — use toe pressures if abnormal), palpate pulses.
• Probe-to-bone test — if bone is reached, osteomyelitis is likely; confirm with MRI. [1]

Retinopathy and neuropathy (1 mark):

• Retinopathy: refer to ophthalmology for formal assessment. Background retinopathy — annual surveillance. Note: rapid glycaemic improvement can worsen retinopathy early — screen closely during therapy escalation.
• Neuropathy: loss of protective sensation confirmed — foot education, daily foot inspection, appropriate footwear (offloading insoles). Screen for autonomic neuropathy (orthostatic hypotension, erectile dysfunction, gastroparesis symptoms). [1]

SAQ 2 — Classification Dilemma (10 marks, 15 minutes)

Prompt: A 34-year-old woman, BMI 23, presents with new-onset diabetes (HbA1c 72 mmol/mol). She has lost 6 kg over 3 months with polyuria and nocturia. Her mother has type 1 diabetes and her aunt has autoimmune thyroiditis. She is not on any diabetes medications. How would you classify her diabetes and what investigations would you order? [1]

Model Answer

Clinical reasoning (3 marks): [1]

This presentation is atypical for classical type 2 diabetes and raises the possibility of latent autoimmune diabetes in adults (LADA) or type 1 diabetes presenting in adulthood. The discriminating features are:

• Young age (34) and lean habitus (BMI 23) — atypical for type 2.
• Significant weight loss (6 kg) and symptomatic hyperglycaemia (polyuria, nocturia) — suggests insulin deficiency, catabolism.
• Family history of type 1 diabetes and autoimmune disease — autoimmune clustering.
• HbA1c 72 mmol/mol with new onset — significant hyperglycaemia. [1]

Investigations (4 marks):

1. Anti-GAD65 antibody — the first-line autoimmune marker for LADA. If positive, LADA is confirmed. Extend the panel with anti-IA2 and zinc transporter-8 (ZnT8) antibodies if GAD65 is negative but suspicion is high.
2. C-peptide level (with concurrent glucose) — assess endogenous insulin production. Low or inappropriately normal C-peptide in the setting of hyperglycaemia indicates beta-cell failure. A preserved C-peptide supports type 2 or MODY.
3. Ketones (beta-hydroxybutyrate) — assess for ketosis/DKA risk. A patient with significant insulin deficiency is at risk of ketoacidosis.
4. Baseline metabolic panel — U&E, venous blood gas (if ketotic), TFTs (screen for coexisting autoimmune thyroid disease). [1]

Classification logic (3 marks): [1]

If anti-GAD65 is positive with low C-peptide — this is LADA (slowly progressive type 1). She will likely require insulin within months to years. The management principle: do not treat LADA with escalating oral hypoglycaemics and re-present in DKA. Early insulin (even basal insulin) preserves residual beta-cell function and prevents ketoacidosis. [1]

If antibodies are negative and C-peptide is preserved — consider MODY (check family history of diabetes across generations, onset under 25; HNF1A-MODY is sulphonylurea-sensitive; GCK-MODY is benign fasting hyperglycaemia). Genetic testing confirms. [1]

If antibodies are negative, C-peptide is preserved, and there is a metabolic syndrome phenotype — type 2 diabetes (unusual given her BMI, but possible in high-risk ethnic groups). [1]

Management implication: The classification directly determines treatment. Mislabelling a LADA patient as type 2 risks ketoacidosis. Mislabelling a MODY patient as type 1 commits them to lifelong unnecessary insulin. The classification question is the first question to answer in any new diabetes diagnosis. [1]