Systematic Review


Systematic review is a form of structure medical literature review uses explicit methods to perform a thorough literature search and critical appeal of individual studies and that uses appropriate statistical techniques to combine these valid studies. It uses analysis of evidence, and involves objective means of searching the literature, applying predetermined inclusion and exclusion criteria to this literature, critically appraising the relevant literature, and extraction and synthesis of data from evidence base to formulate findings.

“Systematic reviews can help practitioners keep abreast of the medical literature by summarizing large bodies of evidence and helping to explain differences among studies on the same question. A systematic review involves the application of scientific strategies, in ways that limit bias, to the assembly, critical appraisal, and synthesis of all relevant studies that address a specific clinical question. A meta-analysis is a type of systematic review that uses statistical methods to combine and summarize the results of several primary studies. Because the review process itself (like any other type of research) is subject to bias, a useful review requires clear reporting of information obtained using rigorous methods. Used increasingly to inform medical decision making, plan future research agendas, and establish clinical policy, systematic reviews may strengthen the link between best research evidence and optimal health care.”

The goal of systematic review is to provide evidence-based healthcare by integrating individual clinical expertise with the best available external clinical evidence from systematic research.

Evidence Based Pyramid


Strengths and Weaknesses

While systematic reviews are regarded as the strongest form of medical evidence, a review of 300 studies found that not all systematic reviews were equally reliable, and that their reporting could be improved by a universally agreed upon set of standards and guidelines.

A further study by the same group found that of 100 guidelines reviewed, 4% required updating within a year, and 11% after 2 years; this figure was higher in rapidly-changing fields of medicine, especially cardiovascular medicine. 7% of systematic reviews needed updating at the time of publication.

Due to the overwhelming volumes of medical literature, we prefer summaries of information instead of full publications. This makes a well-conducted systematic review invaluable for practitioners. High-quality systematic reviews can define the boundaries of what is known and what is not known and can help us avoid knowing less than has been proven.

Systematic reviews can help practitioners solve specific clinical problems. It can improve our understanding of inconsistence among diverse research evidence. By integrating all the information of several studies, meta-analyses can create more precise, powerful, and convincing conclusions.

“Investigators need systematic reviews to summarize existing data, refine hypotheses, estimate sample sizes, and help define future research agendas. Without systematic reviews, researchers may miss promising leads or may embark on studies of questions that have been already answered. Administrators and purchasers need review articles and other integrative publications to help generate clinical policies that optimize outcomes using available resources.

Systematic reviews can aid, but can never replace, sound clinical reasoning. Clinicians reason about individual patients on the basis of analogy, experience, heuristics, and theory as well as research evidence. Awareness of a treatment's effectiveness does not confer knowledge about how to use that treatment in caring for individual patients. Evidence can lead to bad practice if it is applied in an uncritical or unfeeling way. Understanding the complex structure of medical decision-making requires an appreciation of the ways in which knowledge, skills, values, and research evidence are integrated in each patient-clinician encounter. “



“The Cochrane Collaboration is an international not-for-profit and independent organization, dedicated to making up-to-date, accurate information about the effects of healthcare readily available worldwide. It produces and disseminates systematic reviews of healthcare interventions and promotes the search for evidence in the form of clinical trials and other studies of interventions. The Cochrane Collaboration was founded in 1993 and named after the British epidemiologist, Archie Cochrane.

The Cochrane Collaboration consists of a group with over 6,000 specialists in health care who systematically review randomised trials of the effects of treatments and, when appropriate, the results of other research. They are known as the Cochrane Reviews Groups.

These quarterly reviews are published in the Cochrane Database of Systematic Reviews section of the The Cochrane Library.

Web Resources

Related Terminology

Cochrane Reviews
The Cochrane Library
PubMed Clinical Queries


Cook, Deborah. Mulrow, Cynthia. Haynes, Brian. (1997) Systematic Reviews: Synthesis of Best Evidence for Clinical Decisions. Retrieved on March 13, 2008 from