Questionnaire Modifications and Alternative Scoring Methods of the Dermatology Life Quality Index: A Systematic Review

Objectives: Dermatology Life Quality index (DLQI) is the most widely used health-related quality of life questionnaire in dermatology. Little is known about existing questionnaire or scoring modifications of the DLQI. We aimed to systematically review, identify, and categorize all modified questionnaire versions and scoring methods of the DLQI. Methods: We performed a systematic literature search in PubMed, Web of Science, CINAHL, and PsychINFO. Methodologic quality and evidence of psychometric properties were assessed using the Consensus-Based Standards for the Selection of Health Measurement Instruments (COSMIN) and Terwee checklists. Results: The included 81 articles reported on 77 studies using 59 DLQI modifications. Modifications were used for a combined sample of 25 509 patients with 47 different diagnoses and symptoms from 28 countries. The most frequently studied diseases were psoriasis, hirsutism, acne, alopecia, and bromhidrosis. The modifications were categorized into the following nonmutually exclusive groups: bolt-ons or bolt-offs (48%), disease, symptom, and body part specifications (42%), changes in existing items (34%), scoring modifications (27%), recall period changes (19%), response scale modifications (15%), and illustrations (3%). The evidence concerning the quality of measurement properties was heterogeneous: 4 of 13 studies were rated positive on internal consistency, 1 of 3 on reliability, 3 of 5 on content validity, 9 of 22 on construct validity, 6 of 6 on criterion validity, and 1 of 1 on responsiveness. Conclusion: An exceptionally large number of DLQI modifications have been used that may indicate an unmet need for adequate health-related quality of life instruments in dermatology. The psychometric overview of most questionnaire modifications is currently incomplete, and additional efforts are needed for proper validation.