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Coagulation Disorders — NDEB AFK MCQ

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ModerateBiomedical SciencesCoagulation DisordersNDEB AFK

A patient's blood results show a prolonged activated partial thromboplastin time (aPTT) with a normal prothrombin time (PT). Which factor deficiency is most likely?

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Correct answer: B — Factor VIII

aPTT measures the intrinsic pathway (factors XII, XI, IX, VIII). PT measures the extrinsic pathway (factor VII) and common pathway (X, V, II, fibrinogen). An isolated prolonged aPTT with normal PT indicates a deficiency in the intrinsic pathway, most commonly factor VIII (haemophilia A) or factor IX (haemophilia B). Factor VII deficiency would prolong only the PT.

Reference: Hoffbrand – Postgraduate Haematology, 7th ed., 2016