Anticoagulant activity of apixaban can be estimated by multiple regression analysis

Background Information on apixaban anticoagulant activity is required to prevent major bleeding or thrombosis during its use. Methods We enrolled 194 patients with nonvalvular atrial fibrillation (NVAF) in whom warfarin was replaced with apixaban: 105 (54.1%) received the standard dose of apixaban (5 mg twice daily [BID]; 5 mg group) and 89 (45.9%) received a reduced dose (2.5 mg BID; 2.5 mg group). Multiple regression analysis was performed to predict the prothrombin time of apixaban (PTa) based on factors including age, body weight (BW), serum creatinine, and CHA 2 DS 2 ‐VASc score. Results PTa and PT of warfarin (PTw) were significantly correlated in both groups (correlation coefficient R = 0.239 [ P = .014] in the 5 mg group; R = 0.248 [ P = .019] in the 2.5 mg group). PTa in the 5 mg group was predicted as follows: 16.952‐0.036 × BW +0.299 × CHA 2 DS 2 ‐VASc score ( P < .0004; R = 0.378). However, in the 2.5 mg group, PTa could not be predicted. The mean of the predicted and measured PTa values in the 5 mg group was 15.6 s, which was similar to the mean measured PTa of 15.5 s in the 2.5 mg group. Conclusions PT can be predicted by a formula including simple clinical parameters in patients receiving the standard dose of apixaban. This simple predictive formula may help to stratify bleeding and thrombosis risks in patients treated with apixaban.