To the Editor.
—Jacobs et al (Archives 1982;39:609-615) reported a "randomized, controlled trial" of interferon in multiple sclerosis (MS), in which "the most striking observation... was the dramatic reduction in exacerbations that occurred in recipients but not in controls." As the authors themselves noted, the mean exacerbation rate before the trial was higher for the ten recipients than for the ten controls (1.8/yr v 0.68/yr, respectively, for the total prestudy duration and 1.9/yr v 0.75/yr for the prestudy duration that was equal to the length of time patients had been in the study and immediately preceded their entrance into the study).Exacerbations in MS occur in an apparently random fashion with a mean frequency of 0.5/yr.1 It follows that if a small group of patients with spuriously high exacerbation rates are selected (randomly or otherwise) and studied during a subsequent period, its mean exacerbation rate will decrease, tending to
Murray N, Steck AJ. Interferon. Arch Neurol. 1983;40(6):391. doi:10.1001/archneur.1983.04050060091023
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