Isolated Prolonged APTT — FRCA Final MCQ

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HardPreoperative AssessmentIsolated Prolonged APTTFRCA Final

A 48-year-old man (ASA II, 85 kg) presents for a laparoscopic anterior resection. His pre-operative bloods show an isolated prolonged APTT of 52 seconds (normal 24-38) with normal PT and platelet count. He has no history of bleeding. What is the most likely cause?

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Correct answer: C — Lupus anticoagulant

An isolated prolonged APTT with normal PT and no bleeding history most commonly indicates a lupus anticoagulant (antiphospholipid antibody). Paradoxically, despite prolonging the APTT in vitro, lupus anticoagulant is associated with thrombosis, not bleeding. It is confirmed by a mixing study (APTT does not correct with mixing) and specific confirmatory tests. This patient does NOT need treatment to 'correct' the APTT before surgery. Factor VIII deficiency (haemophilia A) would cause bleeding symptoms. Factor V Leiden prolongs neither PT nor APTT.

Reference: BSH – 2020 – Investigation of prolonged APTT; RCOA – 2023 – Preoperative haematology