Validity of EQ-5D-5L, Skindex-16, DLQI and DLQI-R in patients with hidradenitis suppurativa

Abstract

Background: Numerous generic, skin- and disease-specific health-related quality of life (HRQoL) measures are available for patients with hidradenitis suppurativa (HS). Yet, robust psychometric evidence is lacking in many aspects of these outcome measures. Objectives: We sought to determine convergent and known-groups validity of multiple generic and skin-specific HRQoL measures and to identify predictors of impaired HRQoL in patients with HS. Methods: Between 2017 and 2019, a multicentre cross-sectional study was carried out involving 200 consecutive HS patients. HRQoL outcomes included the EQ-5D-5L, EQ visual analogue scale (EQ VAS), Skindex-16, Dermatology Life Quality Index (DLQI) and DLQI-Relevant (DLQI-R). Disease severity was graded by HS-Physician’s Global Assessment (HS-PGA) scale and the Modified Sartorius scale (MSS). Results: Overall, 77%, 56%, 51%, 46% and 28% reported problems in the pain/discomfort, usual activities, anxiety/depression, mobility and self-care dimensions of EQ-5D-5L. Mean ± SD EQ VAS, DLQI and DLQI-R scores were 64.29 ± 22.68, 11.75 ± 8.11 and 12.19 ± 8.33, respectively. Skindex-16 responses indicated that the emotional burden of HS (64.55 ± 29.28) far exceeded those of functioning (49.40 ± 34.70) and physical symptoms (46.74 ± 29.36). EQ-5D-5L, EQ VAS, DLQI, DLQI-R and Skindex-16 total scores had moderate or strong correlations with each other (range: |0.487| to |0.993|), weak or moderate correlations with HS-PGA (|0.350| to |0.433|) and weak correlations with MSS (|0.324| to |0.389|). DLQI-R slightly outperformed DLQI both in terms of convergent and known-groups validity. Being female, lower education level, more severe disease and genital involvement were associated with worse HRQoL (P < 0.05). Conclusion: This study provides high-quality evidence that among skin-specific outcomes, the DLQI, DLQI-R and Skindex-16, and among generic instruments, the EQ-5D-5L are suitable to be used in HS patients. In future research, we recommend the use of existing well-validated HRQoL tools instead of developing new measures for each study. The development of composite measures that combine physician- and patient-reported outcomes is not supported by evidence in HS. [Correction added on 25 July 2020, after first online publication: in the Abstract section, the ± signs were missing and have been added to this version.].