A DIAGNOSTIC-TEST FOR HEPARIN-INDUCED THROMBOCYTOPENIA - DETECTION OFPLATELET MICROPARTICLES USING FLOW-CYTOMETRY

Based on our previous observation that heparin-induced thrombocytopeni a (HIT) sera can generate platelet microparticles from washed platelet s in a heparin-dependent fashion, we developed a test for HIT using fl ow-cytometry to measure heparin-dependent platelet microparticle forma tion. During the developmental phase of the assay the optimal physical conditions for microparticle generation were defined. 133 sera were t hen evaluated using the microparticle assay and the serotonin release assay to determine the threshold for defining a positive result that g ave optimal sensitivity and specificity. The microparticle assay was t hen prospectively evaluated against the serotonin release assay in 202 sera referred to our laboratory for HIT testing. Overall agreement be tween the two assays was 96% (Cohen's kappa = 0.91). When the clinical data were reviewed on patients whose sera gave discrepant results bet ween the two assays, no case of HIT was detected by one assay and miss ed by the other, The platelet microparticle assay is as accurate as th e serotonin release assay and may be a useful non-radioactive test for HIT.