Volume 55 | Number S3 | December 2020

Abstract List

Ruohua Annetta Zhou PhD, Nancy D. Beaulieu PhD, David Cutler PhD


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 ( < .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 ( < .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.


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.