Variation in the risk of readmission among hospitals: the relative contribution of patient, hospital and inpatient provider characteristics

Abstract

Background: The risk of readmission varies among hospitals. This variation has led the Centers of Medicare and Medicaid services to reduce payments to hospitals with excess readmissions. The contribution of patient characteristics, hospital characteristics and provider type to the variation in risk of readmission among hospitals has not been determined.

Objective: To describe the variation in risk of readmission among hospitals and partition it by patient characteristics, hospital characteristics and provider type.

Design: Retrospective research design of 100% Texas Medicare data using multilevel, multivariable models.

Subjects: A total of 514,064 admissions of Medicare beneficiaries to 272 hospitals in Texas for medical diagnoses during the years 2008 and 2009.

Main measures: Using hierarchical generalized linear models, we describe the hospital-specific variation in risk of readmission that is attributable to patients characteristics, hospital characteristics and provider type by measuring the variance and intraclass correlation coefficients.

Key results: Of the total variation in risk of readmission, only a small amount (0.84%) is attributed to hospitals. In further analyses modeling the components of this variation among hospitals, differences in patient characteristics in the hospitals explained 56.2% of the variation. Hospital characteristics and the type of provider explained 9.3% of the variation among hospitals and 0.08% of the total variation in risk of readmission.

Conclusions: Patient characteristics are the largest contributor to variation in risk of readmission among hospitals. Measurable hospital characteristics and the type of inpatient provider contribute little to variation in risk of readmission among hospitals.

Figure 1

Cohort selection.

Figure 2

Unadjusted 30-day readmission rates for the 272 Texas hospitals, by rank from lowest to highest. The horizontal line represents the overall mean. Error bars represent standard deviation estimated by the normal approximation to the binomial distribution.

Figure 3

Unadjusted (red) and adjusted (blue) 30-day readmission rates for the 272 Texas hospitals, by rank from lowest to highest. The adjusted rates were estimated from a multilevel model adjusting for patient characteristics, including age, sex, race, Medicaid eligibility, ER admission, weekend admission, MDC, DRG weights, 29 comorbid conditions, any nursing home stay in the prior 90 days, number of hospitalizations, number of outpatient physician visits, and presence of an identifiable PCP in the prior year.

Figure 4

Sources of variation in 30-day risk of readmission among hospitals with at least 1,500 admissions.