MS-SMART study: systematic sampling bias concerns

摘要

We read the results of the MS-SMART trial reported by Jeremy Chataway and colleagues in The Lancet Neurology comparing the efficacy of three neuro-protective drugs in secondary progressive multiple sclerosis. We noted that they did not find evidence of neuroprotective efficacy for the three therapeutics under investigation. Although we applaud the researchers' investigation of drug repurposing in multiple sclerosis, especially in association with neuroprotective mechanisms in secondary progressive multiple sclerosis, for which therapeutics are much needed, we would like to highlight two essential points. First, the authors have not specified the reasons for exclusion of ineligible participants. The Article reports that 547 people with multiple sclerosis were screened for eligibility and 102 were excluded, with 90 of 102 reported as ineligible without further details. Second, participants with multiple sclerosis who reported moderate-to-severe depressive symptoms were excluded, which is likely to create a systematic sampling bias and might contribute to a false negative result—an issue we have previously highlighted with reporting of the FLUOX-PMS study.