Heparin-Induced Thrombocytopenia vs Antiphospholipid Syndrome
Heparin-Induced Thrombocytopenia and Antiphospholipid Syndrome are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.
Heparin-Induced Thrombocytopenia vs Antiphospholipid Syndrome at a glance
- Heparin-Induced Thrombocytopenia: Antibody-mediated platelet activation by heparin-PF4 complexes causing paradoxical thrombosis with thrombocytopenia.
- Antiphospholipid Syndrome: Autoimmune disorder with antiphospholipid antibodies causing arterial/venous thrombosis and pregnancy morbidity.
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Side-by-side comparison
| Feature | Heparin-Induced Thrombocytopenia | Antiphospholipid Syndrome |
|---|---|---|
| At a glance | Antibody-mediated platelet activation by heparin-PF4 complexes causing paradoxical thrombosis with thrombocytopenia. | Autoimmune disorder with antiphospholipid antibodies causing arterial/venous thrombosis and pregnancy morbidity. |
| Classic presentation | Platelet count fall 5-10 days after starting heparin with new thrombosis — the 'paradoxical' picture of thrombocytopenia with clotting rather than bleeding.; Often asymptomatic platelet drop noticed on routine CBC 5-10 days after starting heparin; Rapid-onset HIT (within hours) in patients with heparin exposure within prior 100 days;… | Triad in catastrophic APS: rapidly progressive multi-organ thrombosis (≥3 organs), histologic confirmation of small vessel occlusion, and persistent APL antibodies.; DVT, PE — most common manifestation; Arterial thrombosis — stroke (especially in young patients), TIA, MI, limb ischemia; Recurrent pregnancy loss (≥3 consecutive losses… |
| Workup / key labs | 4Ts score 0-3 (low) → HIT unlikely; 4-5 (intermediate) and 6-8 (high) → stop heparin, start non-heparin anticoagulant, send PF4 ELISA and confirmatory functional assay. Diagnosis = clinical probability + positive functional assay.; Calculate 4Ts score: Thrombocytopenia, Timing, Thrombosis, oTher causes (each 0-2 points);… | Revised Sapporo (Sydney) criteria — requires ≥1 clinical criterion (vascular thrombosis or pregnancy morbidity) AND ≥1 laboratory criterion (LA, anti-cardiolipin, or anti-β2GP1) on two occasions at least 12 weeks apart. The 2023 ACR/EULAR criteria add weighted domain scoring and emphasize triple positivity.; Three core antiphospholipid… |
| Imaging | Lower extremity venous duplex Doppler in all patients diagnosed with HIT; CT/CTA or other vascular imaging guided by clinical signs of thrombosis; CT abdomen if adrenal hemorrhage suspected | Duplex US, CTPA, MRI brain as clinically indicated by symptoms; Echocardiogram to evaluate for Libman-Sacks endocarditis |
| First-line treatment | STOP all heparin immediately (including flushes, LMWH, heparin-coated catheters); Start non-heparin anticoagulant at therapeutic dose — argatroban (direct thrombin inhibitor, hepatic clearance) or bivalirudin (DTI, predominantly enzymatic/proteolytic clearance with minor renal component) for inpatients; fondaparinux acceptable for… | Acute thrombosis — therapeutic anticoagulation: unfractionated heparin or LMWH bridge to warfarin (INR 2-3); Long-term venous thrombosis — warfarin INR 2-3 indefinitely; Long-term arterial thrombosis or recurrent venous thrombosis on warfarin — warfarin INR 3-4, or warfarin + low-dose aspirin; DOACs (rivaroxaban, apixaban) are INFERIOR… |
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