OBJECTIVES: The objective was to perform the validation of the Spanish EQ-5D-5L questionnaire for patients with major depression disorder, studying the psychometric properties, such as reliability and validity, including the structural validation.

METHODS: We included 433 patients with major depression, who completed the EQ-5D-5L, the BDI-II and the PHQ-9 questionnaires. The EQ-5D-5L contains five questions rated on a five-level scale, from which a utility index can be derived based on the recently developed preference-based scoring function (Ramos-Goñi et al. 2016). The BDI-II consists of 21 items conforming a global score, in addition to classifying patients according to their severity. The PHQ-9 allows to establish the diagnosis and severity of the depression. Statistical analysis: Floor and ceiling effects were examined. Reliability was assessed using Cronbach’s alpha coefficient. Structural validity was studied by confirmatory factor analysis (CFA) for categorical data. Convergent validity was studied by the Spearman correlation coefficient between EQ-5D-5L and BDI-II. We examined known-groups validity by comparing the EQ-5D-5L index among the different severity groups according to the BDI-II and PHQ-9 using the analysis of variance or Kruskal-Wallis test.

RESULTS: The floor and ceiling effects in EQ-5D-5L index were 0% and 3.94%, respectively. Cronbach’s alpha coefficient was 0.77. The fit indexes of the CFA were excellent (RMSEA=0.036, CFI=0.999, TLI=0.995) and factor loadings were all statistically significant and >0.60. The correlation between the EQ-5D-5L index and BDI-II was -0.58. Patients with higher severity level, had significantly lower scores on the EQ-5D-5L (P<0.0001).

CONCLUSIONS: The results support the reliability and validity of the EQ-5D-5L questionnaire in patients with major depression disorder. Further, the hypothesis that the five items of the questionnaire make up a single factor (the utility index) is confirmed. Therefore, the recently derived EQ-5D-5L, could be very useful as an outcome measure, at least in patients with major depression disorder.