SF-36 health survey reliability, validity and norms for New Zealand

Objective: To assess the acceptability, reliability and validity of the SF- 36 health survey in the New Zealand population and provide key population n orms. Method: The SF-36 questionnaire was part of the 1996/97 New Zealand health survey, a cross-sectional, nationally representative survey of 7,862 adults (15 years and over). Results: Overall, in the New Zealand population the questionnaire performed as well as or better than in other national surveys, but there was variabi lity in data completeness across subgroups, and responses were skewed towar ds the healthy end of the scales. Males scored higher than females on almos t all scales; increasing age was associated with decreasing scores (with th e exception of the mental health scale); and New Zealand Europeans tended t o report better health than the other ethnic groups. Conclusions: Satisfactory psychometric performance was demonstrated for the SF-36 in the New Zealand population, but researchers need to find ways of increasing data completeness in population groups shown here to have lower completion rates. The questionnaire may be better at discriminating patient rather than population subgroups. The SF-36 normative data confirm in kind , if not in degree, population subgroup disparities in health status observ ed using objective measures. Implications: Overall, the SF-36 questionnaire appears to be a valid and re liable measure of health-related quality of rife for the New Zealand popula tion. However, this paper highlights issues for researchers using the SF-36 , such as the skewed nature of responses obstained in a population sample.