In or out? Income losses in health state valuations: a review.

BACKGROUND: In 1996 the Washington Panel controversially recommended valuing productivity costs (PC) in terms of quality-adjusted life years. The Panel's assumption that respondents in health state valuation (HSV) exercises take income losses into account could not be countered since there was no evidence regarding what people consider in HSV exercises. If they do consider income losses and if this changes HSVs, then all economic evaluations that have included PC in the numerator may have double-counted these costs. Alternatively, if respondents do not consider income losses then all past economic evaluations that have not included PC in the numerator have failed to account for sizeable societal costs.
OBJECTIVES: Through a review we aim to recapture the debate surrounding the appropriate method for including PC in health economic evaluations, to identify empirical evidence addressing the assumptions of the Panel, and recommend a future research agenda.
METHODS: Through a review we identify, outline, and critically appraise the existing empirical studies that attempt to address whether respondents include income effects in HSV exercises. RESULTS AND
CONCLUSION: Seven empirical studies were identified. Overall, it seems that not explicitly mentioning the inclusion of income will induce a minority of respondents to include these effects and this appears not to influence results. More empirical work is needed, using generic instruments, larger samples, and using the interview method of administration.