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Purpose Eight of the ten items of the Dermatology Life Quality Index (DLQI) have a ‘not relevant’ response (NRR) option. There are two possible ways to interpret NRRs: they may be considered ‘not at all’ or missing responses. We aim to compare the measurement performance of the DLQI in psoriasis patients when NRRs are scored as ‘0’ (hereafter zero-scoring) and ‘missing’ (hereafter missing-scoring) using Rasch model analysis. Methods Data of 425 patients with psoriasis from two earlier cross-sectional surveys were re-analysed. All patients completed the paper-based Hungarian version of the DLQI. A partial credit model was applied. The following model assumptions and measurement properties were tested: dimensionality, item fit, person reliability, order of response options and differential item functioning (DIF). Results Principal component analysis of the residuals of the Rasch model confirmed the unidimensional structure of the DLQI. Person separation reliability indices were similar with zero-scoring (0.910) and missing-scoring (0.914) NRRs. With zero-scoring, items 6 (sport), 7 (working/studying) and 9 (sexual difficulties) suffered from item misfit and item-level disordering. With missing-scoring, no misfit was observed and only item 7 was illogically ordered. Six and three items showed DIF for gender and age, respectively, that were reduced to four and three by missing-scoring. Conclusions Missing-scoring NRRs resulted in an improved measurement performance of the scale. DLQI scores of patients with at least one vs. no NRRs cannot be directly compared. Our findings provide further empirical support to the DLQI-R scoring modification that treats NRRs as missing and replaces them with the average score of the relevant items.

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.

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.

Abstract: Introduction: The health status and health-related quality of life (HRQoL) of patients with psoriasis in Hungary are understudied. Aim: To assess HRQoL in psoriasis patients, to compare HRQoL of psoriasis patients to that of the general public in Hungary and to identify predictors of HRQoL. Method: Between 2012 and 2016, two cross-sectional surveys were carried out among psoriasis patients at two academic dermatology departments. HRQoL was assessed by EQ-5D-3L, EQ Visual Analogue Scale (EQ VAS) and Dermatology Life Quality Index (DLQI). Predictors of HRQoL were analysed by multivariate linear regression. Results: 434 patients were enrolled (mean age 49 years, 65% male, 81% moderate-to-severe psoriasis, 43% treated with biologics). Mean EQ-5D-3L, EQ VAS and DLQI scores were 0.74 ± 0.28, 69.06 ± 20.98 and 6.78 ± 7.38, respectively. Overall, 54%, 43%, 40%, 32% and 15% of patients indicated at least some problems in pain/discomfort, anxiety/depression, mobility, usual activities and self-care. EQ-5D-3L index scores in patients were lower compared to the age- and gender-matched general population in Hungary. The difference was statistically significant for the age groups 25–34 and 45–64 in males, and 18–64 in females (p

The purpose of this study is to assess the measurement properties of EQ-5D-5L compared to EQ-5D-3L in psoriasis patients. A cross-sectional survey was carried out at an academic dermatology clinic in Hungary. Psoriasis patients completed the EQ-5D-3L, EQ-5D-5L and Dermatology Life Quality Index (DLQI) questionnaires, and Psoriasis Area and Severity Index (PASI) was assessed. The UK value sets were used to calculate the 3L and 5L index scores. We tested the feasibility, ceiling effect, redistribution properties, the level of inconsistency and informativity (Shannon and Shannon Evenness indices). Spearman’s rank-order correlations were performed between EQ-5D, EQ VAS, DLQI and PASI scores. Known-groups validity was evaluated by comparing age groups, clinical subtypes and treatment groups. Mean age of the 238 patients was 47 years, and 36.6% of them received biological therapy. Mean EQ-5D index score was 0.77 (SD: 0.26) with the 3L and 0.84 (SD: 0.19) with the 5L. The overall ceiling effect decreased from 37.1 (3L) to 32.9% (5L). Shannon index improved significantly for most dimensions, but Shannon Evenness index improved only in three dimensions. Compared to the 3L, the 5L version confirmed a better convergent validity with PASI, but not with the DLQI. Known-groups validity was equally demonstrated both for the 5L and 3L. The EQ-5D-5L seems to improve measurement properties by reducing ceiling effects, strengthening correlations with PASI and improving informativity. Follow-up studies are needed to test responsiveness and reliability in psoriasis.

In many jurisdictions, deterioration in quality of life assessed with Dermatology Life Quality Index (DLQI) is used for medical and reimbursement decisions in various dermatological conditions such as psoriasis. However, utility values for health states defined by the DLQI have not yet been evaluated. Therefore, we aim to estimate utilities for different health states described by the ten items of the DLQI. A cross-sectional survey was performed in a convenience sample of the general population. Seven DLQI health states with total scores of 6, 11 and 16 (3–3 and 1 states, respectively) were developed. All of them were different from each other in the number of affected items and severity levels of impairment. The 10-year time trade-off method was used to value health states. Mean utilities elicited by the respondents (n = 308) for the three 6-, three 11- and one 16-point DLQI health states were 0.62–0.75, 0.59–0.66, and 0.56, respectively. In half of the six pairwise comparisons, where health states with the same total DLQI score were compared, significant difference between utilities was found. In eight out of the 15 comparisons between health states with different DLQI scores, utilities were not significantly different. Utility values for health states with identical DLQI total score may significantly vary. This result might be generalisable to various patient populations, in which the DLQI is used; nevertheless, further research is needed. The discrepancies between DLQI scores and utilities might have an impact on medical and reimbursement decisions as they make the utility gain from treatment uncertain.

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 out 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. This article is protected by copyright. All rights reserved.

Dermatology Life Quality Index (DLQI) is the most commonly applied measure of health-related quality of life (HRQoL) in psoriasis patients. It is among defining criteria of moderate-to-severe psoriasis and present in treatment guidelines. Our objective was to estimate preference-based HRQoL values (i.e., utilities) for hypothetical health states described by the 10 items of the DLQI in psoriasis patients. Moreover, we compare results to findings of a similar study previously conducted among the general public. A cross-sectional survey was carried out among 238 psoriasis patients. Seven hypothetical DLQI-defined health states with total scores of 6, 11, and 16 (3–3 and 1 states, respectively) were evaluated by time trade-off method. The difference in DLQI scores between hypothetical health states was set at 5 points, as it exceeds the minimal clinically important difference (MCID). Utility scores were found to be homogenous across the seven hypothetical health states (range of means for the 6-point states 0.85–0.91, range of means for the 11-point states 0.83–0.85, and mean of 0.84 for the 16-point state). Overall, mean utilities assessed by psoriasis patients were higher for all seven states compared with the general public (mean difference 0.16–0.28; p