The Short-Form 36 (SF-36) Health Survey and its use in pharmacoeconomic evaluation

The Short-Form 36 (SF-36) Health Survey is a brief self-administered questionnaire that generates scores across 8 dimensions of health. It has been found to be reliable, and valid in terms of criteria such as agreement with clinical diagnosis and disease severity, but its underlying values have not been tested against patient preferences. The SF-36 was not devised for use in economic evaluation. The SF-36 may be used in cost-minimisation analyses, where the dimension scores can be shown to reflect people's values for health at an ordinal level, but it cannot be used in either cost-effectiveness or cost-utility analyses. The dimensions scores of zero to 100 do not provide a common currency and, where there is conflict between the dimension scores, there is no basis for establishing an overall health benefit. Furthermore, in clinical trials, the usual comparison is between mean or median scores, which assumes risk neutrality and does not take adequate account of the relationship between the value of health and time. Although they are under pressure to assess the cost effectiveness of healthcare interventions, researchers and policy analysts must resist short-cut methods of deriving a single index from the SF-36 that are based on arbitrary aggregation schemes, because these ignore people's preferences and the crucial quantity/quality trade-off, and therefore cannot be used in economic evaluations. However, the rich descriptive material and multidimensionality of the SF-36 may have potential for use in economic evaluation. Multi-attribute utility theory provides a way of deriving a single index based on elicited values, but it requires a major restructuring of the scales of the SF-36. Alternatively, SF-36 responses may provide material for constructing health scenarios that could then be valued on a holistic basis.