Estimating the Pretest Probability of HIT: The «Four T's»

Additional Information

Score Description

The "Four T's" is a pretest clinical score for heparin-induced thrombocytopenia (HIT), that quantifies the clinical findings associated with HIT. Published in 2006, the score was prospectively applied in 100 patients at a single center (Hamilton General Hospital, Canada) and in 236 patients across multiple centers in Germany and Austria. In all centers, a low-risk clinical score had a high negative predictive value for the detection of HIT antibodies. Any changes in clinical findings (development of new thrombosis, further drop in platelet count) should prompt reevaluation and recalculation of the score.

Further Reading

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 Apr;4(4):759-65.