The Canadian SF-36 health survey: normative data add to its value.

Project was initiated, under the leadership of John Ware of the Health Institute at Boston's New England Medical Center. Its goals were to translate and validate, and obtain normative data using the Medical Outcomes Study 36-item Short Form (SF-36), a generic measure of health status or health-related quality of life for use in international studies. 1 At that time, parts of the IQOLA Project were underway in Sweden and Great Britain, and in 1992 similar studies started in several European and Aus-tralasian countries as well as in Canada. The number of nation members has increased since then, and today investigators in over 40 countries have translated and evaluated the SF-36, or are in the process of doing so. 2 The Canadian team, working in both official languages, performed the translation (adaptation) following a standard process and formally tested the assumptions underlying item scoring and the construction of multi-item scales. 3 The third step — to provide country-specific normative data — was not done because of financial constraints. It was therefore with great interest that I read the article by Wil-ma Hopman and colleagues in this issue (page 265). 4 Not only did they generate norms for the Canadian population using the SF-36, they were cleverly able to do so using data collected for another purpose. Establishing norms is an important step in the translation and cultural adaptation of a scale. Because the absolute number of a scale score has little meaning by itself, norms provide anchors to interpret an individual's or a group's score in relation to those of others. 5 Thus, scores can be understood as departures from typical values. 6 Several studies have demonstrated the worth of norms in assessing the impact of disease. 7–9 Normative data also enable comparisons within and between countries, to compare scores from a specific patient sample in one country with those from a matched patient sample in another. 10 In the same way, norms permit comparisons of the relative benefits of different treatments of various diseases between centres in a country or between countries. Hopman and colleagues obtained the Canadian norma-tive data from a nationally representative sample of adults aged 25 years or more living in the community. The SF-36 was given to participants to complete at the end of a struc-tured interview, which included questions about sociodem-ographic and clinical information and about health and personal behaviour. The process clearly met IQOLA …