Reliability of the gross motor function classification system and the manual ability classification system in children with cerebral palsy in Tanzania

Objectives: Gross Motor Function Classification System (GMFCS) and Manual Ability Classification System (MACS) are broadly studied in high-income countries, but data concerning their functioning are lacking in developing countries. Therefore, we analyzed their reliability and sensitivity to change in children with cerebral palsy in Tanzania. Methods: GMFCS and MACS are two ordinal grading systems used to assess motor functions while observing children’s performances. Forty-nine children were classified by two independent physiotherapy students at baseline, after one month and after one year. Reliability and sensitivity to change were analyzed using intraclass correlation coefficient (ICC), effect size (ES), standard response mean (SRM), standard error of measurement (SEM), and minimal detectable change (MDC). Results: Inter- (ICC = 0.97/0.95 for GMFCS/MACS) and intra-rater reliability (ICC = 0.98/0.96 GMFCS/MACS) were excellent. Sensitivity to change was small (ES = −0.14/0.11, SRM = −0.24;/0.24 GMFCS/MACS). SEM was 0.2 points, resulting in MDC = 0.5/0.7 for GMFCS/MACS, respectively. Conclusions: GMFCS and MACS demonstrated excellent reliability, but not sensitivity to change.