Stability of the Gross Motor Function Classification System, Manual Ability Classification System, and Communication Function Classification System.

The findings support repeated classification of children over time. Stability was higher for the Gross Motor Function Classification System than the Manual Ability Classification System and Communication Function Classification System. The function of younger children was more likely to be reclassified. Percentage agreement between parents and therapists using consensus classification varied from 92% to 97%. The intraclass correlation coefficient overestimated stability compared with the weighted kappa coefficient.