Test–retest reliability of the Test of Gross Motor Development-3 instrument for children with Down syndrome

Background The Test of Gross Motor Development-3 (TGMD-3 2019) evaluates fundamental gross motor skills across two domains: locomotor and ball skills. Objectives The purpose of this study was to determine the test–retest reliability of the TGMD-3 in children with Down syndrome. Method Twenty-four children with Down syndrome, aged 9–15 years, from five special needs schools in the North West province of South Africa participated in this study. Results Excellent and good intraclass correlation coefficient values were reported for locomotor (0.91), ball (0.84) and overall gross motor performance (0.91). Standard error of measurement, minimal detectable change at the 95% and Bland–Altman plots showed acceptable precision levels, low variability, a small discrepancy between scores for the two assessments and no systematic bias in the analyses. The test and retest values for locomotor (p = 0.587), ball (p = 0.403) and overall gross motor scores (p = 0.321) were not significant. Conclusion The TGMD-3 instrument showed good to excellent test–retest reliability for assessing gross motor skills in children with Down syndrome. Contribution This study provides an initial reliability analysis of the TGMD-3 instrument amongst selected children with Down syndrome in five districts of the North West province of South Africa.