Systematic reviews do not adequately report or address missing outcome data in their analyses: a methodological survey

Objectives: To describe how systematic review authors report and address categories of participants with potential missing outcome data of trial participants. Study Design and Setting: Methodological survey of systematic reviews reporting a group-level meta-analysis. Results: We included a random sample of 50 Cochrane and 50 non-Cochrane systematic reviews. Of these, 25 reported in their methods section a plan to consider at least one of the 10 categories of missing outcome data; 42 reported in their results, data for at least one category of missing data. The most reported category in the methods and results sections was unexplained loss to follow-up (n = 34 in methods section and n = 6 in the results section). Only 19 reported a method to handle missing data in their primary analyses, which was most often complete case analysis. Few reviews (n = 9) reported in the methods section conducting sensitivity analysis to judge risk of bias associated with missing outcome data at the level of the meta-analysis; and only five of them presented the results of these analyses in the results section. Conclusion: Most systematic reviews do not explicitly report sufficient information on categories of trial participants with potential missing outcome data or address missing data in their primary analyses. (C) 2018 Elsevier Inc. All rights reserved.