Development and Validation of the Visual Medical Scale to Evaluate Nail Psoriasis Severity (ViSENPsO®).

INTRODUCTION: A reliable, well-defined measure of fingernail psoriasis severity for clinical trials is an unmet need. The objective of this study was to develop and validate the Visual Medical Scale to Evaluate Nail Psoriasis Severity (ViSENPsO), an illustrated 5-point tool for assessing nail psoriasis severity. METHODS: A global panel of dermatologists participated in concept elicitation (CE) interviews exploring experiences with nail psoriasis, severity markers, and biologic treatment. Participants sorted and ranked histopathology-verified photographs to refine severity categories. Follow-up cognitive interviews assessed the scale's usability and content validity, alongside a preliminary test of interrater reliability (IRR). Dermatologists' assessments were analyzed using thematic analysis to generate qualitative insights. RESULTS: s, 0.60 and 0.81). Cognitive interviews validated category definitions and visual layout. Preliminary IRR for photo rating was 0.74 (95% confidence interval, 0.34-0.84). CONCLUSION: ViSENPsO is a validated, visually guided tool for assessing standardized nail psoriasis severity. Preliminary interrater agreement was observed; comprehensive psychometric validation, including full IRR and sensitivity to change, is ongoing.