Appropriateness of the EQ-5D-5L in capturing health-related quality of life in individuals with transfusion-dependent β-thalassemia: a mixed methods study

Individuals with transfusion-dependent β-thalassemia (TDT) experience symptoms and functional impacts that reduce their health-related quality of life. However, EQ-5D-derived health utility index scores in TDT often indicate good HRQoL, suggesting the EQ-5D may not adequately capture the impact of TDT. This study explored the disease and treatment burden of TDT and examined the appropriateness of the EQ-5D-5L descriptive system (DS) in measuring HRQoL in TDT. Adults with TDT in the United Kingdom, United States, and France completed a background questionnaire and EQ-5D-5L DS, followed by 60-minute semi-structured interviews on symptoms and HRQoL impacts of TDT (concept elicitation) and appropriateness of EQ-5D-5L DS (cognitive debrief). Transcribed interviews were analyzed using thematic and content analyses. The relationship between TDT symptoms and impacts were summarized in a conceptual model. EQ-5D-5L DS was mapped to concepts identified in the qualitative data to assess its capture of HRQoL concepts. Participants' EQ-5D-5L DS scores were compared to their qualitative descriptions for each dimension to assess their concordance. Thirty participants in the United States (n = 14 [46.7%]), United Kingdom. (n = 12 [40.0%]), and France (n = 4 [13.3%]) completed the study (73.3% female; mean age = 28.4 years [standard deviation (SD) = 5.1]; mean annual red blood cell transfusion [RBCT] frequency = 18.4 [SD = 7.6]). Participants reported TDT symptoms and impacts on HRQoL, all fluctuating across the RBCT cycle. EQ-5D-5L DS did not fully capture 11 of 16 (68.8%) HRQoL concepts reported. Most participants (n = 20/27 [74.1%]) reported that EQ-5D-5L DS did not capture important aspects of living with TDT, and 42.9% (n = 12/28) reported negative/neutral overall impressions of EQ-5D-5L DS. The highest degree of discordance between participants' qualitative data and EQ-5D-5L DS dimension scores was observed with mobility (42.3%) and self-care (34.6%), where the qualitative descriptions relating to these dimensions were worse than their quantitative scores. Current findings suggest that EQ-5D-5L DS lacks content validity and the derived health utility index score may not fully represent the burden of disease in TDT.