Construct validity of EQ-5D-5L among patients with inflammatory bowel disease-a study based on real-world data from the Swedish Inflammatory Bowel Disease Registry.

Objectives: The Swedish Inflammatory Bowel Disease Registry (SWIBREG) includes approximately 84% of all patients with inflammatory bowel disease (IBD) treated with immunomodulators, biologics or surgery in Sweden. Data on health-related quality of life (HRQoL) have been collected using EQ-5D-5L in the registry since 2012. Nevertheless, there are few studies assessing the validity of EQ-5D-5L in this patient population. Thus, the aim of this study was to assess the construct validity of EQ-5D-5L amongst patients with IBD (ulcerative colitis and Crohn's disease).

Methods: Individual-level data on EQ-5D-5L and other disease-specific measures were extracted from SWIBREG. Known-groups validity was assessed by analysing whether the EQ-5D-5L captured expected differences between patient groups with different activity levels of the disease. Convergent validity was assessed by analysing whether the reported problems in the dimensions of EQ-5D-5L, EQ VAS, and the EQ-5D-5L index value correlated, as hypothesized, with the four dimensions in the Short Health Scale, a symptom index question, and the Physician Global Assessment (PGA) score.

Results: In total, 9769 patients with IBD were included in the study. Patients with active IBD reported more health problems in the EQ-5D-5L descriptive system than patients being in remission. The effect sizes for the differences in reported problems between patients with active and inactive disease were at least small (≥0.1) or medium (≥0.3) in all dimensions except self-care. Differences in the mean EQ-5D-5L index and EQ-VAS score between patients with active and inactive disease were statistically significant (p < 0.001) and larger than pre-defined cut-offs for minimally important differences (>0.08 for the index and >11.0 for EQ-VAS). The analysis of convergent validity showed that EQ-5D-5L results correlated as expected with the disease-specific measures in 16 of the 21 analyses. In total, 22 (79%) of the 28 hypotheses were supported.

Conclusion: The findings support the construct validity of EQ-5D-5L amongst patients with IBD and contribute to the scarce literature on the validity of the five-level version of EQ-5D in this patient population. These findings have important implications for the choice of HRQoL measure in routine health care registries like SWIBREG as well as for future clinical or health economic studies considering using EQ-5D-5L as a measure of HRQoL.