Development of a direct weighting procedure for quality of life domains.

The Schedule for the Evaluation of Individual Quality of Life allows individuals to nominate the domains they consider most important to their quality of life and to use their own value system when describing the functional status and relative importance of those domains. The weights for domain importance are derived through a procedure called judgement analysis. As judgement analysis is impractical for individuals with cognitive impairment and in many clinical situations, a shorter, direct weighting procedure has been developed. To test the new procedure, 40 healthy individuals completed both direct and judgement analysis weightings, at t1 and 7-10 days later (t2). After a further 7-10 days (t3), they were asked to identify the weight profiles they had previously produced using each method. The weights produced by the two methods differed on average by 7.8 points at t1 and 7.2 points at t2. The direct weights changed on average by 4.5 points from t1 to t2, while the judgement analysis weights changed by 8.4 points. At t2, 55% of individuals were able to identify the direct weights they had previously produced. The new procedure demonstrates stability and validity but is not interchangeable with judgement analysis. The most appropriate ways of using and interpreting both procedures are discussed.