Comparing the performance of the EQ-5D-5L with two versions of the SF-6Dv2 in patients with breast cancer

The EQ-5D-5L and two versions of the SF-6D version 2 (i.e., SF-6Dv2ind-10 that is derived from 10 items of the SF-36v2, and SF-6Dv2SF-36 that is derived from its combination with the full SF-36v2) are used to drive utilities. The study was prospected to compare the performance of these instruments in breast cancer patients. Data were gathered from 418 patients with breast cancer using three questionnaires including the EQ-5D-5L, SF-36v2, and SF-6Dv2ind-6. The differences between the mean utilities of instruments were tested by t-test. The correlation between the dimensions scores of instruments was estimated by Spearman’s correlation coefficient (ρ). The level of agreement between the instruments score was assessed by ICC and Bland–Altman plot. The correlations between theoretically related pairs of EQ-5D-5L and SF-6Dv2SF-36 were stronger than those of the EQ-5D-5L and SF-6Dv2ind-6. The ICC between EQ-5D-5L and SF-6Dv2ind-6 was 0.64, and between EQ-5D-5L and SF-6Dv2SF-36 was 0.48. The Bland–Altman plot showed that there was a poorer agreement on the lower values. The EQ-5D-5L had more similarity with the SF-6Dv2ind-6 in comparison with the SF-6Dv2SF-36. Nevertheless, there are still significant differences between them.