Coagulation Tests — MFDS Part 1 MCQ

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ModeratePhysiologyCoagulation TestsMFDS Part 1

A patient has a clinically significant isolated factor VIII deficiency. Which routine laboratory test principally assesses the affected coagulation pathway?

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Correct answer: E — Activated partial thromboplastin time (APTT)

The correct answer is **A, activated partial thromboplastin time (APTT)**. APTT assesses the intrinsic pathway, including factors XII, XI, IX and VIII, as well as the common pathway. An isolated clinically significant factor VIII deficiency therefore typically prolongs the APTT while leaving the PT normal. PT assesses the extrinsic and common pathways, with particular sensitivity to factor VII. INR is a standardised value derived from PT rather than a separate intrinsic-pathway test. Bleeding time relates to primary haemostasis and platelet function and is not an assessment of coagulation-factor pathways. Thrombin time evaluates the final conversion of fibrinogen to fibrin and may be prolonged by fibrinogen abnormalities or thrombin inhibitors.

Reference: Northern Lincolnshire and Goole NHS Foundation Trust, Path Links Blood Science User Guide, section 9.4 Coagulation Screening: Activated Partial Thromboplastin Time, Version 7, 2026. https://www.nlg.nhs.uk/wp-content/uploads/2021/10/INT-INS-302-Blood-Sciences-User-Guide-V6-2026.pdf