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.