Mapping the Positive and Negative Syndrome Scale scores to EQ-5D-5L and SF-6D utility scores in patients with schizophrenia

OBJECTIVE: The current study aims to map the Positive and Negative Syndrome Scale (PANSS) onto the five-level EuroQol five-dimensional (EQ-5D-5L) and Short Form six-dimensional (SF-6D) utility scores for patients with schizophrenia. METHODS: A total of 239 participants with schizophrenia spectrum disorder were recruited from a tertiary psychiatric hospital in Singapore. Ordinary least squares (OLS), censored least absolute deviations and Tobit regression methods were employed to estimate utility scores from the EQ-5D-5L and SF-6D. Model selection of the 18 regression models (three regression methods × six model specifications) was primarily determined by the smallest mean absolute error and mean square error, and the largest R(2) and adjusted R(2). RESULTS: The mean age of the sample was 39.7 years (SD = 10.3). The mean EQ-5D-5L and SF-6D utility scores were 0.81 and 0.68, respectively. The EQ-5D-5L utility scores were best predicted by the OLS regression model consisting of three PANSS subscales, i.e. positive, negative and general psychopathology symptoms, and covariates including age and gender. The SF-6D was best predicted by OLS regression model consisting of five PANSS subscales, i.e. positive, negative, excitement, depression and cognitive subscales. CONCLUSION: The current study provides important evidence to clinicians and researchers on mapping algorithms for converting PANSS scores into utility scores that can be easily applicable for cost–utility analysis when EQ-5D-5L and SF-6D data are not available for patients with schizophrenia spectrum disorder in Singapore. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s11136-018-2037-7) contains supplementary material, which is available to authorized users.