Systematic Review:
* Explicit and Reproducible Methodology: Employs a predefined and documented search strategy, inclusion/exclusion criteria, and data extraction methods. This allows others to replicate the review and verify the findings. The methodology is transparent and clearly articulated.
* Comprehensive Search Strategy: Uses multiple databases, grey literature (e.g., conference proceedings, dissertations), and potentially hand-searching to identify all relevant studies on a specific topic. Aims for comprehensiveness and minimizes bias in study selection.
* Critical Appraisal of Studies: Includes a rigorous assessment of the quality and methodological rigor of included studies using predetermined criteria. This helps to evaluate the trustworthiness of the evidence.
* Data Extraction and Synthesis: Data from included studies are extracted systematically and often quantitatively synthesized (e.g., meta-analysis) to provide a summary of the findings. Qualitative synthesis can also be used, but it's structured and transparent.
* Bias Assessment: Explicitly assesses potential sources of bias throughout the review process, including publication bias, selection bias, and other potential confounding factors.
* Pre-defined Research Question: Starts with a clearly defined and focused research question that guides the entire process.
* Objective Reporting: Aims for an objective and unbiased summary of the evidence, minimizing the authors' interpretation.
Narrative Review:
* Implicit and Subjective Methodology: The selection of studies and the synthesis of findings are often less explicit and more subjective, relying heavily on the authors' judgment and experience. The methodology is generally less transparent.
* Limited Search Strategy: Typically uses a less comprehensive search strategy, often relying on readily available literature known to the authors. May miss important studies.
* Variable Appraisal of Studies: May include a less rigorous or even absent critical appraisal of the included studies. The quality of evidence might not be systematically assessed.
* Subjective Synthesis: Summarizes findings in a narrative form, often with a focus on the authors' interpretation and perspective. The synthesis is less structured and more interpretive.
* Limited Bias Assessment: Rarely includes explicit assessment of bias.
* Broad Research Question: Can cover a broad range of topics, often without a tightly focused research question.
* Subjective Reporting: The authors' views and perspectives significantly influence the presentation and interpretation of the findings.
In essence, a systematic review is a more rigorous and objective approach to synthesizing research evidence than a narrative review. While narrative reviews can be valuable for providing an overview of a topic or exploring emerging areas, systematic reviews offer a higher level of evidence and are considered the gold standard for informing clinical practice and policy decisions.