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

BACKGROUND: The Dermatology Life Quality Index (DLQI) rates 'not relevant' responses (NRRs) as the item on the questionnaire having no impact on the patients' lives at all. The DLQI-Relevant (DLQI-R) is a recently developed scoring that adjusts the total score of the questionnaire for the number of NRRs indicated by a patient. OBJECTIVES: To compare the discriminatory power of the original and DLQI-R scoring approaches in terms of absolute and relative informativity. METHODS: Cross-sectional data from 637 patients with morphea, pemphigus and psoriasis were used for the analyses. To assess absolute and relative informativity, Shannon's index and Shannon's evenness index were calculated for the 10 items on 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 subset of patients with NRRs (n = 261, 41%), absolute informativity was higher with the DLQI-R scoring for all eight items with NRR options in all three conditions. The DLQI-R exhibited a better relative informativity in 8, 8 and 6 items in pemphigus, morphea and psoriasis, respectively. The DLQI-R led to an improvement 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 relative informativity in all three conditions. CONCLUSIONS: In patients with morphea, pemphigus and psoriasis, DLQI-R scoring improves the discriminatory power of the questionnaire by benefiting from the additional information in NRRs. DLQI-R scoring may be useful both in clinical practice and research. A scoring chart has been developed to aid physicians with scoring. What's already known about this topic? The original scoring of the Dermatology Life Quality Index (DLQI) rates 'not relevant' responses as the item of the questionnaire having no impact on the patients' lives at all. DLQI-Relevant (DLQI-R) is a new scoring developed in 2018 that adjusts the total score of the questionnaire for the number of 'not relevant' responses indicated by patients. The discriminatory power of the DLQI-R compared with the DLQI has not yet been investigated. What does this study add? In patients with psoriasis, pemphigus and morphea, DLQI-R scoring improves the discriminatory power of the questionnaire by benefiting from the additional information in 'not relevant' responses. What are the clinical implications of this work? DLQI-R scoring may help to more accurately quantify patients' health-related quality of life both in clinical practice and research. A scoring chart has been developed to aid physicians with scoring.

Proposal of a new scoring formula for the Dermatology Life Quality Index in psoriasis.

BACKGROUND: 'Not relevant' responses (NRRs) on the Dermatology Life Quality Index (DLQI) may occur in up to 40% of patients with psoriasis. As these responses are scored as the item of the questionnaire having no impact on the patients' lives at all, it is more difficult for these patients to fulfil the DLQI > 10 criterion required by clinical guidelines to become candidates for systemic treatment including biologics. OBJECTIVES: We propose a new scoring system for the DLQI that corrects for the bias in the NRR option and test its construct validity in a sample of patients with psoriasis. METHODS: Data from 242 patients (104 of whom marked at least one NRR) from two earlier cross-sectional surveys were reanalysed. For each patient, the DLQI score was calculated in two ways: (i) according to the original scoring and (ii) by applying a new scoring formula (DLQI-R) that adjusts the total score for the number of NRRs. The construct validity of the DLQI-R was tested against the Psoriasis Area and Severity Index (PASI) and EQ-5D-3L. RESULTS: The mean DLQI and DLQI-R scores were 9·99 ± 7·52 and 11·0 ± 8·02, respectively. The DLQI-R allowed eight more patients (3·3%) to achieve the 'PASI > 10 and DLQI > 10' threshold. The results were robust when limiting the maximum number of NRRs allowed to two or three. Compared with the DLQI, DLQI-R correlated slightly better with PASI (rs = 0·59 vs. 0·57) and EQ-5D-3L index scores (rs = -0·58 vs. -0·54). CONCLUSIONS: The DLQI-R seems to be a valid scoring system for avoiding the bias in the NRR option and can help to improve patients' access to biologics.

A detailed analysis of 'not relevant' responses on the DLQI in psoriasis: potential biases in treatment decisions.

BACKGROUND: Dermatology Life Quality Index (DLQI) is the most common health-related quality of life measure in dermatology that is widely used in treatment guidelines for psoriasis. Eight of the 10 questions of the DLQI offer a 'not relevant' response (NRR) option that is scored as the item had no impact on patients' life at all. OBJECTIVE: To explore the occurrence of NRRs on the DLQI in psoriasis patients and to examine the effect of several socio-demographic and clinical factors on giving NRRs. METHODS: Data were obtained from two cross-sectional surveys among psoriasis patients at two academic dermatology clinics in Hungary. Health-related quality of life was measured by employing DLQI and EQ-5D-3L, while disease severity was graded by Psoriasis Area and Severity Index (PASI). Multivariate logistic regression was applied to determine the predictors of providing NRRs. RESULTS: Mean age of the 428 patients was 49 years, and 65% were males. Mean PASI, DLQI and EQ-5D-3L index scores were 8.4 ± 9.5, 6.8 ± 7.4 and 0.74 ± 0.28, respectively. Overall, 38.8% of the patients had at least one NRR: 19.6% (one), 11.5% (two), 5.1% (three) and 2.6% (more than three). Most NRRs occurred in sport, sexual difficulties and working/studying items of the DLQI (28.4%, 16.4% and 14.0%, respectively). Female gender (OR 1.65; 95% CI 1.04-2.61), older age (OR 1.05; 95% CI 1.03-1.07) and higher PASI score (OR 1.03; 95% CI 1.01-1.06) were associated with providing more NRRs, whereas highly educated patients (OR 0.34; 95% CI 0.16-0.72) and those with a full-time job (OR 0.47; 95% CI 0.29-0.77) less frequently tended to tick NRRs. CONCLUSION: The high rate of psoriasis patients with NRRs, especially among women, less educated and elderly patients, indicates a content validity problem of the measure. A reconsideration of the use of the DLQI for medical and financial decision-making in psoriasis patients is suggested.