Deficiencies in addressing effect modification in network meta-analyses: a meta-epidemiological survey

OBJECTIVE: The objectives of this study were to evaluate the current state of reporting and handling of effect modification in network meta-analyses (NMAs) and perform exploratory analyses to identify variables that are potentially associated with incomplete reporting of effect modifiers in NMAs. STUDY DESIGN AND SETTING: We conducted a meta-epidemiological survey using a systematic review of NMAs published in 2013 and identified through MEDLINE and Embase databases. RESULTS: The review identified 77 NMAs. The most common type of effect modifiers identified and explored were patient characteristics (50.7% or 39/77), and the most common adjustment method used was sensitivity analysis (51.7% or 30/58). Over 45% (35/77) of studies did not describe a plan, nearly 40% (30/77) did not report the results of analyses, and approximately 47% (36/77) of studies had incomplete reporting. Exploratory univariate regression analyses yielded a statistically significant association for the variables of journal impact factor, ratio of randomized controlled trials to number of comparisons, and total number of randomized controlled trials. CONCLUSION: Current reporting practices are largely deficient, given that almost half of identified published NMAs do not explore or report effect modification. Journal impact factor and amount of available information in a network were associated with completeness of reporting.