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Biotin assay interference — SCE Endocrinology MCQ

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ModerateThyroidBiotin assay interferenceSCE Endocrinology

A 25-year-old woman presents with palpitations. TSH is 0.18 mU/L and free T4 is 14 pmol/L. She is clinically well and takes biotin supplements for hair loss. What is the most appropriate next step?

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Correct answer: A — Repeat thyroid function tests after withholding biotin

Biotin can interfere with immunoassays and produce misleading thyroid results. Repeating tests after withholding biotin is appropriate before diagnosing thyroid disease. Treating a clinically well patient on one potentially artefactual result risks harm.

Reference: NICE NG145; Association for Clinical Biochemistry Guidance