The responsiveness of the EQ-5D and time trade-off scores in schizophrenia, affective disorders, and alcohol addiction

Abstract

Objective: To compare the responsiveness of the EQ-5D index (German and British tariff), the EQ-5D visual analogue scale (EQ VAS), and time trade-off (TTO) scores in schizophrenia, affective disorders, and alcohol addiction. Methods: We used a sample of 502 patients and examined the measures at baseline and after 14 months. We used the generic "WHO Quality of Life BREF" (WHOQOL) and the disorder-specific "Global Severity Index" (GSI) as anchors for a relevant improvement in a patient's health status. In a complete case analysis, we assessed the responsiveness, which is the ability to detect a change given a relevant change on the anchor. We computed the effect sizes (ESs) and standardised response means (SRMs). Results: In patients with schizophrenia, the ESs and SRMs were large (ES/SRM > 0.8) for the British EQ-5D index (ESGSI: 0.93; SRMGSI: 0.89; SRMWHOQOL: 0.82). In patients with affective disorders, we found large ESs and SRMs for the EQ VAS (ESGSI: 1.79; ESWHOQOL: 0.90; SRMGSI: 1.52; SRMWHOQOL: 0.93) and a large ES for the British EQ-5D index (ESGSI: 0.88). In patients with alcohol addiction, the ESs and SRMs were large for the EQ VAS (ESGSI: 1.40; ESWHOQOL: 0.94; SRMGSI: 1.04; SRMWHOQOL: 0.83). The ESs and SRMs of the German EQ-5D index were consistently lower than those of the British EQ-5D index. Regarding TTO score, ESs and SRMs were generally less than 0.5. Conclusions: No preference-based instrument was consistently more responsive than others across all mental disorders. While the EQ VAS was the most responsive instrument in patients with affective disorders or alcohol addiction, the British EQ-5D index was reasonably responsive in patients with schizophrenia.