Primary care quality and cost for privately insured patients in and out of US Health Systems: Evidence from four states

1 | INTRODUCTION Health systems are playing an increasingly important role in health care delivery in the United States. In the past decade, a large number of mergers and acquisitions [...]
Objective: To characterize physician health system membership in four states between 2012 and 2016 and to compare primary care quality and cost between in-system providers and non-system providers for the commercially insured population. Data Sources: Physician membership in health systems was obtained from a unique longitudinal database on health systems and matched at the provider level to 2014 all-payer claims data from Colorado, Massachusetts, Oregon, and Utah. Study Design: Using an observational study design, we compared physicians in health systems to non-system physicians located in the same state and geography on average cost of care (risk-adjusted using the Johns Hopkins&apos; Adjusted Clinical Grouper), five HEDIS quality measures, one measure of developmental screening, and two Prevention Quality Indicator Measures. Data Collection/Extraction Methods: Patients in commercial health plans were attributed to a primary care physician accounting for the plurality of office visits. A cohort for each quality measure was constructed based on appropriate measure specifications. Principal Findings: The share of physicians in health systems increased steadily from 2012 to 2016 and ranged from 48% in Colorado to 63% in Utah in 2016. Compared to physicians not in a system, system physicians performed similarly on most HEDIS quality metrics compared to non-system physicians. Patients attributed to in-system physicians had about 40% higher rates (P < .05) of Ambulatory Care Sensitive Admissions (measured in admissions per 100 000:921.33 in-system vs 674.61 not-in-system for acute composite; 2540.91 in-system vs 1972.17 for chronic composite In-system providers were associated with $29 (P < .05) higher average per member per month costs (453.37 vs 432.93). Overall, differences in performance by system membership were relatively small compared to differences across states and geography. Conclusion: A growing share of physicians is part of a health system from 2012 to 2016. Providers in health systems are not delivering primary care more efficiently than non-system providers for the commercially insured. KEYWORDS cohort studies, geography, health care cost, ownership, primary care, quality of health care