title: Can choice of the sample population affect perceived performance: implications for performance assessment.
abstract: BACKGROUND
  There is accelerating interest in measuring and reporting the quality of care delivered by health care providers and organizations, but methods for defining the patient panels for which they are held accountable are not well defined.
  
  
  OBJECTIVE
  To examine the potential impact of using alternative algorithms to define accountable patient populations for performance assessment.
  
  
  METHODS
  We used administrative data regarding Community Health Center (CHC) visits in simulations of performance assessment for breast, cervical, and colorectal cancer screening.
  
  
  METHODS
  Fifteen CHC sites in the northeastern US.
  
  
  METHODS
  We used three different algorithms to define patient populations eligible for measurement of cancer screening rates and simulated center-level performance rates based on these alternative population definitions.
  
  
  RESULTS
  Focusing on breast cancer screening, the percentage of women aged 51-75 eligible for this measure across CHCs, if using the most stringent algorithm (requiring a visit in the assessment year plus at least one visit in the 2 years prior), ranged from 28% to 60%. Analogous ranges for cervical and colorectal cancer screening were 18-59% and 26-62%, respectively. Simulated performance data from the centers demonstrate that variations in eligible patient populations across health centers could lead to the appearance of large differences in health center performance or differences in expected rankings of CHCs when no such differences exist. For instance, when holding performance among similar populations constant, but varying the proportion of populations seen across different health centers, simulated health center adherence to screening guidelines varied by over 15% even though actual adherence for similar populations did not differ.
  
  
  CONCLUSIONS
  Quality measurement systems, such as those being used in pay-for-performance and public reporting programs, must consider the definitions used to identify sample populations and how such populations might differ across providers, clinical practice groups, and provider systems.
authors: Department of Health Care Policy, Harvard Medical School, 180 Longwood Avenue, Boston, MA 02215, USA. landon@hcp.med.harvard.edu
authors: Bruce E
authors: BE
authors: Landon
authors: A James
authors: AJ
authors: O'Malley
authors: Thomas
authors: T
authors: Keegan
mesh_terms: D000328:Adult; D000368:Aged; D003151:Community Health Centers / Q000592:standards*; D055088:Early Detection of Cancer / Q000379:methods / Q000592:standards*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010465:Perception; D010865:Pilot Projects; D011159:Population Surveillance / Q000379:methods; D011785:Quality Assurance, Health Care / Q000379:methods / Q000592:standards*; D055815:Young Adult