Reliability of the dynamic gait index in people with vestibular disorders

Objective: To examine the interrater reliability of the Dynamic Gait Index (DGI) when used with patients with vestibular disorders and with previously published instructions. Design: Correlational study. Setting: Outpatient physical therapy clinic. Participants: Subjects included 30 patients (age range, 27-88y) with vestibular disorders, who were referred for vestibular rehabilitation. Interventions: Subjects' performance on the DGI was concurrently rated by 2 physical therapists experienced in vestibular rehabilitation to determine interrater reliability. Main Outcome Measures: Percentage agreement, kappa statistics, and the ratio of subject variability to total variability were calculated for individual DGI items. Kappa statistics for individual items were averaged to yield a composite kappa score of the DGI. Total DGI scores were evaluated for interrater reliability by using the Spearman rank-order correlation coefficient. Results: Interrater reliability of individual DGI items varied from poor to excellent based on kappa values (kappa range, .35-1.00). Composite kappa values showed good overall interrater reliability (kappa = .64) of total DGI scores. The Spearman rho demonstrated excellent correlation (r = .95) between total DGI scores given concurrently by the 2 raters. Conclusion: DGI total scores, administered by using the published instructions, showed moderate interrater reliability with subjects with vestibular disorders. The DGI should be used with caution in this population at this time, because of the lack of strong reliability.