Development and Rasch Validation of the Parental Topical Corticosteroid Phobia Scale (PTCPS) in Pediatric Eczema Care

<b>Background and Objectives</b>: Parental fears and misconceptions about topical corticosteroids (TCS), known as TCS phobia, can hinder adherence and lead to poor eczema control in children. Despite its clinical relevance, few instruments capture this phenomenon using modern psychometric principles. This study aimed to develop and validate the Parental Topical Corticosteroid Phobia Scale (PTCPS), a brief tool grounded in Rasch measurement theory. <b>Methods</b>: A cross-sectional survey was conducted among 678 parents of children with eczema in Saudi Arabia. The five-item PTCPS was designed to reflect cognitive, emotional, and behavioral components of corticosteroid phobia. Rasch analysis using WINSTEPS assessed item fit, person and item separation and reliability, unidimensionality, and category functioning. Exploratory factor analysis (EFA) and principal component analysis (PCA) of residuals further evaluated structural validity. <b>Results</b>: All five items fit the Rasch model well (infit/outfit MnSq: 0.8-1.2), with strong item reliability (0.96) and clear item separation (4.67), indicating a well-defined item hierarchy. Person reliability was lower (0.40), suggesting limited precision in distinguishing between respondent levels. The scale showed functioning dichotomous response categories with no disordered thresholds. The eigenvalue of the first residual contrast (1.78) supported unidimensionality. Exploratory factor analysis confirmed a single-factor solution accounting for 53.0% of total variance, with substantial factor loadings (0.68-0.76) across all items, supporting structural coherence of the scale. <b>Conclusions</b>: The PTCPS is a psychometrically robust, unidimensional instrument for assessing TCS phobia in parents. Future research should validate its use across cultures, explore longitudinal stability, and assess its predictive value for treatment adherence.