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Iron Deficiency Anemia — ABIM Board MCQ

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ModerateGastrointestinal Evaluation of Iron Deficiency AnemiaIron Deficiency AnemiaABIM Board

A 59-year-old man with iron deficiency anemia has a serum ferritin of 12 ng/mL. Colonoscopy 2 years ago was negative. According to current US specialty society guidelines, which ferritin threshold is recommended to diagnose iron deficiency anemia?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: A — Ferritin <45 ng/mL provides optimal sensitivity and specificity

The correct answer is A. The American Gastroenterological Association recommends using a serum ferritin cutoff of <45 ng/mL to define iron deficiency anemia, as it improves sensitivity (85%) while maintaining high specificity (92%) compared to the older threshold of <15 ng/mL, which is less sensitive (59%) despite nearly 99% specificity. Ferritin values like <10 or <5 ng/mL are overly restrictive and not aligned with current US practice. Ferritin remains the most useful single test for iron deficiency; while transferrin saturation is complementary (especially in inflammation), it does not replace ferritin in initial diagnosis.

Reference: American Gastroenterological Association guideline on GI evaluation of iron deficiency anemia (AGA, 2026), Technical review detailing ferritin cutoff performance (AGA Technical Review, 2016)