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

 

Ref:

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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