A Systematic Review is a scientific method used to collect, evaluate, and analyze multiple studies discussing the same medical question, treatment, phenomenon, or scientific issue in order to reach stronger and more reliable conclusions based on the combined evidence. In general, before conducting a Systematic Review, there should be at least three studies available that investigate the same topic using relatively similar methodologies and reporting comparable outcomes. Without sufficient studies, it becomes difficult to perform a meaningful scientific synthesis or produce reliable conclusions.
A Systematic Review can be applied to different study designs, including single-arm studies as well as two-arm comparative studies such as Randomized Controlled Trials (RCTs), prospective cohort studies, retrospective cohort studies, and other appropriate analytical designs. However, the included studies should share similar methodologies, comparable populations, similar interventions or exposures, and closely related outcomes to ensure that the scientific comparison remains valid and meaningful.
An important requirement before starting a Systematic Review is ensuring that the idea itself has not already been published previously as a completed Systematic Review and that no published protocol already exists for the exact same research question. Researchers must therefore carefully search databases and protocol registries such as PROSPERO to confirm that the project is novel and not duplicated. This step is extremely important to avoid repetition, reduce publication redundancy, and ensure that the review contributes new scientific value to the literature.
The general concept of a Systematic Review is that researchers identify several studies investigating the same scientific question — for example, the effect of a specific drug, the outcome of a surgical procedure, the association between a risk factor and a disease, or a particular medical phenomenon. Although these studies may produce different or even conflicting results, they often use similar methodologies and evaluate related outcomes. Researchers then systematically collect and analyze all eligible studies together in order to generate stronger evidence, obtain more precise estimates, and potentially contribute to clinical guidelines, medical recommendations, and evidence-based decision-making.
In many cases, combining studies through Systematic Reviews and Meta-Analyses allows scientists to better understand the true effectiveness, safety, risks, and clinical impact of treatments or interventions compared to relying on a single study alone.
Importance of Systematic Review and Meta-Analysis
Types of Systematic Reviews and Meta-Analyses
This type evaluates the effectiveness and safety of treatments or interventions by comparing therapies, medications, procedures, or healthcare strategies.
Examples