4Ts Score for Heparin-Induced Thrombocytopenia
Estimates the pre-test probability of heparin-induced thrombocytopenia (HIT) using 4 clinical criteria. Low score safely excludes HIT; intermediate/high requires laboratory confirmation.
Score interpretation
4Ts Score 0–3: Low pre-test probability for HIT (~1%). Negative predictive value >99%.
→ HIT very unlikely. No need for HIT antibody testing in most cases. Continue heparin if clinically indicated. Investigate other causes of thrombocytopenia (sepsis, drug-induced, TTP, bone marrow suppression).
4Ts Score 4–5: Intermediate pre-test probability (~14%). HIT antibody testing required.
→ Stop all heparin (UFH and LMWH). Send anti-PF4/heparin ELISA and functional assay (SRA/HIPA) urgently. Start alternative anticoagulation: argatroban or fondaparinux. Do NOT start warfarin until platelets recovered. Haematology review.
4Ts Score 6–8: High pre-test probability (~50%). HIT likely.
→ Stop ALL heparin immediately (including line flushes and heparin-coated catheters). Start therapeutic-dose alternative anticoagulation (argatroban IV or fondaparinux). Send HIT antibodies urgently. Haematology consultation. Screen for thrombosis (limb USS, CT PE if indicated). Do NOT transfuse platelets.
Interpretation bands for the 4Ts Score. Apply clinical judgement and local guidance.
References
- Lo GK, et al. Evaluation of pretest clinical score (4 T's) for the diagnosis of heparin-induced thrombocytopenia in two clinical settings. J Thromb Haemost. 2006;4(4):759–765.
- Cuker A, et al. American Society of Hematology 2018 guidelines for management of venous thromboembolism: heparin-induced thrombocytopenia. Blood Adv. 2018;2(22):3360–3392.
Related
Curated clinical cross-links plus same-class fallbacks.
- Protamine Sulphate · Heparin Reversal Agent
- Unfractionated Heparin (ACS / PCI) · Anticoagulant / ACS / PCI
- Bivalirudin (PCI Anticoagulation) · Direct Thrombin Inhibitor / PCI
- Protamine Sulphate (Heparin Reversal) · Heparin Reversal / Cardiac Surgery
- Heparinoid · Topical heparin analogue
- Unfractionated Heparin (IV) · Anticoagulant — ACS / PE / Thrombus
- Major Haemorrhage / Massive Transfusion · BCSH; RCOA; RCEM; RCS — BCSH Guidelines
- Anaemia Investigation · BSH / NICE
- Splenomegaly Workup · BSH; BMJ Best Practice
- Deep Vein Thrombosis Diagnosis and Treatment · NICE CG144 / NICE NG158
- Sickle Cell Crisis · BSH 2021 / BCSH
- Neutropenic Sepsis · NICE CG151 2012 / ESMO
Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.