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

To assess the acceptability, reliability and validity of the SF-36 health survey in the New Zealand population and provide key population norms.

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).

Overall, in the New Zealand population the questionnaire performed as well as or better than in other national surveys, but there was variability in data completeness across subgroups, and responses were skewed towards the healthy end of the scales. Males scored higher than females on almost all scales; increasing age was associated with decreasing scores (with the exception of the mental health scale); and New Zealand Europeans tended to report better health than the other ethnic groups.

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 observed using objective measures.

Overall, the SF-36 questionnaire appears to be a valid and reliable measure of health-related quality of life for the New Zealand population. However, this paper highlights issues for researchers using the SF-36, such as the skewed nature of responses obstained in a population sample.