In evidence-based medicine, systematic reviews and meta-analyses are often mentioned together but they are not the same thing. Think of them as two related steps in understanding research evidence.
A systematic review is a structured, methodical summary of all available original research on a specific question.
It involves:
- A clearly defined research question (PICO[TS])
- Comprehensive literature search
- Predefined inclusion and exclusion criteria
- Critical appraisal of study quality
- Qualitative synthesis of findings
The primary goal is to answer what the evidence says and how reliable it is.
A systematic review may exist with or without a meta-analysis.
A meta-analysis is the statistical part of a systematic review.
It involves:
- Combining numerical data from multiple studies
- Calculating pooled effect sizes
- Presenting results using forest plots
- Improving statistical power and precision
The goal is to answer how strong the effect is using numbers.
A meta-analysis cannot exist alone, it must be based on a systematic review.
The key difference is,
Systematic review => Structured search + critical evaluation
Meta-analysis => Statistical combination of results
All meta-analyses are part of systematic reviews, but not all systematic reviews include a meta-analysis.
Understanding this distinction helps one to:
- Interpret evidence correctly
- Avoid confusing narrative summaries with pooled statistics
- Choose the right method for research and publications
Systematic review builds the evidence story whereas Meta-analysis adds numerical strength to that story.
MBH/AB