Does the EQ-5D capture the concerns measured by the Palliative care Outcome Scale? Mapping the Palliative care Outcome Scale onto the EQ-5D using statistical methods.

The main measure to generate utility data for economic evaluations is the EQ-5D, but no study has tested whether or how to map from palliative care measures to the EQ-5D.To assess the level of conceptual overlap between palliative outcomes and the EQ-5D, and the feasibility of mapping between them to obtain utilities for the Palliative care Outcome Scale.A cross-sectional secondary analysis of data from three studies.Patients receiving palliative care and bereaved relatives, recruited from three tertiary National Health Service hospitals in South London.The overlap between both measures was assessed using principal component analysis. The Palliative care Outcome Scale was mapped onto the EQ-5D using three regression models.Spearman's correlations between both instruments were low (mean rho = 0.11). The principal component analysis showed the Palliative care Outcome Scale is associated with only two EQ-5D dimensions (pain; and anxiety/depression). No Palliative care Outcome Scale items loaded onto the mobility, self-care and usual activities dimensions of the EQ-5D. The mapping models performed poorly at predicting utilities from Palliative care Outcome Scale data (mean absolute error >0.3 and R <0.10). Hence, none of the models can be recommended as acceptable for calculating utilities from Palliative care Outcome Scale responses.Differences between the Palliative care Outcome Scale and the EQ-5D do not undermine the qualities of either instrument when used for their own purposes. However, due to conceptual differences, the EQ-5D does not capture some of the concerns measured by the Palliative care Outcome Scale, and therefore, mapping onto the EQ-5D is unlikely to provide an appropriate basis for estimating utilities for conducting economic evaluations in palliative care studies.