The Turkish adaptation of the Child Occupational Self-Assessment Scale (COSA) and its psychometric properties in children with attention-deficit/hyperactivity disorder

Occupational therapy practices are expanding in Turkey; however, pediatric professionals lack validated, client-centered assessment instruments for children with attention-deficit/hyperactivity disorder (ADHD). This study aimed to adapt the Child Occupational Self-Assessment (COSA) version 2.2 into Turkish (COSA-TR) and evaluate its psychometric properties using both Classical Test Theory (CTT) and Rasch Measurement Theory. A total of 101 children (aged 7–11) diagnosed with ADHD participated in this cross-cultural adaptation study. Construct validity was examined using Principal Component Analysis (PCA) with Varimax rotation and Rasch analysis (Partial Credit Model). Item–person targeting was assessed via a Wright Map, and internal structural integrity was evaluated using Infit and Outfit Mean Square (MNSQ) statistics. The functioning of the 4-point rating scale was verified through category probability curves and threshold ordering analysis. Discriminant validity was assessed through inter-subscale correlations, while criterion validity was evaluated via concurrent correlation with the Short Child Occupational Profile (SCOPE). Reliability was examined using Cronbach’s alpha with bootstrap resampling (1,000 iterations) and Weighted Likelihood Estimates (WLE), including person/item separation indices and strata. PCA identified a statistically robust seven-factor structure (communication skills, executive functions, motor functions, school participation, self-regulation, instrumental activities of daily living (IADL), and activities of daily living (ADL)), explaining 69.74% of the total variance. Rasch analysis confirmed an excellent model-data fit, with 100% of items meeting Infit MNSQ criteria (0.50–1.50). The Wright Map demonstrated good alignment between item difficulty and child competence (Mean person ability: -0.50 logits). The 4-point Likert scale showed functional monotonic threshold ordering. Criterion validity was supported by a significant correlation with SCOPE (r = .675, p < .001). Total scale reliability was high (α = 0.862; WLE = 0.841). Person separation indices (2.30) and strata (3.40) indicated that the instrument can effectively distinguish between statistically distinct competence levels. The COSA-TR is a valid and reliable client-centered instrument for assessing occupational competence and importance in Turkish children with ADHD. Its integration of CTT and Rasch-based evidence provides a rigorous foundation for clinical goal-setting and outcomes measurement in pediatric occupational therapy.