BACKGROUND: Guideline-adherent oral anticoagulant (OAC) treatment in atrial fibrillation (AF) remains a challenge. In Denmark, most patients with AF are treated in general practice. Nevertheless, determinants of OAC prescription in primary care are poorly understood.

AIM: To investigate variation in OAC treatment adherence between general practice clinics and to identify clinic characteristics associated with a lower propensity to prescribe OAC treatment.

DESIGN & SETTING: Nationwide register-based cohort study including prevalent and incident patients with AF and CHA₂DS₂-VASc score ≥2 (n = 165 731) listed with Danish general practice clinics (n = 1666) in 2021.

METHOD: The main outcome was OAC treatment adherence assessed as proportion of days covered (PDC). We used clinic OAC propensity to evaluate variation. OAC propensity was quantified as ratios between observed and expected adherence. Expected adherence was estimated based on the composition of the clinic patient populations. Sampled reference populations were constructed to account for random variation. Linear regression models examined associations between OAC propensity and clinic characteristics.

RESULTS: The PDC with OAC treatment in the AF population was 78%. OAC propensity in clinics in the 90^th percentile was 20% higher compared with clinics in the 10^th percentile; however, this difference was reduced to 3% when accounting for random variation. Modest associations were observed between clinic characteristics and OAC propensity. The most significant difference was in the correlation between geographic location and OAC propensity, showing an 8% gap between top and bottom-performing regions.

CONCLUSION: The study suggests persistent underutilisation of OAC treatment in patients with AF and little variation in OAC prescription patterns across general practice clinics.