Comparison of the ecarin chromogenic assay and different aPTT assays for the measurement of argatroban concentrations in plasma from healthy individuals and from coagulation factor deficient patients

IntroductionThe aim of this study was to assess the usefulness of different aPTT assays and the ecarin chromogenic assay reaction time (ECA) for measurement of argatroban concentration in plasma from healthy persons as well as in different patient subgroups.MethodsWe spiked plasma samples from healthy individuals, patients under oral anticoagulation (OAT) or with liver dysfunction (LD) with increasing argatroban concentrations (0 – 2000 ng/ml) and performed 4 different aPTTs assays and the ECA.ResultsDepending on argatroban concentrations aPTTs increased in a curvilinear fashion; in plasma from healthy individuals means of calculated argatroban concentration at 2-fold aPTT differed extensively depending on the aPTT reagent used (725 ng/ml to 1136 ng/ml) and were even more pronounced in plasma from coagulation factor deficient patients (460 ng/ml in patients with LD vs. 1172 ng/ml in patients with OAT), whereas ECA showed linear argatroban influence and reliable results in all subgroups.ConclusionsBecause of wide differences in aPTT measurements depending on the aPTT reagent used, interindividual variations and different clinical conditions the aPTT is not the method of choice for monitoring argatroban and the ECA should be preferred.