Introduction: The prompt assessment and the reversal of direct oral anticoagulants (DOACs) are urgent matters in the emergency care setting. Thus, we planned to elucidate the adequate prothrombin time (PT) test for the evaluation of the anticoagulant effects of various DOACs. Methods: The anticoagulant effects of rivaroxaban, apixaban, and edoxaban were measured with 3 PT tests (Triniclot PT Excel S, Neoplastin R, and Thromborel S). Human plasma was spiked with each DOAC at a range of 0 to 1000 ng/mL, and the PT was measured using each PT test. In another series, the reversal effect of either 4-factor prothrombin complex concentrate (PCC) or activated PCC (aPCC) was evaluated with each PT test. Results: All PT reagents correlated with the concentrations of each DOAC, however, the reactivity was considerably different between the DOACs and the PT tests. A prolonged PT with DOACs was reversed both by PCC and aPCC in a dose-dependent manner; however, Triniclot PT Excel S showed reprolongation of the PT with a higher dose of PCC. Conclusion: The proper choice of PT test is necessary for the assessments of the anticoagulant activity of DOACs. It is also important to understand the different characteristics of each PT test for the assessment of the reversal effects of PCC.

Clinical demand for the prompt assessment of the activity of direct-acting factor Xa inhibitors in the emergency care setting is increasing. In the present study, we examined whether prothrombin time (PT) tests can serve as a clinically useful indicator of anti-factor Xa activity. In the first series, the in vitro effect of edoxaban on PT was evaluated by spiking human plasma with edoxaban and measuring PT using three different commercial PT tests. In the second series, the reversal effect of prothrombin complex concentrates (PCC) and activated PCC (aPCC) in edoxaban-spiked plasma was evaluated. In the third series, PT of plasma samples from patients administered either 15 or 30 mg/day of edoxaban was assessed, and the results were compared with edoxaban concentrations determined by a calibrated anti-factor Xa activity assay. The spike test revealed that all PT reagents positively correlated with edoxaban. The sensitivity to edoxaban varied among the three reagents and Triniclot(®) Excel S showed the best performance. Prolonged PT by edoxaban was reversed by PCC and aPCC in a dose-dependent manner; however, complete reversal was not achieved. Positive correlation between anti-factor Xa activity and PT was shown in the clinical samples at the edoxaban range from 0 to >300 ng/mL.

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Background The mixing test is used to identify the pathway to follow-up testing and is also useful for the investigation of lupus anticoagulant (LA) positivity. “To completely correct” indicates clotting factor deficiency, while “to not correct” indicates the presence of a clotting factor inhibitor including LA. “Index of circulation anticoagulant” and/or “percent correction” is used to interpret the results of mixing studies, but it does not accurately differentiate factor inhibitors from LA. Aim To precisely differentiate hemophilia A (HA), HA with inhibitor (HA-inh), and LA using the clot waveform analysis (CWA)-based mixing test. Methods Plasma samples from HA, LA, and HA-inh including acquired HA were incubated with normal plasma in 9:1, 1:1, and 1:9 mix ratios. From activated partial thromboplastin time CWA at 0-minute (immediately) and 12-minute incubation, the ratios of CWA parameters at 12 minutes/0 minute (inhibitor index) were assessed. Results The inhibitor index values of CWA parameters obtained using the mixing test in a 1:1 ratio demonstrated a significant difference between HA-inh and LA but could not differentiate LA from HA-inh completely. Plasmas used for the mixing tests in 9:1 and 1:9 ratios were able to fully distinguish between HA-inh (>0.5 BU/mL) and LA. These indices significantly correlated with inhibitor titer below 40 BU/mL (r > 0.90), possibly estimating FVIII inhibitor titer from the inhibitor index. Plasmas in HA and LA could be distinguished by mixing in a 1:1 ratio at 0 minute (immediately). Conclusion The inhibitor index from CWA-based mixing tests with a 12-minute incubation could differentiate among HA, HA-inh, and LA quickly.

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