Validation and application of the Dermatology Life Quality Index score, a modification of the DLQI score, in psoriasis patients.

Background: All the scoring methods for the DLQI miss the moderate impact of the disease on patients, which may underestimate the impact of psoriasis on patients' quality of life. To improve the accuracy of the assessment of the Dermatology Life Quality Index score (DLQI) for patients with psoriasis, this study proposed and validated a new scoring method, the DLQI-NS, which includes the moderate impact option in the self-assessment of each item in psoriasis patients.

Methods: A cross-sectional study was conducted in which patients with psoriasis were enrolled. A total of 425 participants completed the DLQI, DLQI-NS and Skindex-16 questionnaires. Reliability, validity, ceiling and floor effects were evaluated of both DLQI and DLQI-NS questionnaires.

Results: About 14.4-32.5% of the patients reported a moderate impact on quality of life. The DLQI-NS allowed 17 more patients (4.0%) to achieve severe disease. The Cronbach's alpha coefficient of the DLQI-NS was 0.90, and that of the DLQI was 0.89. The KMO test results for the DLQI-NS and DLQI were 0.927 and 0.916, respectively. One factor was identified for each questionnaire. The items of the DLQI-NS showed an item-total correlation from 0.52 to 0.82, and the DLQI questionnaire's item-total correlation ranged from 0.47 to 0.83. The DLQI-NS, DLQI total score and Skindex-16 had Spearman's rank correlation coefficients of 0.89 and 0.84, respectively. Both the DLQI-NS and DLQI showed significant moderate correlations with the BSA (0.51 vs. 0.50) and PASI (0.47 vs. 0.46). No ceiling effects were observed for any of the items of both questionnaires.

Conclusion: The validity and reliability of the DLQI-NS and DLQI were good, but the DLQI-NS was superior to the DLQI. The DLQI-NS is an effective self-assessment tool for assessing quality of life in psoriasis patients.