DLQI-R scoring improves the discriminatory power of theDermatology Life Quality Index in patients with psoriasis,pemphigus and morphea

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Abstract

Background The Dermatology Life Quality Index (DLQI) rates ‘not relevant’responses (NRRs) as the item on the questionnaire having no impact on thepatients’ lives at all. The DLQI-Relevant (DLQI-R) is a recently developed scoringthat adjusts the total score of the questionnaire for the number of NRRs indicatedby a patient.Objectives To compare the discriminatory power of the original and DLQI-R scor-ing approaches in terms of absolute and relative informativity.Methods Cross-sectional data from 637 patients with morphea, pemphigus andpsoriasis were used for the analyses. To assess absolute and relative informativity,Shannon’s index and Shannon’s evenness index were calculated for the 10 itemson the questionnaire and for DLQI and DLQI-R total scores.Results Mean DLQI and DLQI-R scores of patients were 613 vs. 691. In the su b-set of patients wit h NRRs (n = 261, 41%), absolute informativity was higherwith the DLQI-R scoring for all eight items with NRR options in all three condi-tions. The DLQI-R exhibited a better relative informativity in 8, 8 and 6 items inpemphigus, morphea and psoriasis, respectively. The DLQI-R led to an improve-ment in average item-level informativity in all DLQI score bands up to 20 points.Regarding total scores, the DLQI-R produced both a higher absolute and relativeinformativity in all three conditions.Conclusions In patients with morphea, pemphigus and psoriasis, DLQI-R scoringimproves the discriminatory power of the questionnaire by benefiting from theadditional informa tion in NRRs. DLQI-R scoring may be us eful both in clinicalpractice and research. A scoring chart has been developed to aid physicians withscoring.