The effect of physician panel size on health care outcomes.

An inadequate supply of primary care providers is leading to a crisis in access. Pressures are being placed on primary care practices to increase panel sizes. The impact of these pressures on clinical processes, patient satisfaction and waiting times is largely unknown, although evidence from recent literature shows that longer waiting time results in higher mortality rates and other adverse outcomes. FY2004, Department of Veterans Affairs primary care patient data are used. GLIMMIX and other generalized linear model models illustrate how expanded panel sizes are correlated with clinical process indicators, patient satisfaction and waiting times, controlling for practice, provider and patient characteristics. We generally find that larger panel sizes are related to statistically significant increases in waiting time. However, larger panel sizes appear to have generally small effects on patient process indicators and satisfaction. Panels with more support staff have lower waiting times and small, improved outcomes. We find panels with older and clinically riskier patients have, on average, slightly lower waiting times and increased likelihoods of positive outcomes than panels with younger, healthier veterans. Female veterans appear to have reduced likelihoods of positive outcomes. Higher priority and female veterans also have lower satisfaction. Further study is needed to analyse the impact of potential panel size endogeneity in this system.