Predictors of PCSK9 (Proprotein Convertase Subtilisin/Kexin Type 9) Inhibitor Prescriptions for Secondary Prevention of Clinical Atherosclerotic Cardiovascular Disease

Background: Little is known about patterns of PCSK9i (proprotein convertase subtilisin/kexin type 9 inhibitor) use among patients with established clinical atherosclerotic cardiovascular disease. This study's objective was to describe PCSK9i prescribing patterns among patients with atherosclerotic cardiovascular disease. Methods: We used a national outpatient clinic registry linked to zip-code level on household income from the US Census to assess characteristics of patients with atherosclerotic cardiovascular disease and LDL-C (low-density lipoprotein cholesterol) <190 mg/dL between September 1, 2015, and September 30, 2019, who did and did not receive PCSK9i prescriptions and practice-level and temporal variation in PCSK9i prescriptions. We assessed predictors of PCSK9i prescription with a multivariable mixed effects regression model which included patient covariates as fixed effects and the cardiology practice as a random effect. Adjusted practice-level variation in PCSK9i prescribing was evaluated with median odds ratio (OR). Results: Of 2 148 100 patients meeting study inclusion criteria, 27 249 (1.3%) received PCSK9i prescriptions. Receiving a PCSK9i prescription was associated with White race (versus non-White: OR, 1.78 [95% CI, 1.55-1.83]); high estimated household income (versus low income: OR, 1.18 [95% CI, 1.08-1.29]), and urban or suburban (versus rural) practice location (urban: OR, 1.47 [95% CI, 1.32-1.64]; suburban: OR, 1.25 [95% CI, 1.13-1.39]). Hispanics had lower odds of receiving PCSK9i prescriptions (OR, 0.66 [95% CI, 0.57-0.76]). The adjusted median odds ratio was 2.68 (95% CI, 2.46-2.94), consistent with clinically significant practice-level variation in PCSK9i prescriptions. No differences in quarterly PCSK9i prescription rates were observed before and after price reductions for evolocumab and alirocumab initiated during the fourth quarter of 2018 and first quarter of 2019, respectively. Conclusions: This study highlights racial, socioeconomic, geographic, and practice-level variations in early PCSK9i prescriptions which persist despite adjustment for clinical and demographic factors. After adjustment, 2 randomly selected practices would differ in likelihood of PCSK9i prescription by a factor of >2.