Predictive Validity and Responsiveness of the Functional Ambulation Category in Hemiparetic Patients After Stroke

Abstract

Mehrholz J, Wagner K, Rutte K, Meiβner D, Pohl M. 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 κ=.950) and interrater reliability (κ=.905) were found. FAC scores at the beginning and after 2 weeks, 3 weeks, and 6 months correlated highly with the RMI (Spearman ρ=.686, ρ=.787, ρ=.825, ρ=.893, respectively), distance walked in the 6MWT (ρ=.949, ρ=.937, ρ=.931, ρ=.906, respectively), walking velocity (ρ=.952, ρ=.939, ρ=.902, ρ=.901, respectively), and step length (ρ=.952, ρ=.932, ρ=.896, ρ=.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.