Systematic Reviews - a quick guide: Stages of a Review

There are a number of stages to a systematic review. These are:

• Identify a research question - Developing a clear and answerable question is the first step to carrying out a systematic review. Many questions in the health arena are guided by a tool called PICO. This mneumonic stands for

Problem/Population

Intervention

Comparison

Outcome

Such questions tend to be be looking for quantitative research, often only randomised controlled trials. An example of a typical PICO type question would be

How does the use of exercise compare with the use of pain medication in treating postoperative pain following hip surgery?

However, there are other types of health related research questions which do not naturally fit with PICO and a number of other tools have been developed to help with question formulation and search strategy. These include SPICE and SPIDER. These tools are often more suited to questions which are qualitative in nature. See below for what these mneumonics stand for

• Inclusion and exclusion criteria defined

Before starting the search for relevant studies you need to decide on your inclusion and exclusion criteria. These should be outlined in your systematic review protocol.

The inclusion criteria is everything a study should have for it to be included in your review.

Exclusion criteria are the factors that would make a study ineligible for inclusion in your review.

Such criteria could include age of study, population, outcomes, type of methodology.

• Search for studies

Carry out thorough searches on the databases you have identified. To help to ensure your search strategies are comprehensive work or consult with a librarian. In addition to your database searching search elsewhere including sources to locate gray literature and trials registers if appropriate. 

Use reference management software such as Legacy RefWorks or EndNote to store all your references in one place. This software will also enable you to deduplicate before carrying out the screening stage.

• Study selection based on predefined criteria

Screen the titles and abstracts of retrieved studies to remove ones which are clearly not related to your topic. Then use your inclusion/exclusion criteria with the full-text of the remaining studies to identify ones which should not be included. Two independent reviewers should be involved in the study selection stage. Where there is disagreement between reviewers about individual studies a consensus should tried to be reached. If this is not possible a third party should be consulted. 

• Data extraction from included studies

A data extraction tool or systematic review software should be used to extract all the relevant data from individual studies. It is highly recommended that the tool is piloted to assess its' suitability.

• Conduct risk of bias of included studies

A risk of bias tool such as Cochrane's such as ROB 2 should be used to assess for different kinds of bias.

• Presentation of results and assessment of the quality of evidence

Your findings should be presented in a very clear way and include information such as your search strategy. This will make any future updates easier. If appropriate perform a meta-analysis. If there is sufficient high quality evidence make recommendations for practice and policy making. If there is insufficient quality evidence make suggestions for future research which would help to fill the knowledge gap and strengthen the body of evidence.