Purpose: The EQ-5D is a generic questionnaire generating a health profile and a single index score for health-related quality of life. This study aimed to analyse the discriminative ability and validity of the EQ-5D in patients with schizophrenic, schizotypal or delusional disorders.
Subjects and methods: One hundred sixty-six patients with schizophrenic, schizotypal or delusional disorders (ICD-10 F2) completed the EQ-5D. Measures of quality of life (WHOQOL-BREF), utility (TTO), subjective (SCL-90R) and objective (PANSS, CGI-S) psychopathology, and functioning (GAF, GARF, SOFAS, HoNOS) provided comparison. Discriminative ability was analysed by assessing frequency distributions of EQ-5D scores. Validity of the EQ-5D self-classifier was analysed by assessing differences in related other scores grouped by response levels of EQ-5D items. Validity of the visual analogue scale (EQ VAS) and the EQ-5D index (UK social tariff) was analysed by assessing their correlation with all other scores.
Results: Seventy-nine percent of respondents reported problems in at least one of the EQ-5D dimensions (anxiety/depression 57%, usual activities 45%, pain/discomfort 44%, self-care 29%, mobility 22%). The mean EQ VAS score/EQ-5D index was 65.7/0.71. The four most frequently reported EQ-5D health states covered 45% of all respondents. For almost all EQ-5D dimensions, different response levels were associated with significantly different scores of measures used for comparison. Correlation of EQ VAS score and EQ-5D index were largest with scores of subjective measures (SCL-90R: -0.50 and -0.73; WHOQOL mental subscore 0.62 and 0.58; always P<0.001).
Discussion and conclusion: The EQ-5D showed a moderate ceiling effect and seems to be reasonably valid in this patient group.