Heparin platelet factor 4 antibody test for heparin induced thrombocytopenia- a new procedure


Submitted by Pradeep K. Bhagat, MD, Interim Chairman, Department of Pathology


Effective October 4, each time a heparin PF4 antibody test is ordered in the Smart Chart, a 4T’s score calculator prompt will appear. This module must be completed prior to signing lab order and the computed score will characterize the patient as low-, intermediate-, or high risk for having HIT and recommendation will be included based on risk.


Heparin PF4 antibody test has relatively high sensitivity but very low specificity with only 1-2% real positive test. Heparin PF4 should be limited to patients with an intermediate or high pre-test probability of HIT as per the 4T’s score. Inappropriate heparin PF4 antibody testing in patients with low pre-test probability of actually having HIT can result in increased patient care cost and improve specificity of lab testing.


The 4 T’s score is a pre-test clinical scoring system widely used in clinical practice due to limitations of HIT screening test. The 4t’s scoring system incorporates 4 typical features of HIT: (1) Magnitude of thrombocytopenia (2) timing of thrombocytopenia with respect to heparin exposure (3) Thrombosis or other sequelae (4) likelihood of other cause of thrombocytopeniaRef



Cuker, et al., Predictive value of the 4Ts scoring system for heparin-induced thrombocytopenia: a systematic review and meta-analysis. Blood 2012;120:4160


If you have any questions, please call Dr. Bhagat at 484.476.3521.

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