Testing the validity of the Euroqol and comparing it with the SF-36 health survey questionnaire

There is an interest in the consequences of deriving a single index measure of health for validity and sensitivity. This paper presents the results of testing a recent example of a general health measure designed to derive a single index, the Euroqol (EQ), and presents a comparison with a new, influential profile measure, the Short Form 36 (SF-36) Health Survey Instrument. The EQ and an anglicised version of the SF-36 health survey, both designed for self-completion, were included in a postal survey of a random sample of 1980 patients from two practice lists in Sheffield, UK. The response rate for the EQ questionnaire was 83%, and the rate of completion over 95%. Evidence was found for the construct validity of the EQ dimension responses and the derived total EQ health score in terms of distinguishing between groups with expected health differences. Considerable agreement was found between EQ responses and the total EQ score, and the UK SF-36 profile scores. There was substantial evidence of EQ being less sensitive at the ceiling (i.e. low levels of perceived ill-health) and throughout the range of health states. A recent restructuring of the EQ, may help overcome some of the problems with the physical dimensions by reducing their skewness.