The Pediatric Quality of Life Inventory 3.2 Diabetes Module: Preliminary Validation and Initial Evidence of Reliability and Factor Structure of the Croatian Version

Background/Objectives: Type 1 diabetes mellitus (T1DM) in primary school children presents unique challenges due to developmental dependence on adults, limited self-care abilities, and the need for continuous medical supervision. These factors may adversely affect health-related quality of life (HRQoL), particularly in early educational settings. Although diabetes-specific HRQoL assessment is essential for comprehensive pediatric diabetes care, no validated Croatian language instrument has previously been available. This preliminary study aimed to evaluate the initial validity, reliability, and factor structure of the Croatian version of the Pediatric Quality of Life Inventory (PedsQL) 3.2 Diabetes Module. Methods: This cross-sectional preliminary study was conducted in a clinical pediatric diabetes care setting in Croatia and included 70 children with T1DM, aged 7–14 years, and their parents or caregivers, recruited using convenience sampling. HRQoL was assessed using the Croatian versions of the PedsQL 4.0 Generic Core Scales and the PedsQL 3.2 Diabetes Module, which was translated using a forward-backward translation procedure. Reliability was evaluated using Cronbach’s α and test–retest reliability using the intraclass correlation coefficient (ICC). Construct validity was examined using Spearman’s correlation analysis and exploratory factor analysis. Results: Children with T1DM reported higher overall HRQoL than parent proxy reports, except for the Diabetes symptoms scale of the PedsQL 3.2 Diabetes Module and the School functioning scale of the PedsQL 4.0 Generic Core Scales. Internal consistency was satisfactory across all scales (Cronbach’s α = 0.71–0.85). Spearman’s correlations between subscales and total scores were strong (ρ = 0.61–0.92). Test–retest reliability was excellent (ICC = 0.982–0.996). Exploratory factor analysis supported construct validity: Bartlett’s test of sphericity was significant for both child (χ2 = 1398.57, p < 0.001) and parent reports (χ2 = 1302.74, p < 0.001), and the Kaiser–Meyer–Olkin measure indicated acceptable sampling adequacy (child = 0.65; parent = 0.68). Extracted factors explained 66.30% of the variance in child reports and 61.80% in parent reports, with factor loadings ranging from 0.41 to 0.89 and 0.41 to 0.85, respectively. Conclusions: The Croatian version of the PedsQL 3.2 Diabetes Module is an initial valid, reliable, and feasible instrument for assessing diabetes-specific HRQoL in Croatian primary school children with T1DM. Its use may support systematic HRQoL monitoring and improve family-centered pediatric diabetes care.