title: Interobserver agreement of the Gross Motor Function Classification System in an ambulant population of children with cerebral palsy.
abstract: Gross Motor Function Classification System (GMFCS) level was reported by three independent assessors in a population of children with cerebral palsy (CP) aged between 4 and 18 years (n=184; 112 males, 72 females; mean age 10y 10mo [SD 3y 7mo]). A software algorithm also provided a computed GMFCS level from a regional CP registry. Participants had clinical diagnoses of unilateral (n=94) and bilateral (n=84) spastic CP, ataxia (n=4), dyskinesia (n=1), and hypotonia (n=1), and could walk independently with or without the use of an aid (GMFCS Levels I-IV). Research physiotherapist (n=184) and parent/guardian data (n=178) were collected in a research environment. Data from the child's community physiotherapist (n=143) were obtained by postal questionnaire. Results, using the kappa statistic with linear weighting (kappa(1w)), showed good agreement between the parent/guardian and research physiotherapist (kappa(1w)=0.75) with more moderate levels of agreement between the clinical physiotherapist and researcher (kappa(1w)=0.64) and the clinical physiotherapist and parent/guardian (kappa(1w)=0.57). Agreement was consistently better for older children (>2y). This study has shown that agreement with parent report increases with therapists'experience of the GMFCS and knowledge of the child at the time of grading. Substantial agreement between a computed GMFCS and an experienced therapist (kappa(1w)=0.74) also demonstrates the potential for extrapolation of GMFCS rating from an existing CP registry, providing the latter has sufficient data on locomotor ability.
authors.affiliation: Gait Analysis Laboratory, Musgrave Park Hospital, Stockman's Lane, Belfast, UK. brona.mcdowell@belfasttrust.hscni.net
authors.forename: Brona C
authors.initials: BC
authors.lastname: McDowell
authors.forename: Claire
authors.initials: C
authors.lastname: Kerr
authors.forename: Jackie
authors.initials: J
authors.lastname: Parkes
mesh_terms: D000293:Adolescent; D000367:Age Factors; D002547:Cerebral Palsy / Q000145:classification* / Q000503:physiopathology*; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D051341:Dependent Ambulation; D004185:Disability Evaluation; D005190:Family / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D009048:Motor Skills / Q000502:physiology*; D015588:Observer Variation; D026761:Physical Therapy Specialty / Q000706:statistics & numerical data; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires