PB1096 - Clot Time Ratio (CTR) in atrial fibrillation patients on rivaroxaban

Background: There are clinical situations where information about the anticoagulant effects of rivaroxaban could be useful. Methods for measuring rivaroxaban concentrations are not available at all medical laboratories while the test MRX PT DOAC for measuring the functional effects of rivaroxaban, in CTR (Clot Time Ratio), can be available around the clock.

Aims: To investigate CTR in through and peak samples during rivaroxaban treatment and to correlate the findings to bleeding episodes.

Methods: 3 through- and 3 peak samples previously collected and investigated ([1]) from 60 patients (30 on 20 mg daily and 30 on 15 mg daily) were analysed with MRX PT DOAC. Patients had been followed for 20 months and bleeding and thrombotic events were documented. Non-parametric t-test was used for statistical analyses, when not otherwise specified (Sigma Plot 14.0).
1. Miklic, M., et al. Eur J Clin Pharmacol, 2019. 75(8): p. 1069-1075.

Results: 178/180 through and 177/180 peak samples were available. Through CTR varied between 0.93-3.36 with median at 1.33 while peak CTR varied between 1.8-7.03 with median at 3.56 (p < 0.001). 28 patients (13 on 20 mg and 15 on 15 mg) had suffered bleeding. Peak CTR ranged between 1.89-6.20 for patients on 20 mg and patients with bleeding(s) had higher mean-CTR than patients without bleeding (p=0.038, Student’s t-test). Patients on the adjusted, lower dose of 15 mg had similar peak CTR ranging between 1.80-7.03 but there was no significant difference in mean-CTR between patients with or without bleeding(s) (p=0.678).

Conclusion(s): Clot time ratio (CTR) at peak was higher at group level (p < 0.05) in patients on 20 mg rivaroxaban who suffered from bleeding compared to patients who didn't. However, the difference found at the level of individual patients in the present study was not sufficient to clinically distinguish the patients at risk of bleeding and might warrant further, larger studies.