Problems in evaluating new treatments for multiple sclerosis.

There are multiple difficulties in evaluating new treatments for multiple sclerosis (MS). The clinical diagnosis is imprecise, and the correlation between lesion and clinical dysfunction is incomplete. The neurologic evaluation is complex and lacks full precision. The course of MS is complex and has limited predictability. There is no laboratory test that can be accepted now as compensating for the defects in diagnosis, lesion-symptom correlation, course, and neurologic evaluation. Because of these problems, which appear inherent in MS, there are limitations to the statistical methods that can be properly applied to trials of therapy. Most trials of definitive nature will require a random design. When improvement is seen in a trial of therapy, there may be difficulty in determining the mechanism.