Moderate Haemophilia A Diagnosis — ORE Part 1 MCQ

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ModerateHuman Disease & Dental ManagementModerate Haemophilia A DiagnosisORE Part 1

A patient with a hereditary bleeding disorder presents with a prolonged APPT and a normal PT/INR. Factor assay shows factor VIII activity of 3% (normal >50%). What is the diagnosis?

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Correct answer: C — Moderate haemophilia A (factor VIII deficiency)

The combination of prolonged APPT with normal PT specifically indicates intrinsic pathway deficiency. A direct factor VIII assay at 3% activity (normal >50%) confirms factor VIII deficiency. Factor VIII 3% falls within the moderate severity category (1–5%). Option A is excluded because the assay measures factor VIII, not factor IX. Option B (vWD type 3) is excluded because it manifests as secondary factor VIII deficiency due to vWF loss, not a primary factor VIII synthesis defect at 3%. Option D (factor VII) is incorrect because factor VII deficiency causes prolonged PT with normal APPT—the opposite pattern. Option E (warfarin) is excluded because the PT is normal, which would be prolonged if warfarin were active. This is a UK-common diagnosis requiring specialist haemophilia centre management.

Reference: UK Haemophilia Centre Doctors' Organisation; Newcastle Hospitals Laboratories Factor VIII Assay guidance; Sheffield Children's NHS Trust Haemostasis and Thrombosis Guidelines; HEE Genomics Education Haemophilia A resource (2019–2025), https://laboratories.newcastle-hospitals.nhs.uk/test-directory/factor-viii-assay/