Meta-analysis methods focus on contrasting and comparing results from different studies in anticipation of identifying consistent patterns and sources of disagreements among these results.

Primary objective

In summarizing the results and facilitating their analysis,

1. Key variables that characterize are:
• Participants
• Interventions
• Outcomes
• Internal validity of each study
2. Results in natural units that are easily understood
3. Standardized results, if these can be derived in a way that will facilitate comparisons across studies without being misleading.

Synthesis of data

Absolute measures can be more informative than relative measures because they reflect the baseline risk as well as the change in risk with the intervention.

Absolute measures are useful for presenting results, but not for analysis
purposes.

Statistical models for calculating overall effects

Perform sensitivity and subgroup analyses if appropriate and possible. Subgroups should be pre-specified to avoid bias.

Perform a narrative, qualitative summary when data are too sparse, of too low quality or too heterogeneous to proceed with a meta-analysis.

Marjan Akbari Kamrani

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