Systematic reviews: finding and managing the evidence

What is a systematic review?

It’s widely acknowledged that health care decisions should be made on the basis of the best available evidence. However, with a large and growing body of research information out there of variable quality, it can be time-consuming and overwhelming for healthcare staff  and researchers to find that best available evidence. Systematic reviews help overcome this problem, and are important tools in providing evidence-based healthcare. 

Systematic reviews aim to  identify, evaluate and summarize the findings of individual studies, in a systematic and unbiased manner, thereby making reliable evidence more accessible to decision makers.

How do I go about  starting a systematic review project?

In order to create a true systematic review you need to first identify your research question and gather a team of people to fulfill the different roles.   Having a team of people helps with covering the different skills required for the different elements of the review and minimizes the risk of bias being introduced. Team members could optimally include:

• 2-3 Clinical subject experts who are work closely in the area of interest
• An information professional to support and advise the literature search process and document supply end
• A bio-statistician who can deal with the statistical side of a systematic review such as creation of meta-analyses
• An administrative officer who can look after any admin tasks related to the project, such as managing references and documenting the process
• If  you're not able to assemble as wide a team as suggested above, a true systematic review needs to be carried out by a minimum of two people.

What is a systematic review protocol?

All good systematic reviews will start with a protocol. A protocol  is a plan that sets out in advance the rationale for a review, its objectives and the methodology to be used with the aim of minimizing bias.  The Cochrane Collaboration define bias as 'a systematic error, a deviation from the truth, in results or inferences'. Creating a solid protocol  and adhering to it, can help minimize the risk of any bias being introduced into the systematic review process.

The protocol will outline the steps to be taken to locate, select and critically appraise studies and how study data will be collated  and analyzed and reported, making the review transparent and therefore reproducible by other researchers.

The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) Statement has been developed to make sure that all relevant methodological information is included in published reviews and, as a result, can also help guide reviewers’ understanding of the systematic review process and its main features. A by-product of this statement is the PRISMA-P checklist,  a useful guide to follow when writing a protocol. 

In 2021, PRISMA also published its guidance for literature search reporting.

More detailed information on systematic review methodologies can be found in the Cochrane Handbook for Systematic Reviews or the Campbell Collaboration's guidance.

Registering your review will hopefully avoid others carrying out similar reviews on the same topic, and likewise you can use publicly available review registers to check that you are not planning to  duplicate work already being carried out by other researchers.

The two best sources of registered reviews are:

1. PROSPERO: International Prospective Register of Systematic Reviews and

2. Joanna Briggs Institute - JBI 's Systematic Review Register 

What are the stages of a systematic review?

High quality systematic reviews are defined in advanced by a protocol (see above) that maps out how the reviewers will:

1. Identify all relevant published and unpublished evidence
2. Select studies or reports for inclusion
3. Assess the quality of each study or report
4. Synthesize the findings from individual studies or reports in an unbiased way
5. Interpret the findings and present a balanced and impartial summary of the findings with due consideration of any flaws in the evidence.

Hemingway, P. (2009) What is a systematic review?  http://bit.ly/2udFvYb

Framework for systematic reviews

Another useful  framework  is the  SALSA framework developed by Grant and Booth (2009). It gives an overview of the main components of the evidence synthesis process:

Search

Appraisal

Synthesis

Analysis

Grant, M.J. and Booth, A. (2009), A typology of reviews: an analysis of 14 review types and associated methodologies. Health Information & Libraries Journal, 26: 91-108. https://doi.org/10.1111/j.1471-1842.2009.00848.x

Image: http://guides.mclibrary.duke.edu/c.php?g=158201&p=1036021

What is evidence-based healthcare?

The most common definition of Evidence-Based Healthcare (EBH) is from Dr. David Sackett. EBH is “the conscientious, explicit and judicious use of current best evidence in making decisions about the care of the individual patient" ( BMJ 1996;312:71)

Why is it important?

Population-based outcome studies have found that therapies that are evidence-based have more positive effects on patient care than opinion-based healthcare. For example, heart attack survivors prescribed aspirin or beta-blockers have lower mortality rates than those who aren’t prescribed these drugs.

How do we go about it?

EBH comprises of 5 steps:

Step 1. A decision needs to be made arising from a patient’s care or service development.

Step 2. You formulate a focused question, accounting for your population group, problem, intervention and any comparisons or outcomes.

Step 3. You identify the appropriate resources to search for the best evidence — here’s where the library can help the most.

Step 4. Critically appraise the evidence- the library can help you here too!

Step 5. Implement in practice, if applicable.