Off-Label Dosing of Direct Oral Anticoagulants Among Inpatients with Atrial Fibrillation

Introduction Among patients hospitalized for atrial fibrillation (AF), the frequency of off-label direct oral anticoagulant (DOAC) dosing, associated factors, hospital-level variation, and temporal trends in contemporary clinical practice are unknown. Methods Using the Get With The Guidelines ® Atrial Fibrillation (GWTG-AF) registry, patients admitted from January 1 st , 2014 to March 31 st , 2020, and discharged on DOAC therapy were stratified according to receipt of underdosing, overdosing, or recommended dosing. Factors associated with off-label dosing were identified using logistic regression. Hospital-level variation and temporal trends were assessed. Results Of 22,470 patients prescribed a DOAC at discharge from hospitalization for AF (66% apixaban, 29% rivaroxaban, 5% dabigatran), underdosing occurred among 2006 (8.9%), overdosing among 511 (2.3%), and recommended dosing among 19953 (88.8%). Patient-related factors associated with off-label DOAC use included age (underdosing: OR 1.06 per 1-year increase [95% CI 1.06-1.07] and overdosing: OR 1.07 per 1-year increase [1.06-1.09]), dialysis dependence (underdosing: OR 5.50 [3.76-8.05] and overdosing: OR 5.47 [2.74-10.88]), female sex (overdosing: OR 0.79 [0.63-0.99]) and weight (overdosing: OR 0.96 per 1-Kg increase [0.95-1.00]). Across hospitals, the adjusted median odds ratio for off-label DOAC use was 1.45 [95% CI 1.34-1.65] (underdosing: 1.52 [1.39-1.76] and overdosing: 1.32 [1.20-1.84]), indicating significant hospital-level variation. Hospital characteristics associated with underdosing included West vs. Northeast location (OR: 1.55 [1.04-2.31]), rural vs. urban setting (OR: 0.48 [0.28-0.83]), and number of beds (<200 vs. 500+, OR: 1.95 [1.29-2.95]). Recommended dosing significantly increased over time (81.9% in 2014 to 90.9% in 2020, p<0.0001 for trend) with a corresponding decline in underdosing (14.4% in 2014 to 6.6% in 2020, p<0.0001 for trend) and overdosing (3.8% in 2014 to 2.5% in 2020, p=0.001 for trend). Conclusion One of 10 patients hospitalized for atrial fibrillation is discharged on off-label dosing of DOAC with significant variation across hospitals. While the proportion of patients receiving recommended dosing has significantly improved over time, opportunities to improve DOAC dosing persist.