Guidelines for reporting meta-epidemiological methodology research.

Published research should be reported to evidence users with clarity and transparency that facilitate optimal appraisal and use of evidence and allow replication by other researchers. Guidelines for such reporting are available for several types of studies but not for meta-epidemiological methodology studies. Meta-epidemiological studies adopt a systematic review or meta-analysis approach to examine the impact of certain characteristics of clinical studies on the observed effect and provide empirical evidence for hypothesised associations. The unit of analysis in meta-epidemiological studies is a study, not a patient. The outcomes of meta-epidemiological studies are usually not clinical outcomes. In this guideline, we adapt items from the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) to fit the context of meta-epidemiological studies.