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, hereto termed 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 (CANHEART) cohort, a population-based cohort of almost all adult residents of Ontario, Canada, followed between 2008 and 2012. For each clinical volume quintile, we compared cholesterol testing and major adverse cardiovascular events, defined as time to first event of cardiovascular death, non-fatal myocardial infarction, or non-fatal stroke.

Results — The 10,037 PCPs evaluated had an annualized median volume 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% among the lowest clinical volume quintile physicians to 86% among 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 physicians had the highest rate of major adverse cardiovascular outcomes, compared with the highest quintile volume 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.