Primary Care Clinical Volumes, Cholesterol Testing, and Cardiovascular Outcomes

Background: It is unknown whether the annual number of primary care physician (PCP) unique outpatient assessments, which we refer to as clinical volume, translates into better cardiovascular preventive care. We examined the relationship between PCP outpatient clinical volumes and cholesterol testing and major adverse cardiovascular event rates among guideline-recommended eligible patients. Methods: This was a retrospective cohort study conducted as part of the Cardiovascular Health in Ambulatory Care Research Team (CAN -HEART) cohort, a population-based cohort of almost all adult residents of Ontario, Canada, followed from 2008 to 2012. For each clinical volume quintile, we compared cholesterol testing and major adverse cardiovascular events, defined as time to first event of cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke. Results: The 10,037 PCPs evaluated had an annualized median vol-ume of 2303 clinical encounters (IQR 1292-3680). Among 4,740,380 patients, 84% underwent guideline-concordant cholesterol testing at least once over 5 years, ranging from 73% with the lowest clinical volume quintile physicians to 86% with the highest. After multivariable adjustment, there was a 10.5% relative increase in the probability of cholesterol testing for every doubling of clinical volumes (95% CI 9.7-11.4; P < 0.001). Patients treated by the lowest volume quintile physicians had the highest rate of major adverse cardiovascular outcomes (compared with the highest volume quintile physicians: adjusted HR 1.15, 95% CI 1.10-1.21; P < 0.001). Conclusions: Patients of physicians with the lowest clinical volumes received less frequent cholesterol testing and had the highest rate of incident cardiovascular events. Further research investigating the drivers of this relationship is warranted.