Measurement of dabigatran, rivaroxaban and apixaban in samples of plasma, serum and urine, under real life conditions. An international study.

BACKGROUND: The utility of measuring non-vitamin K antagonist oral anticoagulants (NOACs) in plasma, serum and urine samples and with the point-of-care test (POCT) on urine samples should be analysed in an international laboratory study. METHODS: The study was performed to determine the inter-laboratory variance of data from two chromogenic assays each for the NOACs rivaroxaban, apixaban and dabigatran, and to analyse the sensitivity and specificity of the POCT assays for factor Xa- and thrombin inhibitors. Plasma, serum and urine samples were taken from six patients in each group on treatment with a NOAC. RESULTS: The inter-laboratory variances, which can be identified best by the coefficient of variation, ranged from 46% to 59% for apixaban, 63% to 73% for rivaroxaban and 39% to 104% for dabigatran using plasma, serum or urine samples and two chromogenic assays for each NOAC. The concentrations were about 20% higher in serum compared to plasma samples for apixaban and rivaroxaban, and 60% lower for dabigatran. The concentration in urine samples was five-fold (apixaban), 15-fold (rivaroxaban) and 50-fold (dabigatran) higher. Sensitivity and specificity of POCT for apixaban, rivaroxaban, and dabigatran were all >94%. CONCLUSIONS: The inter-laboratory study showed the feasibility of measurement of apixaban, rivaroxaban, and dabigatran in plasma, serum and urine samples of patients on treatment. Dabigatran was determined at far lower levels in serum compared to plasma samples. Concentrations of NOACs in urine were much higher compared to plasma. The POCT was highly sensitive and specific for all three NOACs.

Determination of dabigatran in plasma, serum, and urine samples: comparison of six methods.

BACKGROUND: Assessing the anticoagulant effect of dabigatran may be useful in certain clinical settings. When plasma sampling is not available, serum or urine samples may provide another option for dabigatran determinations. METHODS: Dabigatran was assessed in patients on treatment under real-life conditions in plasma samples by four clotting time-based assays and in plasma, serum, and urine samples by two chromogenic substrate methods. RESULTS: The concentrations of dabigatran in patients' plasma samples were not different for the Hemoclot test (106.8±89.4 ng/mL) and the ecarin clotting time (ECT, 109.5±74.5 ng/mL, p=0.58). Activated partial thromboplastin time and prothrombinase-induced clotting time showed low correlations with the other assays. Chromogenic assays measured similar concentrations as Hemoclot and ECT. For both chromogenic assays, the concentrations of dabigatran were about 70% lower in serum than in plasma samples (p<0.0001). The intra-class coefficient (ICC, Bland-Altman analysis) was strong comparing ECT, Hemoclot thrombin inhibitor (HTI) assay, and the two chromogenic assays (r=0.889-0.737). The ICC was low for comparisons of the chromogenic assays of serum vs. plasma values (ICC, 0.15 and 0.66). The ICC for the determination of dabigatran in urine samples by the two chromogenic assays (5641.6±4319.7 and 4730.0±3770.2 ng/mL) was 0.737. CONCLUSIONS: ECT, HTI, and chromogenic assays can be used to determine dabigatran in plasma samples from patients under real-life conditions. Chromogenic assays require further improvement to reliably measure dabigatran in serum samples. Dabigatran concentrations in urine samples can also be determined quantitatively.

Accuracy of a Rapid Diagnostic Test for the Presence of Direct Oral Factor Xa or Thrombin Inhibitors in Urine-A Multicenter Trial.

The rapid determination of the presence of direct oral anticoagulants (DOACs) in a patient remains a major challenge in emergency medicine and for rapid medical treatment decisions. All DOACs are excreted into urine. A sensitive and specific point-of-care test has been developed to determine whether they are present in patient urine samples. This prospective multicenter study aimed to demonstrate at least 95% correct positive and negative predictive results for factor Xa and thrombin inhibitors in urine samples using DOAC Dipstick pads compared with liquid chromatography-tandem mass spectrometry (LC-MS/MS) (NCT03182829). Nine hundred and fourteen subjects were included and 880 were evaluated per protocol (factor Xa inhibitors apixaban, edoxaban, and rivaroxaban: n = 451, thrombin inhibitor dabigatran: n = 429) at 18 centers. The sensitivity, specificity, accuracy, and predictive values and agreement between methods for determination of factor Xa inhibitors were at least noninferior to 95% with a 0.5% margin and of thrombin inhibitor superior to 97.5%. These results were compared with LC-MS/MS results in the intention-to-analyze cohort (all p < 0.05). The receiver operating curve showed c-values of 0.989 (factor Xa inhibitors) and 0.995 (thrombin inhibitor). Visual evaluation of the factor Xa and thrombin inhibitor pads was not different between centers. Qualitative determination of both types of DOACs was accurate using the DOAC Dipstick compared with using LC-MS/MS. The high predictive values may impact laboratory and clinical decision-making processes.