Variability in Nonvitamin K Oral Anticoagulant Dose Eligibility and Adjustment According to Renal Formulae and Clinical Outcomes in Patients With Atrial Fibrillation With and Without Chronic Kidney Disease: Insights From ORBIT‐AF II

BACKGROUND: Nonvitamin K oral anticoagulants require dose adjustment based on kidney function.The most common estimate of kidney function employed in clinical practice is estimated glomerular filtration rate (eGFR); however, product monographs recommend the use of the Cockcroft‐Gault estimated creatinine clearance (eCrCl) for dose adjustment. METHODS AND RESULTS: The authors included patients enrolled in the ORBIT‐AF II (Outcomes Registry for Better Informed Treatment of Atrial Fibrillation AF II) trial. Dosing was considered inappropriate when use of eGFR resulted in a lower (undertreatment) or higher (overtreatment) dose than that recommended by the eCrCl. The primary outcome of major adverse cardiovascular and neurological events was a composite of cardiovascular death, stroke or systemic embolism, new‐onset heart failure, and myocardial infarction. Among 8727 in the overall cohort, agreement between eCrCl and eGFR was observed in 93.5% to 93.8% of patients. Among 2184 patients with chronic kidney disease (CKD), the agreement between eCrCl and eGFR was 79.9% to 80.7%. Dosing misclassification was more frequent in the CKD population (41.9% of rivaroxaban users, 5.7% of dabigatran users, and 4.6% apixaban users). At 1 year, undertreated patients in the CKD group had significantly greater major adverse cardiovascular and neurological events (adjusted hazard ratio, 2.93 [95% CI, 1.08–7.92]) compared with the group with appropriate nonvitamin K oral anticoagulants dosing (P=0.03). CONCLUSIONS: The prevalence of misclassification of nonvitamin K oral anticoagulants dosing was high when using eGFR, particularly among patients with CKD. Among patients with CKD, potential undertreatment due to inappropriate and off‐label renal formulae may result in worse clinical outcomes. These findings highlight the importance of using eCrCl, and not eGFR, for dose adjustment in all patients with AF receiving nonvitamin K oral anticoagulants.