Missing data

This paper raises a practical concern: how can we avoid a situation in which a randomized controlled trial (RCT) shows that a therapy has a statistically significant and clinically important benefit for amyotrophic lateral sclerosis (ALS) patients, but the credibility of the result is called into question because of missing data? This is a real possibility, and potentially a very serious problem for ALS investigators. It is the responsibility of statisticians and others to recommend steps to minimize it. In this paper we emphasize the importance of missing data in RCTs, and discuss how the problem can be handled in an unbiased way by imputation procedures. We then summarize the limitations of these imputation procedures, and conclude with some recommendations for trial design and conduct that are tailored to RCTs for ALS.

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