Impact of socioeconomic adjustment on physicians' relative cost of care

Abstract

Background: Ongoing efforts to profile physicians on their relative cost of care have been criticized because they do not account for differences in patients' socioeconomic status (SES). The importance of SES adjustment has not been explored in cost-profiling applications that measure costs using an episode of care framework.

Objectives: We assessed the relationship between SES and episode costs and the impact of adjusting for SES on physicians' relative cost rankings.

Research design: We analyzed claims submitted to 3 Massachusetts commercial health plans during calendar years 2004 and 2005. We grouped patients' care into episodes, attributed episodes to individual physicians, and standardized costs for price differences across plans. We accounted for differences in physicians' case mix using indicators for episode type and a patient's severity of illness. A patient's SES was measured using an index of 6 indicators based on the zip code in which the patient lived. We estimated each physician's case mix-adjusted average episode cost and percentile rankings with and without adjustment for SES.

Results: Patients in the lowest SES quintile had $80 higher unadjusted episode costs, on average, than patients in the highest quintile. Nearly 70% of the variation in a physician's average episode cost was explained by case mix of their patients, whereas the contribution of SES was negligible. After adjustment for SES, only 1.1% of physicians changed relative cost rankings >2 percentiles.

Conclusions: Accounting for patients' SES has little impact on physicians' relative cost rankings within an episode cost framework.

Appendix Figure 1

Distribution of SES Indexes for Included Episodes of Care and Physician-level Mean SES

Appendix Figure 2

Distributions of SES Index Components for Included Patients and the Overall Adult Population Note: Red denotes included patients. Blue denotes the overall adult population living in the same zip codes.

Figure 1. Unadjusted Cost per Episode of Care, by Quintile of Patients’ SES Index

Notes: Each data point corresponds to the mean unadjusted cost per episode of care and is neither adjusted for case mix nor SES).

Figure 2. Change in Physicians’ Relative Cost Rankings following Adjustment for Patients’ SES Index

Notes: n refers to the number of physicians who changed relative cost rankings by the number of percentiles indicated.