Supplementary Material for: Dermatology Life Quality Index (DLQI) in patients with atopic dermatitis: Are ‘not relevant’ responses relevant?

Introduction: According to the DLQI user manual, the patients´ answers ‘not relevant’ (NR) and ‘not at all’ (affected in this aspect of life by the skin problem) are treated equally and interpreted as no impairment in health related quality of life (HRQoL). The aim of this study was to gain more insights about ‘not relevant’ responders with atopic dermatitis (AD). Methods: 3,353 patients with AD, recruited from dermatological offices and a patient organisation, were surveyed in three cross-sectional studies. Disease severity (SCORAD) and subjective health status (EQ VAS) were compared for each DLQI item between patients who answered ‘not relevant’ and all others according to their response category. Different DLQI scoring versions were analysed. Results: Those who stated ‘not relevant’ in terms of HRQoL limitations in the DLQI domains sports, work/study and sexual relationships were comparable in AD severity and health status to those who felt that their HRQoL was ‘a little affected’. Alternative DLQI scoring versions, in which ‘not relevant’ responses (NRRs) were interpreted as ‘a little affected’, correlated slightly higher with the SCORAD and EQ VAS than the original DLQI. Conclusion: Patients with AD who rate certain life domains as ‘not relevant’ in the DLQI are most similar in their disease burden to patients who feel a little affected in these areas of life. This suggests that some HRQoL limitations are underestimated by the traditional DLQI scoring. However, alternative scoring solutions have not shown substantially higher correlations with other disease burden criteria compared to the original. Therefore, the gain in validity by alternative scoring versions is small.