Mapping the Schizophrenia Quality of Life Scale to EQ-5D, HUI3 and SF-6D utility scores in patients with schizophrenia

Abstract

Objectives The current study aimed to map the disease-specific Schizophrenia Quality of Life Scale (SQLS) onto the three- and five-level EuroQol five-dimension (EQ-5D-3L and EQ-5D-5L), Healthy Utility Index Mark 3 (HUI3) and Short Form six-dimensional (SF-6D) preference-based instruments to inform future cost-utility analyses for treatment in patients with schizophrenia. Methods Data from 251 outpatients with schizophrenia spectrum disorders was included for analysis. Ordinary least square (OLS), Tobit and beta regression mixture models (betamix) were employed to estimate the utility scores. Model selection of 66 regression models (regression methods x six model specifications) was determined by goodness of fit and predictive indices. Distribution of the original data to the distributions of the data generated using the preferred estimated models were then compared. Results EQ-5D-3L and EQ-5D-5L were best predicted by the OLS model, including SQLS domain scores, domain scores-squared, age, and gender as explanatory predictors. The models produced the best performance index and resemble more closely to the observed EQ-5D data. HUI3 and SF-6D were best predicted by the OLS and Tobit model respectively. Conclusion The current study developed mapping models for converting SQLS scores into generic utility scores, which can be used in economics evaluation in schizophrenia patients.