Exploring the effect of factor Xa inhibitors on rotational thromboelastometry: a case series of bleeding patients.

Direct oral anticoagulants (DOACs) have become the standard for thromboembolic risk management. In cases of major bleeding, trauma, or urgent surgery, accurate monitoring of DOAC activity is desirable; however, there is often no rapid, readily available test. We therefore explored the degree to which DOAC activity correlated with two coagulation assays: rotational thromboelastometry (ROTEM) and a standard coagulation assay in bleeding patients. We conducted a retrospective review of patients who experienced bleeding while on DOAC therapy from 2015 to 2017 at a Level 1 trauma center. ROTEM (EXTEM-clotting time {CT} in seconds), activated partial thromboplastin time (aPTT) (in seconds), prothrombin time (PT) (in seconds), DOAC specific drug test (anti-Xa and Hemoclot in ng/mL), and relevant clinical parameters were recorded. Descriptive statistics (median, range) and Spearman correlation coefficients were estimated. Differences between correlations were tested using Williams' t test. Twelve cases were reviewed (13 separate bleeding episodes). Sixteen measurements of DOAC activity, EXTEM-CT, and PT were obtained. The correlations with rivaroxaban activity were 0.96 and 0.86 (p = 0.2062) for PT and EXTEM-CT, respectively. The correlations with apixaban activity were 0.63 and 0.56 (p = 0.7175) for PT and EXTEM-CT, respectively. Analyses were not conducted for dabigatran due to limited data. Although not statistically significant, PT appears to have a higher correlation with direct Xa inhibitor activity than EXTEM-CT. Further research with larger samples is necessary to clarify the differences between ROTEM and standard assays in detecting DOAC activity.