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Root cause analysis — USMLE Step 3 MCQ

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HardEthics, Patient Safety, Quality Improvement, Systems-Based PracticeRoot cause analysisUSMLE Step 3

Before introducing a smart-pump drug library, a safety team performs FMEA and scores each potential failure mode from 1 to 10 for severity, occurrence, and difficulty of detection. Using the conventional product of the three scores to prioritize the first redesign target, which failure mode ranks highest?

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Correct answer: C — Wrong concentration selected: severity 10, occurrence 4, detection difficulty 7

The best answer is “Wrong concentration selected: severity 10, occurrence 4, detection difficulty 7”. Its priority product is 280, exceeding 225, 192, 216, and 192 for the other failure modes. FMEA is prospective: it maps the process and uses severity, probability, and detectability to focus preventive redesign before harm occurs; the score prioritizes investigation rather than proving causation.

Reference: AHRQ PSNet Glossary: Failure Mode and Effects Analysis: https://psnet.ahrq.gov/glossary/failure-mode-and-effect-analysis-fmea