A Comparison of Six Approaches for Measuring Utility Values Among Patients With Locally Advanced Cervical Cancer: a Cross-sectional Study

Abstract

Background: A variety of instruments to measure health utilities are available. Nevertheless, there was a lack of agreement between utility scores generated by the different instruments. To avoid difference in estimates of cost-effectiveness arising from the use of different instruments, it is essential to know whether these widely used instruments can be used interchangeable or not. While Euro-Quality of Life Five-Dimension (EQ-5D) is recommended as a preferred instrument for measuring health utilities there is no clear consensus on the preferred version of EQ-5D. Besides EQ-5D, time-trade-off (TTO), and visual analog scale (VAS) were commonly used instruments. This study aims to investigate agreement and performance of the following 6 utilities measures; EQ-5D-3L, EQ-5D-5L (cTTO Model), EQ-5D-5L (DCE Model), EQ-5D-5L (Hybrid model), TTO, and VAS among patients with locally advanced cervical cancer in Thailand. Methods: Face-to-face interview were conducted with 194 locally advanced cervical cancer patients. Comparison of median utility scores derived from the 6 approaches was made using Friedman test. The agreement of utility scores between each pairwise comparison was assessed by intraclass correlation coefficient (ICC) and Bland-Altman plot. Known-validity was determined by comparing two known groups with respect to status of treatment (i.e. treatment, disease free, and progression), and presences of symptoms (no symptoms, 1 symptom, and > 1 symptoms). Results: The mean (SD) utility values derived from the 6 approaches were, from low to high, 0.755±0.248 (EQ-5D-3L), 0.801±280 (TTO), 0.806±0.156 (VAS), 0.871±0.184 (cTTO model), 0.875±0.168 (Hybrid model), and 0.900±0.142 (DCE model). Intraclass correlation coefficient showed high agreement between EQ-5D-5L and EQ-5D-3L and very high agreement between all 3 models of EQ-5D-5L. Bland-Altman plots showed wide limit of agreement except the pairwise comparison between each model of the EQ-5D-5L; cTTO model and DCE model, cTTO model and Hybrid model, and DCE model and Hybrid. All 6 approaches can significantly differentiate treatment status and presence of symptoms.Conclusions: The commonly used utility measures, which are TTO, VAS, EQ-5D-3L and EQ-5D-5L cannot be used interchangeable among locally advanced cervical cancer patients. High agreement was found only between each pairwise comparison of the 3 value sets of EQ-5D-5L.