Abstract

Direct and indirect preference-based methods are two main types of utility generating methods which are being frequently used in cost-utility analysis. However, a key question is how do these two methods perform in terms of validity? The aim of this study is to assess the utilities derived from EuroQol five-dimensional 5 level (EQ-5D-5L) as an indirect method and composite time trade-off (C-TTO) as a direct method in patients with colorectal cancer (CRC). A total of 223 patients with CRC were consecutively selected from three cancer centers in Tehran between May and September 2017. The EQ-5D-5L and C-TTO methods were used to estimate utilities in patients. Wilcoxon test was performed to compare utilities between C-TTO and EQ-5D-5L. In addition, intraclass correlation coefficient (ICC) and Bland-Altman plot were used to assess the agreement between the two methods. Bootstrapping quantile regression analysis was performed for comparison coefficient. The mean values of EQ-5D-5L (0.7186 +/- 0.1275) for all stages were significantly higher than the C-TTO (0.4180 +/- 0.4670) values. Stage 1 had the highest utility in both C-TTO (0.8167 +/- 0.2332) and EQ-5D-5L (0.8339 +/- 0.0535), whereas stage 4 had the lowest utility (0.1283 +/- 0.5530 and 0.6001 +/- 0.1220, respectively). As well, the C-TTO underestimates the values in low level of utilities and overestimates in high level of utilities. The overall ICC between the two methods was 0.50. Our study provides some tentative results about the differences between values of EQ-5D-5L and C-TTO, but clearly more work is needed to be done on this issue.