[How useful is the calculation of total scores for questionnaires concerning health related quality of life?].
Questionnaires for health related quality of life generally comprise several subscales. These subscales can be summarized into a total score. The aim of this article is to test the justification of such an integration from a statistical point of view. By means of a representative sample of the German population (n = 1981) the correlative relationships among six questionnaires are assessed: NHP, EORTC QLQ-C30, HADS, MFI-20, GBB-24 and Whiteley index. The corrrelations between the total scores are markedly higher than the mean correlations among the subscales between the tests. Even in those cases where the subscales share the same subdimension the correlations are not higher than the correlations between these subscales and the (unspecific) total scores. The advantage of sharing a common area is as great as the disadvantage of the lower number of items. By means of the Spearman-Brown formula the relationship between the number of items and the reliability of the scale is discussed in detail. It can be concluded that the calculation of total scores is useful and justified from a statistical perspective.