Purpose: The study evaluated the ability of each item of the Test of Infant Motor Performance to separate children into developmental outcome groups.
Subjects: Ninety-six infants with typical development (n = 67), cerebral palsy (n = 10) or developmental delay (n = 8) participated.
Methods: A retrospective study was conducted using an existing Test of Infant Motor Performance data set. Discriminant analyses of items' rates of change at eight and 13 weeks' corrected age (independent variables) and outcome groups (dependent variables) were run.
Results: Data obtained at eight weeks' corrected age showed better discrimination and predictive validity than at 13 weeks' corrected age. Item rates and directions of change combined differently to maximize the separation among outcome groups depending on age.
Discussion/Conclusion: Motor behaviors that could identify cerebral palsy might differ with age, depending on (1) the stage of brain and body development, and (2) whether the motor ability level itself or the speed with which children acquire different motor skills is being evaluated.