A Cochrane review [Abstract] 1 included 8 studies with a total of 1301 subjects. A total of 919 patients contributed to the results concerning exacerbations and progression of the disease at two years. Overall, 246 (19%) participants were excluded after randomisation or were lost to follow-up. Interferon significantly reduced the occurrence of exacerbations (RR 0.80, 95% CI 0.73 to 0.88) and progression of the disease (RR 0.69, 95% CI 0.55 to 0.87) two years after randomisation. If interferon-treated patients who dropped out were deemed to have progressed (worst case scenario), the significance of these effects was lost. The evolution in magnetic resonance imaging (MRI) technology in the decade in which these trials were performed and different reporting of data among trials made it impossible to perform a quantitative analysis of the MRI results. The impact of interferon therapy (and its side effects) on the quality of life was not reported in any trial.
Comment: The quality of evidence is downgraded by study quality (a critical number of patients lost to follow-up)
Primary/Secondary Keywords