Comparison of the measurement properties between a short and generic instrument, the 5-level EuroQoL Group’s 5-dimension (EQ-5D-5L) questionnaire, and a longer and disease-specific instrument, the Functional Assessment of Cancer Therapy—Breast (FACT-B), in Asian breast cancer patients
To compare the measurement precision and related properties between the 5-level EuroQoL Group’s 5-dimension (EQ-5D-5L) questionnaire and the Functional Assessment of Cancer Therapy—Breast (FACT-B) questionnaire in assessing breast cancer patients. An observational study of 269 Singaporean breast cancer patients. To compare discriminative ability and responsiveness, the effect sizes (in standard deviation) of the EQ-5D-5L and the FACT-B in relation to health indicators and the change in performance status or quality of life were estimated. Test–retest reliability was examined using the intraclass correlation (ICC). Using performance status, evidence of disease, and treatment status as the criteria, the differences (FACT-B minus EQ-5D-5L) in the effect size for discriminative ability were negative or closed to zero, and the 90 % confidence intervals totally fell within the zone that indicated the non-inferiority of the EQ-5D-5L. For responsiveness and test–retest reliability, the confidence intervals of the differences in effect size and ICC overlapped the non-inferiority margin; thus, non-inferiority in these two aspects could neither be confirmed nor rejected. The EQ-5D-5L was non-inferior to the FACT-B in discriminating breast cancer patients with different health conditions cross-sectionally. The EQ-5D-5L serves as a reasonable alternative or supplementary instrument to the FACT-B in assessing breast cancer patients’ health outcomes.