title: Development of the EXACT-U: a preference-based measure to report COPD exacerbation utilities.
abstract: BACKGROUND
  The exacerbations of chronic obstructive pulmonary disease tool (EXACT) is a condition-specific daily diary recently developed to evaluate the frequency, severity, and duration of chronic obstructive pulmonary disease (COPD) exacerbations. A preference-based algorithm for the EXACT would allow utilities to be reported from patients during an exacerbation when EQ-5D data are not available.
  
  
  OBJECTIVE
  To develop the exacerbations of chronic obstructive pulmonary disease tool-utility (EXACT-U), a condition-specific preference-based measure to report utilities from the EXACT for use in cost-effectiveness studies.
  
  
  METHODS
  Five items with three to five levels comprise the EXACT-U. Two groups of health states and respondents were constructed to allow for model development (Development group) and predictive validity testing (Validation group) using independent samples. Members of the UK general public each valued 11 randomized health states using time trade-offs (TTOs) scaled from full health/dead with 10-year durations. Regression models estimated from the Development group using individual data, mean data, and panel designs. Models assessed by number of inconsistent coefficients estimated and R(2) and tested against observed utilities from the Validation group using mean absolute error (MAE) and root mean squared error (RMSE).
  
  
  RESULTS
  A total of 55 health states, including the best and worst states, were valued in TTO interviews conducted with 400 respondents. Ten models were developed. The final preferred model contained no logical inconsistencies and found MAE = 0.04 and RMSE = 0.05 with a predicted utility range from 0.09 to 0.95.
  
  
  CONCLUSIONS
  The EXACT-U is a condition-specific preference-based measure with strong predictive validity to report daily utilities during an exacerbation.
authors.affiliation: Department of Health Services Research and Policy, London School of Hygiene and Tropical Medicine, London, UK. Jennifer.Petrillo@lshtm.ac.uk
authors.forename: Jennifer
authors.initials: J
authors.lastname: Petrillo
authors.forename: John
authors.initials: J
authors.lastname: Cairns
mesh_terms: D000328:Adult; D018450:Disease Progression; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D008297:Male; D008499:Medical Records / Q000592:standards*; D008875:Middle Aged; D011237:Predictive Value of Tests; D029424:Pulmonary Disease, Chronic Obstructive / Q000453:epidemiology* / Q000473:pathology; D011788:Quality of Life / Q000523:psychology; D012720:Severity of Illness Index; D006113:United Kingdom / Q000453:epidemiology; D014894:Weights and Measures / Q000592:standards; D055815:Young Adult