Instrument for the Assessment of Dynamic Postures in Children and Adolescents (DAP-CA): Development, Content Validity, Reliability, and Sensitivity to Pre–Post Change

Abstract Postural changes in children and adolescents are often associated with less optimal postural patterns during activities of daily living; therefore, valid, reliable, and responsive tools are needed to analyze dynamic posture in different contexts. This study developed and validated an instrument to assess the dynamic posture of children and adolescents during postural habits in activities of daily living, using video observation and applicable both in person and online. A methodological study conducted in two stages: instrument development and evaluation of its psychometric properties. First stage: (A) Literature review; (B) Field research; and (C) Development of the initial version. Second stage: (D) Content validation was performed with the Content Validity Index (CVI) by an expert panel; (E) Inter-rater reliability was performed for each biomechanical criterion of dynamic postures in the DAP-CA, measured by Fleiss’ Kappa coefficient (FKC), and intra-rater reliability was assessed by Kappa Coefficient (KC). The reliability of the overall DAP-CA score was analyzed using the Intraclass Correlation Coefficient (ICC) and also the Standard Error of Measurement (SEM) and the Minimal Detectable Change (MDC); and (F) sensitivity to pre–post change was evaluated before and after intervention using Student’s t-test (p≤0.05), Effect Size (ES), and Standardized Response Mean (SRM). The DAP-CA showed high content validity (CVI ≥ 0.90) and was considered applicable by experts. Inter-rater reliability ranged from substantial to almost perfect, and intra-rater reliability ranged from substantial to almost perfect, across both in-person and online modalities. The overall score demonstrated good to excellent reliability across the face-to-face and online modalities (ICC = 0.89–0.94), with SEM values ranging from 0.46 to 0.62 points and MDC values ranging from 1.27 to 1.72 points. The DAP-CA detected significant pre- to post-intervention changes (p<0.001), with large standardized effect sizes and standardized response means. The DAP-CA demonstrated evidence of content validity, substantial to almost perfect inter- and intra-rater agreement, and good to excellent reliability of the overall score. It also demonstrated sensitivity to pre- to post-intervention changes, supporting its potential use for assessing dynamic posture in children and adolescents.