Psychometric validation of the Psoriasis Symptom Scale, Functional Assessment of Chronic Illness Therapy-Fatigue and pain-Visual Analogue Scale in patients with generalized pustular psoriasis.

BACKGROUND: Generalized pustular psoriasis (GPP) is a rare, chronic, inflammatory skin disease associated with considerable patient burden. The Psoriasis Symptom Scale (PSS), Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) and pain-Visual Analogue Scale (pain-VAS) are patient-reported outcomes (PROs) that have not yet been validated in patients with GPP. OBJECTIVES: To evaluate the psychometric properties of the PSS, FACIT-Fatigue and pain-VAS using data from Effisayil 1, a randomised trial of spesolimab in patients with moderate-to-severe GPP. METHODS: Inter-item correlations and confirmatory factor analysis (CFA) were performed using Week 1 data. Internal consistency was assessed with Cronbach's α coefficient using baseline and Week 1 data. Test-retest reliability was assessed using intraclass correlation coefficients (ICCs); change data for the GPP Physician Global Assessment total score and pustulation subscore were used to define a stable population. Convergent validity was assessed at baseline and Week 1 using Spearman's rank-order correlations. Known-groups validity was measured by analysis of variance using Week 1 data. Ability to detect change from baseline to Week 1 was evaluated by analysis of covariance. RESULTS: Inter-item and item-to-total correlations were moderate or strong for most PSS and FACIT-Fatigue items. CFA demonstrated the unidimensionality of the PSS and FACIT-Fatigue, with high factor loadings for most items (PSS range, 0.75-0.94; FACIT-Fatigue range, 0.11-0.93) and acceptable fit statistics. Both scores demonstrated internal consistency (Cronbach's α, 0.71 and 0.95, respectively). The PSS, FACIT-Fatigue and pain-VAS demonstrated test-retest reliability (ICCs ≥0.70) and good evidence of convergent validity. Furthermore, the PROs could differentiate between known groups of varying symptom severity (range, p < 0.0001-0.0225) and detect changes in symptom severity from baseline to Week 1 (range, p < 0.0001-0.0002). CONCLUSIONS: Overall, these results support the reliability, validity and ability to detect change of the PSS, FACIT-Fatigue and pain-VAS as PROs in patients with GPP.

Validation of the Peak Pruritus Numerical Rating Scale as a Patient-Reported Outcome Measure in Prurigo Nodularis.

INTRODUCTION: Validated patient report tools for quantifying patient experiences of itch in prurigo nodularis (PN) are limited. This study aimed to evaluate the validity of the 11-point peak pruritus numerical rating scale (PP NRS) as a single-item patient-reported outcome (PRO) measure for assessing itch severity in PN. METHODS: Content validity of the PP NRS was evaluated through qualitative interviews with adults with PN. The PP NRS was then psychometrically evaluated using data from a placebo-controlled trial of nemolizumab in adults with PN, during which patients completed the PP NRS daily. Meaningful within-patient change was estimated from the qualitative interviews and by anchor- and distribution-based analyses of trial data. RESULTS: The interview participants (N = 21) all understood the PP NRS and reported itch as their worst symptom overall. The PP NRS showed good test-retest reliability and demonstrated convergent validity and known-groups validity. PP NRS scores improved more in patients classified as "improved" on other clinical outcome measures than in those classified as "worsened/unchanged". Triangulation of the different estimates identified a 2- to 5-point decrease in PP NRS score as a meaningful within-patient change threshold. CONCLUSION: The PP NRS is a content-valid and reliable PRO measure for quantifying itch severity in adults with PN in clinical trials. TRIAL REGISTRATION NUMBER: NCT03181503.

Prurigo nodularis is a skin disease where the skin becomes inflamed and very itchy. Itching and scratching can ruin the lives of people with prurigo nodularis. For doctors to know how well treatments for prurigo nodularis are working, they need to be able measure how bad their patients' itching is. Here we tested whether a tool called the peak pruritus numeric rating scale (PP NRS) can be used to reliably measure itching in patients with prurigo nodularis. The PP NRS asks patients to rate their itch "at the worst moment during the previous 24 h" on a scale from 0 ("no itch") to 10 ("worst itch imaginable"). We interviewed 21 patients with prurigo nodularis. Overall, itch was their worst symptom. They were able to use the PP NRS with few or no problems. To further explore whether the PP NRS can be used by patients with prurigo nodularis, we also obtained data from a clinical study. In this clinical study, patients with prurigo nodularis received a drug that might one day be used to treat their disease. They completed the PP NRS daily during the time they received the drug. When we analyzed the data from the clinical study, we found that the PP NRS has the properties a tool like this needs to be useful. We also concluded that a decrease of 2­5 points on the PP NRS scale would be a meaningful improvement in itching for patients with prurigo nodularis.

The Sleep Disturbance Numerical Rating Scale: Content Validity, Psychometric Validation, and Meaningful Within-Patient Change in Prurigo Nodularis.

INTRODUCTION: Sleep is often disturbed in patients with prurigo nodularis (PN). To address the lack of validated patient-reported outcome (PRO) measures for quantifying sleep disturbance in PN, we evaluated the Sleep Disturbance Numerical Rating Scale (SD NRS) as a single-item PRO measure for quantifying sleep disturbance in PN. METHODS: Adults with PN participated in qualitative interviews, which included concept elicitation and cognitive debriefing of the SD NRS. The SD NRS was evaluated psychometrically using data from a phase 2 randomized trial in adults with PN (NCT03181503). Other PRO assessments included the Average Pruritus (AP) NRS, AP Verbal Rating Scale (VRS), peak pruritus (PP) NRS, PP VRS, and Dermatology Life Quality Index (DLQI). Reliability, validity, and responsiveness of the SD NRS were evaluated, and meaningful within-patient change was estimated from qualitative interview responses and quantitative trial data. RESULTS: All interview participants (N = 21) experienced sleep disturbance and most (95%) understood the SD NRS as intended. The SD NRS demonstrated test-retest reliability based on intra-class correlation coefficients for itch-stable participants of 0.87 for the AP VRS and 0.76 for the PP VRS. At baseline, Spearman's rank-order correlation coefficients were moderate to strong (0.3-0.8) between the SD NRS and the AP NRS, AP VRS, PP NRS, PP VRS, and DLQI. Known-groups validity was demonstrated by higher (worse) SD NRS scores in participants with worse scores on the AP NRS, AP VRS, PP VRS, and DLQI. Improvements in SD NRS scores were greater in participants classified as "improved" versus "worsened/unchanged" on the anchor PROs. A 2- to 4-point decrease on the 11-point SD NRS scale was identified as a meaningful within-patient change. CONCLUSION: The SD NRS is a well-defined, reliable, and valid PRO measure that can be used in daily practice and clinical trials to capture sleep disturbance in adults with PN.

Patients with the skin disease prurigo nodularis often sleep badly because their skin is very itchy in the evening and at night. In assessing the effectiveness of new treatments for prurigo nodularis, it is useful to know whether patients sleep better when taking them. Here, we tested whether the "Sleep Disturbance Numerical Rating Scale" (SD NRS), a tool for measuring sleep, can be used by patients with prurigo nodularis. The SD NRS asks patients to score their sleep loss during the previous night on a scale of 0 ("no sleep loss") to 10 ("I did not sleep at all"). When we interviewed 21 patients with prurigo nodularis, 19 of them had problems falling asleep and 18 of them woke up every night. Most of the patients found the SD NRS easy to use. To further explore whether the SD NRS is suitable for patients with prurigo nodularis, we also analyzed data from a European clinical study in which patients with prurigo nodularis received nemolizumab, a new treatment being developed for the disease. Patients completed the SD NRS each morning during the clinical study. We found that the SD NRS has the necessary properties to be useful for assessing sleep on a daily basis. We also determined that a 2- to 4-point decrease on the SD NRS scale would represent a meaningful improvement in sleep for patients with prurigo nodularis. We conclude that the SD NRS is a useful tool for assessing sleep in prurigo nodularis patients participating in clinical studies.

Psychometric validation of the generalized pustular psoriasis physician global assessment (GPPGA) and generalized pustular psoriasis area and severity index (GPPASI).

BACKGROUND: Generalized pustular psoriasis (GPP) is a rare and life-threatening skin disease often accompanied by systemic inflammation. There are currently no standardized or validated GPP-specific measures for assessing severity. OBJECTIVE: To evaluate the reliability, validity and responder definitions of the Generalized Pustular Psoriasis Physician Global Assessment (GPPGA) and Generalized Pustular Psoriasis Area and Severity Index (GPPASI). METHODS: The GPPGA and GPPASI were validated using outcome data from Week 1 of the Effisayil™ 1 study. The psychometric analyses performed included confirmatory factor analysis, item-to-item/item-to-total correlations, internal consistency reliability, test-retest reliability, convergent validity, known-groups validity, responsiveness analysis and responder definition analysis. RESULTS: Using data from this patient cohort (N = 53), confirmatory factor analysis demonstrated unidimensionality of the GPPGA total score (root mean square error of approximation <0.08), and GPPGA item-to-item and item-to-total correlations ranged from 0.58 to 0.90. The GPPGA total score, pustulation subscore and GPPASI total score all demonstrated good test-retest reliability (intraclass correlation coefficient: 0.70, 0.91 and 0.95 respectively), and good evidence of convergent validity. In anchor-based analyses, all three scores were able to detect changes in symptom and disease severity over time; reductions of -1.4, -2.2 and - 12.0 were suggested as clinically meaningful improvement thresholds for the GPPGA total score, GPPGA pustulation subscore and GPPASI total score respectively. Anchor-based analyses also supported the GPPASI 50 as a clinically meaningful threshold for improvement. CONCLUSIONS: Overall, our findings indicate that the GPPGA and GPPASI are valid, reliable and responsive measures for the assessment of GPP disease severity, and support their use in informing clinical endpoints in trials in GPP.