Stability of the Gross Motor Function Classification System in adults with cerebral palsy.

To determine the stability of Gross Motor Function Classification System (GMFCS) levels between approximately 12 years of age and adulthood (i.e. > 16y) using a matched chart review. Adult health records from the Ottawa Rehabilitation Centre were matched with childhood health records from the Ottawa Children's Treatment Centre (OCTC). Health records were available for 103 adults (52 males, 51 females) with cerebral palsy (CP; age range 17-38y; mean age 22y [SD 4y]) who had also been seen at the OCTC at a mean age of 12 years (SD 1y). GMFCS levels as adults were: Level I, n= 10; Level II, n= 24; Level III, n= 21; Level IV, n= 30; and Level V, n= 18. Adult participants were classified using the GMFCS at the time they were last seen by a rehabilitation specialist, sometime between June 2002 and June 2005. Corresponding paediatric charts were reviewed and classified by two independent raters blinded to the adult GMFCS levels. GMFCS levels around age 12 were: Level I, n= 20; Level II, n= 13; Level III, n= 22; Level IV, n= 35; and Level V, n= 13. Interrater reliability for childhood health records was determined with a quadratic weighted kappa and was 0.978. Stability of GMFCS levels was also assessed using the quadratic weighted kappa and was 0.895. The positive predictive value of the GMFCS at 12 years of age to predict walking without mobility aids by adulthood is 0.88. If the child is a wheelchair user at around age 12 years, the positive predictive value is 0.96 that the individual will still be a wheelchair user as an adult. This study supports previous findings that interrater reliability when using the GMFCS is very high. It also shows that the GMFCS level observed around the age of 12 years is highly predictive of adult motor function. This provides important information for individuals with CP, their families, and care providers as they plan for future care needs and rehabilitation intervention.