Investigation for antiphospholipid syndrome after unprovoked venous thromboembolism — SCE Rheumatology MCQ

Correct answer: C — Consider antiphospholipid antibody testing with specialist advice on timing and interpretation, without routine hereditary thrombophilia testing

This is an unprovoked proximal DVT for which anticoagulation is planned to stop. NICE therefore recommends considering antiphospholipid antibody testing because identifying antiphospholipid syndrome could alter the assessment of recurrence risk and long-term anticoagulation. However, anticoagulants can affect thrombophilia assays, particularly clot-based lupus anticoagulant testing, so the timing and interpretation should be agreed with the specialist coagulation laboratory rather than using an unqualified result obtained during apixaban exposure. A incorrectly applies the restriction on hereditary thrombophilia testing to all thrombophilia investigations. NICE distinguishes acquired antiphospholipid antibodies, which should be considered when anticoagulation is to be stopped. B reverses the appropriate priorities: hereditary testing is not routinely indicated here because she has no first-degree relative with VTE, whereas antiphospholipid antibody testing may directly influence the stopping decision. D ignores both the restricted indication for hereditary testing and anticoagulant-related analytical interference. E recognises that apixaban may affect testing, but a prespecified unsupervised 48-hour interruption is not mandated by NICE and may expose the patient to avoidable thrombotic risk. The laboratory may instead advise appropriately timed sampling or another validated strategy according to the assays available and the individual clinical context.

Reference: Venous thromboembolic diseases: diagnosis, management and thrombophilia testing (NG158) — recommendations 1.9.1–1.9.4 (Published 26 March 2020; last updated 2 August 2023) — https://www.nice.org.uk/guidance/ng158/chapter/Recommendations