A methodological study was conducted to examine the effect of extending a frequently used simple multiattribute health-status classification system by adding a cognitive dimension. The EQ-5D questionnaire is a generic instrument to value health, developed by the EuroQol Group. The EQ-5D defines health according to five dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. We defined 18 different health states according to the standard EQ-5D classification. A second set of health states was constructed similar to the first, except for the addition of a cognitive dimension (EQ-5D+C). Valuations of both sets of health states were statistically analyzed to detect the effect of the additional dimension. The cognitive dimension generated systematically different values compared with the standard EQ-5D version, whereas the content validity improved. Both systems evoked equally reliable values. Analyses showed that a simple additive model to predict summary values for health states was not optimal for both systems. Although there is a current lack of consensus regarding the domains that are selected to represent health status, this study has shown the importance of considering the inclusion of a cognitive domain.

Cognitive dimension, EuroQol, Methodology, Multiattribute health-status classification systems, Reliability, Validity
dx.doi.org/10.1016/S0895-4356(98)00163-2, hdl.handle.net/1765/64416
Journal of Clinical Epidemiology
Department of Gynaecology & Obstetrics

Krabbe, P.F.M, Stouthard, J.M.L, Essink-Bot, M.L.E, & Bonsel, G.J. (1999). The effect of adding a cognitive dimension to the EuroQol multiattribute health-status classification system. Journal of Clinical Epidemiology, 52(4), 293–301. doi:10.1016/S0895-4356(98)00163-2