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

Abstract

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’ 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