title: Are Improvements in Measured Performance Driven by Better Treatment or "Denominator Management"?
abstract: BACKGROUND
  Process measures of healthcare quality are usually formulated as the number of patients who receive evidence-based treatment (numerator) divided by the number of patients in the target population (denominator). When the systems being evaluated can influence which patients are included in the denominator, it is reasonable to wonder if improvements in measured quality are driven by expanding numerators or contracting denominators.
  
  
  OBJECTIVE
  In 2003, the US Department of Veteran Affairs (VA) based executive compensation in part on performance on a substance use disorder (SUD) continuity-of-care quality measure. The first goal of this study was to evaluate if implementing the measure in this way resulted in expected improvements in measured performance. The second goal was to examine if the proportion of patients with SUD who qualified for the denominator contracted after the quality measure was implemented, and to describe the facility-level variation in and correlates of denominator contraction or expansion.
  
  
  METHODS
  Using 40 quarters of data straddling the implementation of the performance measure, an interrupted time series design was used to evaluate changes in two outcomes.
  
  
  METHODS
  All veterans with an SUD diagnosis in all VA facilities from fiscal year 2000 to 2009.
  
  
  METHODS
  The two outcomes were 1) measured performance-patients retained/patients qualified and 2) denominator prevalence-patients qualified/patients with SUD program contact.
  
  
  RESULTS
  Measured performance improved over time (P < 0.001). Notably, the proportion of patients with SUD program contact who qualified for the denominator decreased more rapidly after the measure was implemented (p = 0.02). Facilities with higher pre-implementation denominator prevalence had steeper declines in denominator prevalence after implementation (p < 0.001).
  
  
  CONCLUSIONS
  These results should motivate the development of measures that are less vulnerable to denominator management, and also the exploration of "shadow measures" to monitor and reduce undesirable denominator management.
authors.affiliation: Center for Innovation to Implementation, VA Palo Alto Health Care System, 795 Willow Road, Menlo Park, CA, 94025, USA. Alexander.Harris2@va.gov.
authors.forename: Alex H S
authors.initials: AH
authors.lastname: Harris
authors.affiliation: Center for Innovation to Implementation, VA Palo Alto Health Care System, 795 Willow Road, Menlo Park, CA, 94025, USA.
authors.forename: Cheng
authors.initials: C
authors.lastname: Chen
authors.affiliation: Center for Innovation to Implementation, VA Palo Alto Health Care System, 795 Willow Road, Menlo Park, CA, 94025, USA.
authors.forename: Anna D
authors.initials: AD
authors.lastname: Rubinsky
authors.affiliation: VA Greater Los Angeles Health Care System and University of California Los Angeles, Los Angeles, CA, USA.
authors.forename: Katherine J
authors.initials: KJ
authors.lastname: Hoggatt
authors.affiliation: Center for Innovation to Implementation, VA Palo Alto Health Care System, 795 Willow Road, Menlo Park, CA, 94025, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Neuman
authors.affiliation: Center for Innovation to Implementation, VA Palo Alto Health Care System, 795 Willow Road, Menlo Park, CA, 94025, USA.|Center for Health Policy/Primary Care and Outcomes Research, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: Megan E
authors.initials: ME
authors.lastname: Vanneman
mesh_terms: D019468:Disease Management; D005260:Female; D006801:Humans; D008297:Male; D011787:Quality of Health Care / Q000191:economics / Q000592:standards*; D012052:Reimbursement, Incentive / Q000191:economics / Q000592:standards*; D016320:Substance Abuse Treatment Centers / Q000191:economics / Q000592:standards*; D019966:Substance-Related Disorders / Q000191:economics / Q000453:epidemiology / Q000628:therapy*; D016896:Treatment Outcome; D014481:United States; D014493:United States Department of Veterans Affairs / Q000191:economics / Q000592:standards*; D014728:Veterans
keywords: measurement reactivity; performance contracts; quality measurement