Evaluation of clinical and laboratory data for early diagnosis of heparin-induced thrombocytopenia

PURPOSE.Results of a study to determine the utility of combining laboratory values and clinical probability scores to improve the detection of heparin-induced thrombocytopenia (HIT) are reported. METHODS.In a retrospective, single-site, chart review-based investigation, 156 cases in which patients with suspected HIT had positive results on a widely used diagnostic test (the anti-heparin/platelet factor 4, or anti-PF4, assay) were identified; in all cases, the blood specimens had been sent to a reference laboratory for confirmation of HIT via serotonin release assay (SRA). After investigator scoring of the clinical probability of HIT in each case by the 4Tʼs method, a multiple logistic regression model was used to evaluate the combined effect of 4Tʼs scores and anti-PF4 assay values in predicting SRA results. RESULTS.4Tʼs scores indicating an intermediate or high probability of HIT combined with high anti-PF4 test values (i.e., optical density [OD] value of ≥1.4) were strongly predictive of a positive SRA result, as were high-probability 4Tʼs scores alone. Low-probability 4Tʼs scores alone or in combination with anti-PF4 OD values of