Long-term and short-term outcome of multiple sclerosis: A 3-year follow-up study

Background: The anticipated rate of short-term worsening of disability scores is the basis of power estimations in clinical trials of progressive multiple sclerosis (MS). While the clinician is most concerned in modifying the long-term outcome (eg, time to reach the Expanded Disability Status Scale [EDSS] 6), the end points studied in clinical trials are those describing short-term outcome (eg, worsening of EDSS scores over 1 to 3 years). However, short-term outcome of MS may not be correlated with long-term outcome. Objectives: To validate previously published models predicting time to EDSS 6. To establish predictors of short-term outcome of MS. Setting: The Ottawa, Ontario, Regional Multiple Sclerosis Clinic. Patients: Two hundred fifty-nine patients were followed up prospectively by a single neurologist. Main Outcome Measures: Actuarial analysis of time to reach EDSS 6 and change in EDSS scores over a follow-up period of 1 to 3 years. Results: The long-term outcome in the Ottawa population was more favorable than published data from London, Ontario. Predictions of time to EDSS 6 were not strongly correlated with the degree of short-term worsening over the follow-up period. Parameters associated with a higher probability of short-term worsening were proximity of the baseline EDSS score to 4.5 and duration of MS less than 20 years. Conclusion: Baseline EDSS and duration of MS must be considered in the design of clinical trials of progressive MS.