SF-6D, HUI3 trump EQ-5D at measuring quality of life in Asians with mental illness
The Short-Form Six-Dimension (SF-6D) and Health Utility Index Mark 3 (HUI3) appear to be more reliable than both the 3-level and 5-level EuroQol Five-Dimension (EQ-5D-3L and EQ-5D-5L, respectively) instrument at evaluating the quality of life (QOL) in Asians with mental health problems, according to a recent Singapore study.
“[T]he current study provides important evidence to clinicians and researchers about the best choice of generic preference-based measures that can be used to assess health-related QOL of patients with mental illness in an Asian patient population,” said researchers.
Five hundred individuals participated in the study, 251 of whom had schizophrenia spectrum disorder (mean age 39.88±10.24 years; 56.2 percent male) while the remaining 249 had depression (mean age 36.23±11.07 years; 52.6 percent male). The mean EQ-5D-5L, EQ-5D-3L, HUI3 and SF-6D utility scores were 0.76, 0.69, 0.55 and 0.65, respectively. [Psychiatry Res 2019;274:400-408]
Analysis of score distribution showed that only those from the SF-6D were normally distributed, while results from the other tests were skewed.
Test-retest reliability ranged from poor to excellent (intraclass correlation coefficient [ICC], 0.35–0.92). The SF-6D provided the best reliability in patients with schizophrenia spectrum disorder (ICC, 0.92) and in the overall sample (ICC, 0.83) but yielded the lowest score in patients with depression (ICC, 0.61).
In the latter group, HUI3 emerged as the most reliable instrument (ICC, 0.83). In comparison, the EQ-5D-3L instrument showed the lowest reliability both in patients with schizophrenia spectrum disorder (ICC, 0.35) and in the overall sample (ICC, 0.63).
In terms of convergent validity, which pertains to the degree to which the four generic measures agree with disease-specific instruments, the SF-6D utility scores showed the highest correlation with the psychosocial subdomain of the schizophrenia QOL scale (SQLS; coefficient, –0.68; p<0.001) in the group of patients with schizophrenia spectrum disorder.
On the other hand, in the depression group, the HUI3 instrument most strongly correlated with scores in the Quality of Life Enjoyment and Satisfaction Questionnaire (Q-LES-Q; coefficient, 0.79; p<0.001).
Researchers also evaluated the magnitude of change in scores, which measured the ability of an instrument to detect clinically important changes in patient status.
“In the schizophrenia spectrum disorder sample, except for HUI3, all utility scores tended to have higher mean scores after 6 months follow-up with a small effect size. The SF-6D seems to have slightly higher standardized response mean (SRM) than other utility scores. However, none of the mean difference showed clinically meaningful improvement,” they said.
Findings were similar for the depression sample, where instruments returned slightly higher scores after 6 months of follow-up, though none were of practical significance. The EQ-5D-5L appeared to yield a higher SRM than the other instruments.
Known-group validity, or the ability of the instrument to discriminate between mild and severe conditions, was also evaluated and showed that the SF-6D and HUI3 scales had the highest effect sizes for the schizophrenia spectrum disorder and depression subsamples, respectively.
“The direct comparison of four utility scores in patients with schizophrenia spectrum disorder and patients with depression demonstrated that the SF-6D and HUI3 utility scores could produce reliable, valid and high magnitude of change results when used in economic evaluation for measuring benefits of mental health interventions … in patients with schizophrenia spectrum disorders and patients with depressive disorders respectively,” said researchers.