CHA2DS2-VASc and HAS-BLED scores and activated partial thromboplastin time for prediction of high plasma concentration of dabigatran at trough

Abstract

Introduction: Although dabigatran, an oral direct thrombin inhibitor, does not require routine monitoring, high plasma concentration of dabigatran (PDC) at trough level is shown to be a high risk for bleeding in patients with nonvalvular atrial fibrillation (NVAF). As dabigatran prolongs the activated partial thromboplastin time (APTT), we examined relationships of PDC at trough with APTT and clinical features to identify patients at high risk for major bleeding during dabigatran treatment.

Materials and methods: In the consecutive 48 patients with NVAF taking dabigatran at a daily dose of 220mg (n=32) or 300mg (n=16), we measured PDC using HEMOCLOT Thrombin Inhibitor assay and APTT ratio to control before (trough) and 2hours after taking dabigatran.

Results: PDC was positively correlated with APTT ratio (R(2)=0.64, p<0.0001). Using this regression equation and values of median trough PDC 116 (46.7-269) ng/mL observed in patients with major bleeding in the RE-LY trial, we calculated the expected value of APTT ratio corresponding to the 10th percentile of trough PDC (46.7). It was 1.20. There was a significant increase in trough PDC with increasing CHA2DS2-VASc score (p=0.01) and with increasing HAS-BLED score (p=0.01), especially in CHA2DS2-VASc score ≥4 and in HAS-BLED score ≥3, respectively. The highest trough PDC was obtained in patient group with CHA2DS2-VASc score ≥4, HAS-BLED score ≥3, or creatinine clearance ≤80, each combined with trough APTT ratio ≥1.20.

Conclusions: This study provides an important clinical implication for identifying patients at high risk for major bleeding during dabigatran treatment in clinical practice.

Keywords: Activated partial thromboplastin time; CHA(2)DS(2)-VASc score; Dabigatran; HAS-BLED score.