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Background: In clinical studies, the EQ-5D-5L is often employed with disease-specific health-related quality of life instruments. The questions in the former are more general than the latter; however, it is known that responses to general questions can be influenced by preceding specific questions. Thus, the responses to the EQ-5D-5L have the possibility of being influenced by the preceding disease-specific health-related quality of life instruments. This may lead to bias in the cost-effectiveness analysis results. Therefore, this study aimed to evaluate the impact of the preceding cancer-specific health-related quality of life instruments on the EQ-5D-5L responses. Methods: We prepared questionnaire booklets containing the EQ-5D-5L, the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30, and the Functional Assessment of Cancer Therapy General with different orders. Using a quasi-randomized design, they were distributed to the patients undergoing drug therapy for advanced cancer, who were classified into three groups: Groups 1, 2, and 3 (the EQ-5D-5L placed first, second, and last, respectively). We compared the EQ-5D-5L index and the missingness of EQ-5D-5L among the groups. Results: The mean EQ-5D-5L index was 0.796, 0.760, and 0.789 for groups 1 (n = 300), 2 (n = 306), and 3 (n = 331), respectively. The difference between Groups 2 and 1 was − 0.036 (95% CI − 0.065 to − 0.007; p = 0.015). The proportion of patients with an incomplete EQ-5D-5L was 0.11, 0.11, and 0.05 for Groups 1, 2, and 3, respectively. The difference of the proportions between group 3 and 1 and between 3 and 2 was − 0.06 (95% CI − 0.10 to − 0.02; p = 0.003) and − 0.06 (95% CI − 0.10 to − 0.02; p = 0.003), respectively. Conclusions: Although the EQ-5D-5L index differed according to the instrument orders, the difference size would not be considerably larger than the minimally important difference. The patients tended to complete the EQ-5D-5L when they were placed at the end of the questionnaire. [ABSTRACT FROM AUTHOR]

Background: To develop direct and indirect (response) mapping algorithms from the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30) and the Functional Assessment of Cancer Therapy General (FACT-G) onto the EQ-5D-5L index.Methods: We conducted the QOL-MAC study where EQ-5D-5L, EORTC QLQ-C30, and FACT-G were cross-sectionally evaluated in patients receiving drug treatment for solid tumors in Japan. We developed direct and indirect mapping algorithms using 7 regression methods. Direct mapping was based on the Japanese value set. We evaluated the predictive performances based on root mean squared error (RMSE), mean absolute error, and correlation between the observed and predicted EQ-5D-5L indexes.Results: Based on data from 903 and 908 patients for EORTC QLQ-C30 and FACT-G, respectively, we recommend two-part beta regression for direct mapping and ordinal logistic regression for indirect mapping for both EORTC QLQ-C30 and FACT-G. Cross-validated RMSE were 0.101 in the two methods for EORTC QLQ-C30, whereas they were 0.121 in two-part beta regression and 0.120 in ordinal logistic regression for FACT-G. The mean EQ-5D-5L index and cumulative distribution function simulated from the recommended mapping algorithms generally matched with the observed ones except for very good health (both source measures) and poor health (only FACT-G).Conclusions: The developed mapping algorithms can be used to generate the EQ-5D-5L index from EORTC QLQ-C30 or FACT-G in cost-effectiveness analyses, whose predictive performance would be similar to or better than those of previous algorithms. [ABSTRACT FROM AUTHOR]