skip to main content

CDI Testing Interpretation — Medical Practice MCQ

Instant feedback + full explanation. One question, done properly.

HardInfectious DiseasesCDI Testing Interpretation

A formed stool is mistakenly submitted from a patient with one bowel motion daily. NAAT detects toxigenic C. difficile but toxin EIA is negative; there is no colitis syndrome. What is the best interpretation?

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

Reveal the answer and explanation

Correct answer: A — Colonisation is more likely; do not diagnose or treat CDI without compatible diarrhoea and reassess other causes

The best answer is “Colonisation is more likely; do not diagnose or treat CDI without compatible diarrhoea and reassess other causes”. CDI is a clinical syndrome, not a NAAT result alone. A formed stool from a patient without diarrhoea should not be tested, and NAAT may detect colonisation. In the absence of compatible symptoms, avoid treatment and reassess other explanations; toxin negativity further fails to support active toxin-mediated colitis.

Reference: NICE NG199 C. difficile antimicrobial prescribing: https://www.nice.org.uk/guidance/ng199/chapter/Recommendations