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Heparin-Induced Thrombocytopaenia — RACP Adult Medicine MCQ

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ModerateHaematologyHeparin-Induced ThrombocytopaeniaRACP Adult Medicine

A 45-year-old woman undergoing treatment for breast cancer develops sudden onset left leg swelling. Doppler ultrasound confirms a proximal DVT. She has a platelet count of 65 × 10⁹/L (baseline 180). She has been on unfractionated heparin for 7 days post-surgery. Her 4Ts score is 7. What is the most likely diagnosis and next step?

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Correct answer: C — Heparin-induced thrombocytopaenia – cease heparin and commence argatroban

A 4Ts score of 7 indicates high probability of HIT (heparin-induced thrombocytopaenia type II). HIT is an antibody-mediated prothrombotic condition presenting with thrombocytopaenia (typically 30–50% drop) and thrombosis 5–14 days after heparin exposure. ALL heparin must be immediately ceased (including flushes) and a non-heparin anticoagulant commenced (argatroban IV, or fondaparinux SC). Anti-PF4/heparin antibody testing (ELISA) confirms the diagnosis. Warfarin must NOT be started until platelets recover.

Reference: eTG – 2025 – Haematology; ASH – 2018 – HIT Guidelines