Test of gross motor development-2 for Filipino children with intellectual disability: validity and reliability

This study aimed to examine aspects of validity and reliability of the Test of Gross Motor Development-2 (TGMD-2) in Filipino children with intellectual disability. Content and construct validity were verified, as well as inter-rater and intra-rater reliability. Two paediatric physiotherapists tested 81 children with intellectual disability (mean age = 9.29 ± 2.71 years) on locomotor and object control skills. Analysis of covariance, confirmatory factor analysis and analysis of variance were used to test validity, while Cronbach's alpha, intra-class correlation coefficients (ICC) and Bland-Altman plots were used to examine reliability. Age was a significant predictor of locomotor and object control scores (P = 0.004). The data fit the hypothesised two-factor model with fit indices as follows: χ(2) = 33.525, DF = 34, P = 0.491, χ(2)/DF = 0.986. As hypothesised, gender was a significant predictor for object control skills (P = 0.038). Participants' mean scores were significantly below mastery (locomotor, P < 0.001; object control, P < 0.001). Cronbach's alpha was 0.830 for locomotor and 0.792 for object control components. ICC for locomotor and object control scores ranged from 0.995 to 0.998, suggesting excellent intra-rater and inter-rater reliability, confirmed by Bland-Altman analysis. This study provides evidence of sufficient content and construct validity, internal consistency and rater reliability of TGMD-2 for Filipino children with intellectual disability.