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PA14.1-2 | Microcytic Anemias — A SNAPPS Clinical Reasoning Exercise
CLINICAL SCENARIO
A clinical reasoning assignment using the SNAPPS framework to work through a diagnostically challenging case of microcytic anaemia in a young woman. This case is intentionally designed to reward deep reasoning — a reflex diagnosis of iron-deficiency anaemia will not hold up against the data. Students who engage carefully with the laboratory findings and family context will arrive at a different, more nuanced conclusion.
Instructions
Read the clinical vignette below carefully. Work through each SNAPPS section in order — each section builds on the one before. Use the exact laboratory values provided; do not substitute invented data. Your response must be 1800-2200 words in total across all six sections. Aim for diagnostic precision, not length.
Submit as a single document with each SNAPPS section clearly headed.
Length: 1800-2200 words total across all six sections. Section word targets are guidelines; quality of reasoning matters more than exact word count.
What to Submit
S — Summarise the Case
N — Narrow the Differential
A — Analyse the Differential
P — Probe the Faculty / Probe Yourself
P — Plan Management
S — Select a Topic for Self-Directed Learning
Grading Rubric — Microcytic Anaemia SNAPPS Reasoning Rubric
| Criterion | Points | Full-marks descriptor |
|---|---|---|
| 5 pts | Summary is concise, selective, and diagnostically purposeful. Includes all 6-8 key data points (age, family background, diet, family history of anaemia, CBC values, iron studies) without including irrelevant detail. A colleague reading it could immediately engage with the differential. | |
| 5 pts | All four required differentials listed (IDA, beta-thal trait, ACD, sideroblastic). Each has a specific, case-grounded justification (not generic textbook rationale). Ranking is plausible and reasoned. | |
| 5 pts | Correctly identifies beta-thalassaemia trait as top diagnosis. Explicitly cites Mentzer Index with calculation (63 ÷ 5.8 = 10.86, <13), normal RDW, elevated RBC count, normal ferritin, normal transferrin saturation, and target cells as supporting evidence. For each alternative diagnosis, names the specific lab finding that makes it less likely. | |
| 5 pts | 3-5 specific, answerable questions that reveal genuine uncertainty (e.g., 'Would HPLC show HbA2 ≥3.5% confirming beta-thal trait?', 'Should we test for alpha-thalassaemia given her South Asian background?', 'How do I counsel this patient's mother?'). Each question linked to a specific investigation or information source. | |
| 5 pts | Plan addresses all six required elements: confirmatory HPLC with expected HbA2 result, explicit contraindication of iron supplementation with mechanism (risk of iron overload), patient education/reassurance (trait vs disease distinction), implications of mother's chronic anaemia, Sindhi community high carrier rate and premarital screening, reproductive counselling for future partner. Demonstrates understanding that the clinical action is counselling, not treatment. | |
| 5 pts | Topic selection is specific and directly linked to a named uncertainty from this case (not a generic 'I want to learn more about thalassaemia'). Justification demonstrates metacognition — identifies what the student does not yet know and why it matters. Provides 1-2 actionable references (textbook chapter with section, or peer-reviewed article with title/journal). |