LABORATORY MONITORING OF THROMBOPROPHYLAXIS WITH LOW-MOLECULAR-WEIGHT AND STANDARD HEPARIN

This study was made to evaluate assays for monitoring of low dose heparin thromboprophylaxis and to evaluate its efficacy in reduction of hypercoagulation. Patients with medical diseases scheduled for routine thromboprophylaxis were subcutaneously treated with either 5.000 anti XaU low molecular weight (LMW) heparin once daily (n=20) or 5.000 IU standard (ST) heparin 3 times daily (n= 19). On days 1,2,3, before, 1 and 4 hours after heparin injection APTT, TCT, anti Xa, Heptest, thrombin-antithrombin complexes (TAT), and D-Dimer levels were measured. In the LMW heparin group, median values of APTT and TCT slightly increased after heparin and the ranges of pre- and postinjection values showed extensive overlap. However, values of anti Xa and Heptest markedly increased, showing complete separation of ranges. In the ST heparin group neither APTT, TCT, anti Xa, nor Heptest were significantly different comparing pre- and post-heparin values. Half of the patients in both groups had subclinical hypercoagulation at baseline (TAT>5ng/ml, D-Dimer>200ng/ml). on day 3 of prophylaxis this percentage was not significantly decreased. Moreover, several patients in both groups increased in TAT and D-Dimer. In the LMW heparin group, negative correlations between body weight and 4 h postinjection heparin levels were found (anti Xa R=-0.50, Heptest R=-0.31) and between 1 h post-injection heparin and TAT and D-Dimer levels 3 h later (TAT-anti Xa R=-0.58, TAT-Heptest R=-0.64, D-Dimer-anti Xa R=-0.32, D-Dimer-Heptest R=-0.33). These results show that low dose LMW but not ST heparin therapy can be monitored by the anti Xa test or the Heptest.