Systematic review guide

According to the PRISMA 2020 statement (pdf), systematic reviews "can provide syntheses of the state of knowledge in a field, from which future research priorities can be identified; they can address questions that otherwise could not be answered by individual studies; they can identify problems in primary research that should be rectified in future studies; and they can generate or evaluate theories about how or why phenomena occur".

A systematic review must:   

• aim to discover, and be inclusive of, all revelant studies to find all the data available to answer the focused research question
• minimise bias using explicit, systematic methods that are planned and documented in advance with a protocol
• be transparently reported, including publishing search strategies, so that the results can be verified or reproduced, using a suitable reporting guideline (such as PRISMA 2020)

Systematic reviews are time and resource intensive

Systematic reviews are a valuable resource but doing one is often much more work than researchers anticipate and not as some people believe,  a quicker or easier option than other reseach methologies. For example, an average Collaboration for Environmental Evidence review was found to take 164 days. The Cochrane Handbook used to say that a review would take a professional review team 12 months to complete a review (with 1/3 of that time spent on developing the search strategy). Even with a growing number of tools that help to manage (and sometimes partially automate some review steps) the process of preparing for the review and then discovering, analysing and synthesising all the data remains very time consuming.

The PredicTER will help you predict the time needed for your review. It was designed to help with grant applications but can also be used to understand how much work your review will entail.

When is systematic review not a systematic review?

Often when people say they have completed a systematic review they just mean that they have searched more than one database systematically. It means that they have made (and hopefully reported) a thorough search strategy, which can be reproduced by other researchers, and used this in several databases to find many resources that provide the evidence to support their argument. However, without a systematic appraisal and synthesis of the literature it remains a literature review, not a systematic review. There is still academic and clincial value in doing this, but it should not be published claiming to be what it is not. To be a systematic review all methodological guidelines should be followed, otherwise it is as incorrect and misleading as labelling your study as a Randomized Controlled Trial when it fact it was a pilot or feasability study. Equally, a review where only one database has been searched can also not claim to be a systematic review, or if it does, it is a very poor quality one!

Calling a literature review where you have employed some of the techniques and methods of a systematic review a "systematic review" may be appropriate in some circumstances such as for assessed coursework but if you are unsure please ask your course or a librarian for more advice.