Quality-of-Life Scales: Who Determines the Individual Item Weights and Does It Matter: Lessons Learned from the ALSQOL-ll

Quality-of-life (QOL) scales with externally imposed weights given to the individual items to derive a composite score have been contrasted with scales in which the patients determine the weights. We recently developed an l l-item, disease-specific, QOL scale for patients with ALS, the ALSQOL-ll, and elected to compare both approaches to item weighting. The crude ALSQOL-ll score is the sum of the individual item scores. The 64 patients who participated in validating the ALSQOL-ll were asked also to rank the items in order of importance to them. Patients varied widely in their individual priorities. However, average ranks were remarkably stable across several administrations of the scales, with breathing the highest at 2.24 and climbing the lowest at 8.29. Crude ALSQOL-ll scores were highly correlated with scores weighted based either on individual ranks (r = 0.94, P < 0.0001) or on average ranks (r = 0.98, P < 0.0001). The weighted and crude scores showed similar, statistically significant, correlations to previously described, standard, generic, and disease-specific QOL measures. We conclude that the question of externally imposed versus patient-determined item weights in QOL scales may be tested empirically. If both weighting systems perform equally well, externally imposed weighting may be adequate, resulting in QOL scales that are simpler for patients to use.