Some considerations concerning negative values for EQ-5D health states

Abstract

In this discussion paper we bring together a number of considerations which might be relevant to gain insight into the use of negative values for EQ-5D health states. This seems relevant since the introduction of negative values will inevitably lead to a discussion about these values, and the background to these figures has to be explained and documented. In theory and in practice it is possible to avoid the use of negative values even in cases where states are considered to be worse than death (WTD). However if one prefers to avoid explicit negative values for EQ-5D health states, other issues arise and it seems to us to be important to have an understanding of these issues. It is possible to understand the nature of the issues involved because the results and data of the MVH project are available. We consider this project as a milestone in the work on quality of life measurement and wish to make explicit our admiration for this scientific endeavour. It is only because of this project that the EuroQol Group is in a position to discuss tariffs based on a large empirical study in which several measurement methods were applied. Our discussion is thus to be seen as an effort to gain insight into the subtleties of the subject and we hope to contribute to the fruitful and widespread use of the results of the project. The issues raised by the negative values for EQ-5D health states are complex and relevant arguments derive from the fields of psychology, statistics, economics, ethics, and political science. Since it is nearly impossible for somebody who is trained in one of these disciplines to have a clear understanding of all the issues, a discussion at the level of the Group seems to be a fruitful way to obtain a fuller picture. In this paper, the UK Al and A2 tariffs are chosen as a starting point. The results are derived using the Time Trade Off (TTO) method and will be seen by the EuroQol Group and others as nicely fitting into the framework of economic project appraisal. Some elements might also be relevant for VAS tariffs, but for the purposes of this discussion it was decided to concentrate on the Al and A2 tariffs.