title: Effect of patient selection method on provider group performance estimates.
abstract: BACKGROUND
  Performance measurement at the provider group level is increasingly advocated, but different methods for selecting patients when calculating provider group performance have received little evaluation.
  
  
  OBJECTIVE
  We compared 2 currently used methods according to characteristics of the patients selected and impact on performance estimates.
  
  
  METHODS
  We analyzed Medicare claims data for fee-for-service beneficiaries with diabetes ever seen at an academic multispeciality physician group in 2003 to 2004. We examined sample size, sociodemographics, clinical characteristics, and receipt of recommended diabetes monitoring in 2004 for the groups of patients selected using 2 methods implemented in large-scale performance initiatives: the Plurality Provider Algorithm and the Diabetes Care Home method. We examined differences among discordantly assigned patients to determine evidence for differential selection regarding these measures.
  
  
  RESULTS
  Fewer patients were selected under the Diabetes Care Home method (n=3558) than the Plurality Provider Algorithm (n=4859). Compared with the Plurality Provider Algorithm, the Diabetes Care Home method preferentially selected patients who were female, not entitled because of disability, older, more likely to have hypertension, and less likely to have kidney disease and peripheral vascular disease, and had lower levels of predicted utilization. Diabetes performance was higher under Diabetes Care Home method, with 67% versus 58% receiving >1 A1c tests, 70% versus 65% receiving ≥1 low-density lipoprotein (LDL) test, and 38% versus 37% receiving an eye examination.
  
  
  CONCLUSIONS
  The method used to select patients when calculating provider group performance may affect patient case mix and estimated performance levels, and warrants careful consideration when comparing performance estimates.
authors: Department of Population Health Sciences, University of Wisconsin, Madison, WI 53705, USA. cthorpe@wisc.edu
authors: Carolyn T
authors: CT
authors: Thorpe
authors: Grace E
authors: GE
authors: Flood
authors: Sally A
authors: SA
authors: Kraft
authors: Christine M
authors: CM
authors: Everett
authors: Maureen A
authors: MA
authors: Smith
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