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.