The aim of this study was to investigate the reliability and validity of the Trunk Control Measurement Scale (TCMS) among children with cerebral palsy (CP) who were living in Tanzania. Two physiotherapy trainees, each blinded to the other's test findings, independently administered the TCMS to 38 children with CP (16 female; M age = 7.2, SD = 4.8 years) twice over sessions separated by a 30-day interval. We assessed internal consistency and intra/inter-rater reliability using Cronbach's alpha and the Intraclass Correlation Coefficient (ICC), respectively. We examined measurement error through Standard Error of Measurement (SEM) and Minimal Detectable Change (MDC). We assessed construct validity with Spearman's correlation coefficient between the TCMS and both the Gross Motor Function Classification System (GMFCS) and the Manual Ability Classification System (MACS). We found a frank floor effect. Internal consistency (α = 0.945) and reliability indices were excellent for the total scale (ICC for intra-rater reliability = 0.985, inter- reliability = 0.997) and for each sub-scale score. We found low values of SEM (1.7 points) and MDC (4.8 points). Construct validity was supported by moderate and strong correlations between the TCMS and the GMFCS and MACS in this sample. We conclude that the psychometric properties of the TMCS support its clinical and research use for youth with CP in low-income settings.
Keywords: developing countries; outcome assessment; psychometrics; rehabilitation; reproducibility.