Objectives: The aim of this study was to estimate an empirical relationship and degree of agreement between the TTO values of patients' own health and their 15D scores.
Methods: A total of 863 hospital patients aged 18-93 years filled in the 15D questionnaire to establish their 15D score and valued their present health with TTO. Wilcoxon signed rank test, the Spearman rank correlation coefficient and Tobit models were used to analyze the relation between the 15D and TTO scores.
Results: The null hypothesis of no tendency for one set of scores to be higher or lower than the other set could not be rejected. Apart from dummies for few patients groups, no additional information to the 15D score was found that would have explained significantly the variance in the TTO valuations of patients' own health. The agreement between these to sets of scores turned out quite good at the aggregate level.
Conclusions: To the extent that mean TTO valuations of patients own health are valid for QALY calculations as they at least theoretically should be, and if experience of health states to be valued counts, the 15D scores are also valid without any transformation in a large group of heterogeneous patients. However, in certain patient groups, the agreement was not as good as overall.