title: Assessing outcomes for cost-utility analysis in mental health interventions: mapping mental health specific outcome measure GHQ-12 onto EQ-5D-3L.
abstract: BACKGROUND
  Many intervention-based studies aiming to improve mental health do not include a multi-attribute utility instrument (MAUI) that produces quality-adjusted life-years (QALYs) and it limits the applicability of the health economic analyses. This study aims to develop 'crosswalk' transformation algorithm between a measure for psychological distress General Health Questionnaire (GHQ-12) and MAUI EuroQoL (EQ-5D-3L).
  
  
  METHODS
  The study is based on a survey questionnaire sent to a random sample in four counties in Sweden in 2012. The survey included GHQ-12 and EQ-5D instruments, as well as a question about self-rated health. The EQ-5D index was calculated using the UK and the Swedish tariff values. Two OLS models were used to estimate the EQ-5D health state values using the GHQ-12 as exposure, based on the respondents (n = 17, 101) of two counties. The algorithms were applied to the data from two other counties, (n = 15, 447) to check the predictive capacity of the models.
  
  
  RESULTS
  The final models included gender, age, self-rated health and GHQ-12 scores as a quantitative variable. The regression equations explained 40 % (UK tariff) and 46 % (Swedish tariff) of the variances. The model showed a satisfying predictive capacity between the observed and the predicted EQ-5D index score, with Pearson correlation = 0.65 and 0.69 for the UK and Swedish models, respectively.
  
  
  CONCLUSIONS
  The algorithms developed in this study can be used to determine cost-effectiveness of services or interventions that use GHQ-12 as a primary outcome where the utility measures are not collected.
authors.affiliation: Department of Public Health and Clinical Medicine, Epidemiology and Global Health, Umeå University, Umeå, Sweden.|Department of Statistics, Umeå University, Umeå, Sweden.
authors.forename: Marie
authors.initials: M
authors.lastname: Lindkvist
authors.affiliation: Department of Women's and Children's Health, Uppsala University, Uppsala, Sweden. inna.feldman@kbh.uu.se.
authors.forename: Inna
authors.initials: I
authors.lastname: Feldman
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D003362:Cost-Benefit Analysis; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008605:Mental Health Services / Q000191:economics*; D008875:Middle Aged; D008962:Models, Theoretical; D017063:Outcome Assessment, Health Care / Q000191:economics*; D019057:Quality-Adjusted Life Years; D011795:Surveys and Questionnaires; D013548:Sweden; D055815:Young Adult
keywords: Mapping; Mental health; Preference-based measures; Quality of life; Utilities