Evaluation of various laboratory assays in detection of heparin‐induced thrombocytopenia in an adult general ICU

Summary Introduction Heparin-induced thrombocytopenia (HIT) is an immune-mediated complication of heparin therapy. Our objective was (i) to compare various laboratory assays for HIT against clinical probability (4-T score) and 14C-serotonin release assay (SRA), which was the composite gold standard and (ii) to determine the incidence of HIT in the ICU. Methods The study group (n = 217) consisted of consecutive ICU patients with heparin exposure followed by thrombocytopenia. The clinical probability (4-T score) was applied to the study group. Enzyme-linked immunosorbent assay (ELISA), particle gel immunoassay (PGIA), SRA, and platelet aggregation assay (PAA) were performed. Results The 4-T score showed that 1/217 patients had high probability, 48 had intermediate probability, and 168 had low probability for HIT. One patient was positive by SRA, three by PGIA, and 33 by ELISA. The incidence based on a combination of clinical features and laboratory findings was 1.8%. Conclusions A greater number of false positives were observed by ELISA than by PGIA when compared to a composite gold standard of SRA and clinical probability. The incidence of SRA-positive HIT was 0.46% (1/217).