Use of the FIM instrument in a trial of intramuscular interferon beta-1a for disease progression in relapsing-remitting multiple sclerosis.

Objective: This study is a secondary analysis of results from the Multiple Sclerosis Collaborative Research Group multicenter trial. We investigated the effect of interferon beta-1a on disability in patients with relapsing-remitting multiple sclerosis (MS), using the FIM instrument to assess levels of decline in total, motor, and cognitive items.

Design: Of the 301 patients enrolled in the trial, 274 subjects with relapsing-remitting multiple sclerosis with baseline FIM and Kurtzke Expanded Disability Status Scale scores were studied in this secondary analysis. Mildly disabled patients were chosen, as indicated by a Kurtzke Expanded Disability Status Scale score of 1.0-3.5. Matched subjects were assigned to receive either interferon beta-1a or placebo. Kurtzke Expanded Disability Status Scale and FIM scores were measured serially every 6 mo. Failure was defined as a 4-point reduction in total FIM score sustained for 6 mo. Analysis was by Kaplan-Meier methodology. The Mann-Whitney test (log rank) compared mean change and Spearman's rank-correlation test determined correlation.

Result: A significant difference in treatment groups was seen, with a FIM score decline of > or = 4 points, with placebo subjects demonstrating greater loss of function than subjects treated with interferon beta-1a. There was no statistically significant difference in total, cognitive, or motor activities, with a decline of < or = 3 points.

Conclusion: Disability, as measured by the FIM instrument, was slowed by treatment with interferon beta-1a compared with placebo. The treatment effect determined using the FIM instrument, with its motor and cognitive components, indicates an additional level of response to therapy for mild to moderate multiple sclerosis.