Heparinase-modified thrombelastometry: inactivation of heparin in plasma samples.

Background: The heparinase-modified thrombelastometry (HEPTEM) assay is a promising tool to assess the coagulation status of heparinised patients. The aim of our study was to examine the heparin neutralizing capability of the HEPTEM assay in plasma samples. Methods: In the HEPTEM assay, blood or plasma samples become activated via the intrinsic pathway in the presence of a heparin processing enzyme. Results: We examined coagulation times (CTs) in the presence of increasing amounts (0 - 4 IU/mL) of heparin. We found that up to a concentration of 0.5 IU/mL, heparin is completely neutralized. However, CTs increased linearly in the presence of heparin concentrations higher than 0.5 IU/mL, indicating incomplete heparin neutralization in the standard HEPTEM assay. Conclusions: We provide herein a mathematical procedure to correct the misleadingly prolonged CTs (for heparin > 0.5 IU/mL) for the HEPTEM assay performed in plasma samples to allow better estimation of the coagulation status in patients requiring intense anticoagulation (e.g. patients undergoing cardiac surgery). (Clin. Lab. 2010;56:585-589)