Predictive validity and responsiveness of the Functional Ambulation Category in hemiparetic patients after stroke

Objective: To determine the reliability, concurrent and predictive validity, and responsiveness of the Functional Ambulation Category (FAC) in hemiparetic patients after stroke. Design: Prospective cohort. Setting: An early rehabilitation center for patients with neurologic disorders. Participants: Fifty-five nonambulatory patients after first-ever stroke, with duration of illness between 30 and 60 days, were included. Interventions: Not applicable. Main Outcome Measures: FAC, Rivermead Mobility Index (RMI), walking velocity, step length, and six-minute walking test (6MWT) were assessed at the beginning, after 2 and 4 weeks of rehabilitation, and again 6 months later. After 6 months, community ambulation was also assessed. Test-retest and interrater reliability, concurrent, discriminant, and predictive validity and responsiveness of the FAC were calculated. Results: Based on video examinations, high test-retest reliability (Cohen kappa=.950) and interrater reliability (kappa=.905) were found. FAC scores at the beginning and after 2 weeks, 3 weeks, and 6 months correlated highly with the RMI (Spearman rho=.686, rho=.787, rho=.825, rho=.893, respectively), distance walked in the 6MWT (rho=.949, rho=.937, rho=.931, rho=.906, respectively), walking velocity (rho=.952, rho=.939, rho=.902, rho=.901, respectively), and step length (rho=.952, rho=.932, rho=.896, rho=.877, respectively) at the same time points (all P<.001). The RMI, walking velocity, step length, and distance walked in the 6MWT differed for each FAC category (P<.001). After 4 weeks of rehabilitation, an FAC score of 4 or higher predicted community ambulation at 6 months with 100% sensitivity and 78% specificity. FAC scores changed significantly between the first 2 and second 2 weeks (Wilcoxon z = 8.7, z = 7.9, respectively; both P<.001) of the inpatient rehabilitation program. Conclusions: The FAC has excellent reliability, good concurrent and predictive validity, and good responsiveness in patients with hemiparesis after stroke.