Pilot validation of the genital psoriasis reported outcomes questionnaire in an Italian cohort.

BACKGROUND: Genital psoriasis is a highly impactful but frequently under-recognized manifestation of psoriasis, associated with pain, burning, pruritus, and substantial impairment in sexual, relational, and emotional wellbeing. Existing patient-reported outcome measures (PROMs), such as the Genital Psoriasis Symptoms Scale (GPSS) and the Genital Psoriasis Sexual Frequency Questionnaire (GenPs-SFQ), evaluate isolated domains (physical symptoms or sexual functioning) and do not provide a multidimensional assessment of the specific burden associated with genital psoriasis. To address this gap, the Genital Psoriasis Reported Outcomes (GPRO) questionnaire was developed. This study represents the first pilot psychometric validation of the GPRO questionnaire in an Italian cohort. OBJECTIVE: The study aimed to assess the feasibility, internal consistency, construct validity, structural validity, and responsiveness of the GPRO questionnaire in adult patients with genital psoriasis initiating systemic therapy. METHODS: A monocentric, prospective, observational pilot study was conducted, enrolling 57 adults with clinically confirmed genital psoriasis. Assessments were performed at baseline (T0) and at week 16 (T1). Participants completed the GPRO questionnaire, GPSS, and GenPs-SFQ, and clinicians assessed disease severity using the modified version of the Physician's Global Assessment of Genitalia (gPGA) and the Psoriasis Area and Severity Index (PASI). Analyses adhered to COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) guidance and included assessments of internal consistency (Cronbach's α), exploratory factor analysis (EFA), convergent/discriminant validity (Pearson correlations), responsiveness (ΔGPRO, ΔgPGA, and anchor-based analysis), and receiver operating characteristic (ROC) curve analysis to determine the minimal important change (MIC). RESULTS: The GPRO questionnaire showed excellent internal consistency (α = 0.94). The EFA supported a unidimensional structure, indicating a common latent construct that captures the global burden of genital psoriasis. At T0, the GPRO questionnaire demonstrated strong convergent validity, correlating with the gPGA (r = 0.77), GPSS (r = 0.54), and GenPs-SFQ domains (r = 0.7). This confirms the GPRO's capability to integrate physical and psychosocial impacts. The questionnaire showed robust responsiveness: GPRO scores significantly decreased after treatment (p < 0.001), and ΔGPRO moderately correlated with ΔgPGA (r = 0.52). The ROC analysis demonstrated good discriminative ability for detecting clinical improvement (AUC = 0.81). CONCLUSION: The GPRO questionnaire demonstrated strong preliminary psychometric performance, including internal consistency, construct validity, and responsiveness. As a multidimensional PROM, it captures different aspects of genital psoriasis. These findings support the feasibility of the GPRO questionnaire and justify further evaluation in larger multicentric studies for full validation.