At the SR Core, we are conversant with methodological standards and processes for systematic and other evidence reviews, and our goal is to help you develop a high-quality manuscript following sound methodology (Cochrane Handbook, National Academy of Medicine, Agency for Healthcare Research and Quality, Joanna Briggs Institute, OHAT) and reporting guidelines (PRISMA, MOOSE).
SR Core Services
- Question refinement
- Finding the right fit between your objectives and type of evidence review
- Methodological guidance on all aspects of systematic (and other evidence) reviewing
- Protocol Development:
- Inclusion & Exclusion Criteria
- Search methods and search process
- Data extraction—elements and process
- Statistical analysis plan (in consultation with statisticians from the Study Design and Biostatistics Center (SDBC)
- search methodology
- background information
- search plan and methodology to inform IRB applications and grants.
- Bibliographic data management
- Systematic Review Software—advice on choice and set up
- Full text retrieval of journal articles
- Identifying relevant journals for publication
Statistics for Evidence Synthesis
Meta-analysis associated with Systematic Reviews of Randomized Controlled Trials or Non-Randomized Studies is defined in the Cochrane Handbook as the “statistical combination of results from two or more separate studies.” Key points from Cochrane to consider when developing a data synthesis plan for a systematic review:
- Potential advantages of meta-analyses include an increase in power, an improvement in precision, the ability to answer questions not posed by individual studies, and the opportunity to settle controversies arising from conflicting claims. However, they also have the potential to mislead seriously, particularly if specific study designs, within-study biases, variation across studies, and reporting biases are not carefully considered.
- It is important to be familiar with the type of data (e.g. dichotomous, continuous) that result from measurement of an outcome in an individual study, and to choose suitable effect measures for comparing intervention groups.
- Most meta-analysis methods are variations on a weighted average of the effect estimates from the different studies.
- Variation across studies (heterogeneity) must be considered, although most Cochrane reviews do not have enough studies to allow the reliable investigation of the reasons for it. Random-effects meta-analyses allow for heterogeneity by assuming that underlying effects follow a normal distribution.
- Many judgements are required in the process of preparing a Cochrane review or meta-analysis. Sensitivity analyses should be used to examine whether overall findings are robust to potentially influential decisions.
- “Network meta-analysis, in the context of a systematic review, is a meta-analysis in which multiple treatments (that is, three or more) are being compared using both direct comparisons of interventions within randomized controlled trials and indirect comparisons across trials based on a common comparator.” Li et al. BMC Medicine 2011;9:79
Mary McFarland, BSc