Systematic reviews

What is a Systematic Review?

Systematic reviewing is a method that was developed in medicine and health to enable efficient access to sound research evidence and thereby improve health care decisions and outcomes. It is an important step in Evidence Based Practice.

A systematic review is an appraisal and synthesis of primary research papers using a rigorous and clearly documented methodology in both the search strategy and the selection of studies. This minimises bias in the results. The clear documentation of the process and the decisions made allow the review to be reproduced and updated.

Characteristics of a systematic review

A clearly stated set of objectives with pre-defined eligibility criteria for studies
An explicit, reproducible methodology
A systematic search that attempts to identify all studies that would meet the eligibility criteria
An assessment of the validity of the findings of the included studies, for example through the assessment of risk of bias
A systematic presentation, and synthesis, of the characteristics and findings of the included studies.

(Cochrane Handbook for Systematic Reviews of Interventions, 2022)

Team work

Systematic Reviews are usually a team effort. Important areas of expertise to cover are;

Content experts - It is important to have team members or an active consultant to provide expertise in the area covered by the review. Input is usually needed from practitioners and researchers representing a variety of perspectives.
Systematic Reviews methods experts - One or more persons with expertise in the methods of conducting Systematic Reviews is needed. This person may be responsible for developing the procedures and documentation standards for the review. A Systematic Review methods expert may also be a content expert, but more than one investigator-level reviewer is necessary, since some steps in the process require dual review or data checking that requires expertise in research and statistical methodology.
Statistician - If meta-analysis is to be considered, access to a statistician with experience in meta-analysis is needed.
Medical librarian - Database searching requires specialized knowledge that general research training does not provide. Preferably, the librarian searcher has experience with the extensive searching and documentation procedures that are a part of a systematic review.
Reference management - Someone must be responsible for maintaining the database of references. Most SRs involve thousands of abstracts, and the use of software to manage the references is necessary. This person must be able to track which abstracts have been reviewed and their disposition (e.g., included or excluded, reason for exclusion).

O'Connor, E., Whitlock, E., & Spring, B. (2007).

(Introduction to Systematic Reviews, EBBP)

What is the difference between a literature and a systematic review?

	Systematic Review	Literature Review
Question	Focused on a single question	Not necessarily focused on a single question, but may describe an overview
Protocol	A peer review protocol or plan is included	No protocol is included
Background	Both provide summaries of the available literature on a topic
Objectives	Clear objectives are identified	Objectives may or may not be identified
Inclusion and Exclusion Criteria	Criteria stated before the review is conducted	Criteria not specified
Search Strategy	Comprehensive search conducted in a systematic way	Strategy not explicitly stated
Process of Selecting Articles	Usually clear and explicit	Not described in a literature review
Process of Evaluating Articles	Comprehensive evaluation of study quality	Evaluation of study quality may or may not be included
Process of Extracting Relevant Information	Usually clear and specific	Not clear or explicit
Results and Data Synthesis	Clear summaries of studies based on high quality evidence	Summary based on studies where the quality of the articles may not be specified. May also be influenced by the reviewer's theories, needs and beliefs
Discussion	Written by an expert or group of experts with a detailed and well grounded knowledge of the issues

Reproduced from: Bettany-Saltikov, J. (2010). Learning how to undertake a systematic review: Part 1. Nursing Standard, 24(40): 47-55.

How are they used?

To help groups and individuals make decisions to improve people’s health. Examples include:

Recommendations and guidelines
[e.g., United States Preventive Services Task Force (USPSTF), National Institute for Health and Clinical Excellence (NICE).] Should smokers routinely be advised to use quit smoking medications? Should primary care providers routinely screen patients for depression? What should be the components of an intervention to help overweight children manage their weight?
Benefit design, coverage and policy decisions
[e.g., Centers for Medicare and Medicaid Services (CMS), Drug Effectiveness Review Project (DERP), UK National Health Service (NHS).] Should we cover the use of medication to quit smoking? Should we reimburse visits with breast feeding specialists in mothers with babies?
Public Policy
Would it improve the health of our community if we increase funding for mass transit and bike facilities?
Performance measures
[e.g., Assessing Care of Vulnerable Elderly (ACOVE).] If a patient receives a new prescription for an antidepressant, what frequency and duration of followup constitute good quality care?
Research agendas
[e.g., National Institutes for Health (NIH), Agency of Healthcare Research and Quality (AHRQ).] What are the gaps in the evidence related to treatment of anxiety in children?
Individual patient care
Should I advise this client to use behavioral treatment in addition to medication to help her quit smoking?
Patient decisions
Should I try hypnosis to help me get over my fear of flying?

Elizabeth, O. C., Whitlock, E., & Spring, B.

(Introduction to Systematic Reviews, EBBP).