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Heparinase-Modified Thrombelastometry: Inactivation of Heparin in Plasma Samples by Gerhard Cvirn, Erwin Tafeit, Gerd Hoerl, Michaela Janschitz, Thomas Wagner, Guenther Juergens, Martin Koestenberger

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).

DOI: Clin. Lab. 2010;56:585-589