The 15-D Measure of Health Related Quality of Life. II Feasibility, Reliability and Validity of its Valuation System

The 15D is a generic, 15-dimensional, standardised, self-administered measure of health-related quality of life (HRQOL), that can be used as a profile and single index score measure. This paper introduces alternative valuation models based on the multi-attribute utility theory for generating the single index scores, and examines their feasibility, reliability and validity by using several data sets and methods. Valuations were elicited from several representative samples of Finnish adult population by using rating scales in self-administered questionnaires and postal survey. The approach proved to be feasible and produced valuations with a high reliability. There is solid convergent evidence of construct validity for the index scores generated by additive 2-stage or 3stage valuation models. Tests for reflective equilibrium provided strong evidence that these scores exhibit a more plausible trade-off between length and quality of life than some other single index score measures (EuroQol, QWB, McMaster), and are thus more valid for QALY calculations in cost-utility analysis. The values are consistent and quite likely widely generalisable and usable at least in Western-type societies. The 15D is thus probably the most sensitive and comprehensive HRQOL measure presently available that combines the advantages of a profile and single index score measure with a high level of reliability and validity. The 15-D Measure of Health Related Quality of Life. II Feasibility, Reliability and Validity of its Valuation System