A Swedish population-based study on the relationship between the SF-36 and health utilities to measure health in hypertension

The aim of this study was to determine the relationship between a psychometric health-related quality-of-life instrument (the SF-36)-and two health utility measures [the time trade-off (TTO) and rating scale (RS) methods) among hypertensives in a general population. In the analyses were adjusted for co-morbidity. The study was based on a postal questionnaire that was sent to a random sample of 8000 inhabitants aged 20-84 years (response rate 68%) in Uppsala County, Sweden, in 1995. The results showed only a moderate correlation between the TTO and the RS methods. The different dimensions of SF-36 were overall lower correlated with the TTO method than with the RS method. Co-morbidity was not associated with the RS or the TTO method among hypertensives. The regression equations explained 58% of the variance in RS among hypertensives. The corresponding value for the TTO method was about 20%. In conclusion, our study found that among hypertensives the SF-36 is low to moderate correlated to the TTO and RS methods. Health utilities and psychometric measures represent different attributes of health. It is therefore important to be aware of the differences between psychometric and utility measures when interpreting results from studies using different methods. More work is needed to explicate if health utilities can be obtained from the SF-36.