Saturday, June 15, 2024

Impact of Peer Grouping on CMS Hospital Star Ratings

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The Centers for Medicare & Medicaid Services (CMS) Overall Star Rating serves as a critical tool for patients and consumers seeking to evaluate hospital quality. The 2021 revision introduced a peer grouping step that stratifies hospitals based on the number of measure groups they report. This study aimed to assess the effects of this peer grouping on the distribution of star ratings among hospitals.

Methodology and Participants

This cross-sectional study utilized data from the Care Compare website, focusing on 3076 hospitals that received a star rating in 2023. Analysis spanned from April to December 2023. Hospitals were segregated into three peer groups based on the number of measure groups with at least three reported measures, comparing star ratings with and without the peer grouping step.

The key outcome was the distribution of star ratings, ranging from one star (lowest performance) to five stars (highest performance). The study also investigated the number of hospitals whose star ratings increased, decreased, or remained unchanged due to peer grouping, further stratifying by hospital characteristics.


Among the 3076 hospitals evaluated, the majority were non-specialty (1994, 64.8%), nonteaching (1807, 58.7%), non-safety net (2326, 75.6%), and non-critical access (2826, 91.9%) hospitals with fewer than 200 beds (1822, 59.2%), predominantly located in urban areas (1935, 62.9%). The peer grouping step resulted in 585 hospitals (19.0%) receiving different star ratings compared to the method without peer grouping. Specifically, 517 hospitals received higher ratings, while only 68 received lower ratings.

Hospitals located in urban areas (351, 67.9%), non-safety net hospitals (414, 80.1%), and those with fewer than 200 beds (287, 55.6%) were more likely to receive higher star ratings when peer grouping was applied. The peer grouping step thus supports like-to-like comparisons among hospitals, aiding patients in better assessing hospital quality.

Key Inferences

  • Peer grouping enhances the accuracy of star ratings by enabling more equitable comparisons among hospitals.
  • Urban hospitals and non-safety net hospitals are more likely to benefit from higher star ratings with peer grouping.
  • Hospitals with fewer than 200 beds see significant improvements in star ratings when peer grouping is used.

The inclusion of peer grouping in the CMS star rating method has resulted in modest yet significant changes in hospital ratings. This adjustment improves face validity and aligns with stakeholders’ need for peer comparisons, making the current CMS Overall Star Rating method a reliable tool for assessing hospital performance.

Original Article: JAMA Netw Open. 2024 May 1;7(5):e2411933. doi: 10.1001/jamanetworkopen.2024.11933.

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