A simple functional assay for heparin-induced thrombocytopenia/thrombosis syndrome using a full blood count analyser

Objective: Heparin-induced thrombocytopenia (HIT) is a complication of heparin use due to development of HIT antibody which activates platelets resulting in a prothrombotic state. Early diagnosis and management is essential to prevent critical ischaemia or even death resulting from uncontrolled thrombosis. A rapid, sensitive and specific functional laboratory diagnostic test, however, is not available in most hospitals. We aimed to develop a simple assay based on the drop in platelet count of normal donor platelet-rich plasma in the presence of HIT antibody and heparin. Materials and methods: Stored HIT positive and negative plasmas were mixed with normal platelet-rich plasma, heparin at different concentrations, or saline. The platelet counts of the mixtures before and after incubation were determined on a routine blood cell counter. Results: The platelet count dropped significantly in the presence of HIT positive plasma and therapeutic concentration of heparin due to platelet aggregation. The platelet counts dropped only slightly in the control tubes, which could be explained by dilution and non-specific clumping. Conclusions: This proof-of-principle finding suggests this simple test, which can be done in any haematology laboratory with a modern blood cell counter, holds great promise as a simple functional test for laboratory diagnosis of HIT. Further work is required to validate the results. Key words: heparin-induced thrombocytopenia, functional assay, platelets NZJ Med Lab Sci 2014; 68: 65-68