PRM4 QALY and Productivity Loss: Empirical Evidence for “Double Counting”

Abstract

Some insist that productivity loss should not be included in costs when using quality-adjusted life year (QALY) because QALY also reflects the influence of work loss and thus results in “double counting.” “Double counting” of QALY and productivity loss is a controversial issue, particularly given the lack of empirical data addressing the influence of income reduction on utility scores. In this study, we performed a web-based, large-sample survey to address the issue of double counting. To determine the influence of income reduction on utility scores, we obtained utility scores of eight health states with three instruction types: a) no instruction; b) instructed to consider income reduction; and c) instructed not to consider income reduction (compensated). Respondents were randomly sampled from the on-line panel adjusted by age and sex. They were asked to evaluate one of 24 patterns by both standard gamble (SG) and time trade-off (TTO) methods. A total of 6551 respondents completed the questionnaire. Respondent demographics were similar to the Japanese general population. First, despite the lack of instruction on income reduction, many respondents spontaneously assumed lost income. The proportion tended to be higher when considering more severe health states. Second, the degree of assumed income reduction was related to utility scores. For a 10% income reduction, respondents assumed a 0.02 to 0.04 decrease in utility score (both SG and TTO methods). Third, utility scores did not change significantly, even when the decrease in income was compensated. In our view, the effect of income does not only reflect money they lost. An assumed income reduction clearly influenced utility scores, however compensation for lost income fail to improve utility scores. Our results suggest that income does not significantly influence utility scores and that the impact of double counting is negligible.