P2Y12 Inhibitors Refill Gap Predicts Death in Medicare Beneficiaries on Chronic Dialysis

Introduction: Oral P2Y12 inhibitors (P2Y12-I) are commonly used antiplatelet drugs in patients with endstage kidney disease (ESKD) on chronic dialysis. Although gaps in prescription refills are quite common in patients with ESKD, it remains unclear whether P2Y12-I prescription refill patterns are associated with adverse clinical outcomes. Methods: We used the United States Renal Data System (USRDS) registry for patients with ESKD to capture new P2Y12-I prescriptions from 2011 to 2015. The primary exposure was prescription refill patterns and the primary outcome was all-cause death. Results: Among the 31,243 patients with new P2Y12-I prescription, median age was 64 years; 54% were male; and 39% were Caucasian, 37% African American, and 18% Hispanic. We observed 3 P2Y12-I refill patterns as follows: continuous users (45.1%), noncontinuous users (3.6%), and users with >= 30 days refill gap (51.4%). Prescription refill pattern with >= 30 days refill gap (vs. continuous use) was associated with allcause death (adjusted hazard ratio [HR]: 1.18; 95% confidence interval [CI]: 1.13-1.23). Age and race were the most important risk factors associated with prescription refill pattern. African Americans (vs. Caucasians) were more likely to demonstrate >= 30 days refill gap, (adjusted odds ratio [OR]: 1.43; 95% CI: 1.36- 1.51). In addition, younger patients (vs. older) were more likely to demonstrate >= 30 day refill gap (adjusted OR/decade: 0.9; 95% CI: 0.89-0.92). Conclusion: Nonadherence to P2Y12-I prescriptions is quite common, and disproportionately affects minorities. Younger individuals with ESKD are independently associated with a higher risk of death. The odds of having a refill gap are decreasing for older patients who are more compliant than younger patients. Future studies should investigate whether phenotyping subgroups of patients with ESKD based on prescription refill patterns can help in improving adverse clinical outcomes.