Reliability of the Gross Motor Function Measure-66 scale in the evaluation of children with cerebral palsy: validation for Colombia

Infantile cerebral palsy is the leading cause of physical disability in childhood and generates different alterations in motor development that prevent the child's independence. The Gross Motor Function Measure (GMFM) scale is considered the gold standard for this measurement in children with infantile cerebral palsy. In Colombia, its use is delayed due to its original language (English) and no studies on its validity in this specific field. This study aimed to determine whether cultural equivalence allows maintaining the reliability characteristics of the instrument to favor its use in the clinical setting. We conducted a cross-sectional study that included 330 children with infantile cerebral palsy from three departments of Colombia, to whom the GMFM-66 scale was applied. Reliability was evaluated from interobserver consistency by estimating intraclass correlation coefficients and internal consistency with the omega coefficient (w) or McDonald's test. The scale demonstrates consistency and stability in its measurements in terms of reliability. The internal consistency was satisfactory only for the first dimension, Lying and rolling (w = 0.91). For the other dimensions, the w-value was always > 0.95. Good agreement was found among the experts in 83.3% of the items and dimensions evaluated. The GMFM-66 scale in Spanish and for the Colombian context demonstrates good psychometric properties and provides a better understanding of the motor development of children with infantile cerebral palsy so that it can be recommended for use in the Colombian context.