Multiplicity of data in trial reports and the reliability of meta-analyses: empirical study

Ref ID 468
First Author B. Tendal
Journal BMJ
Year Of Publishing 2011
URL https://www.bmj.com/content/bmj/343/bmj.d4829.full.pdf
Keywords Cochrane
Multiplicity
General medical
Problem(s) Multiplicity of outcomes and lack of pre-specification for outcome reporting
Weaknesses identified in some Cochrane reviews
Number of systematic reviews included 19
Summary of Findings Review protocols often lacked information about which data to choose. There was multiplicity of data in at least one trial report. 29% trials reported data for multiple intervention groups, 36% reported data for multiple time points, and 35% reported the index outcome measured on multiple scales. The impact of multiple data in trial reports regarding intervention groups, time points, or measurement scales on meta-analysis results varied greatly across meta-analyses, ranging from almost no effect (0.04 standard deviation units) to a substantial one (0.91 standard deviation) units, corresponding to a large treatment effect.
Did the article find that the problem(s) led to qualitative changes in interpretation of the results? Yes
Are the methods of the article described in enough detail to replicate the study? Yes