• Rationale and Comments

    In patients with suspected heparin-induced thrombocytopenia, use the “4T’s” score to calculate the pretest probability of heparin-induced thrombocytopenia. This scoring system uses the timing and degree of thrombocytopenia, the presence or absence of thrombosis, and the existence of other causes of thrombocytopenia to assess the pretest probability of heparin-induced thrombocytopenia. It can be excluded by a low pretest probability score (4T’s score of 0-3) without the need for laboratory investigation. Do not discontinue heparin or start a non-heparin anticoagulant in these low-risk patients because presumptive treatment often involves an increased risk of bleeding, and because alternative anticoagulants are costly.

    Sponsoring Organizations

    • American Society of Hematology


    • Systematic review


    • Hematologic


    • Watson H, Davidson S, Keeling D. Guidelines on the diagnosis and management of heparin-induced thrombocytopenia: second edition. Br J Haematol. 2012;159(5):528–40.
    • Cuker A, Gimotty PA, Crowther MA, Warkentin TE. Predictive value of the 4Ts scoring system for heparin-induced thrombocytopenia: a systematic review and meta-analysis. Blood. 2012;120:4160–7.