Systematic review guide

There are many different types of reviews of literature, suiting different types of evidence and serving different purposes. This 2019 article "Meeting the review family: exploring review types and associated information retrieval requirements" by Sutton, Clowes, Preston and Booth found 48 types that they then categorised into 7 "review families".

This guide by University of Melbourne provides a clear descriptions and information about different review types. 

The main types of review at Imperial College London

• Literature reviews/ Narrative reviews: this traditional type of review describes the amount and nature of evidence on a topic, but without formal appraisal or synthesis. Accuracy and replicability are not the focus of literature reviews and as such, the author has more leeway to introduce their own understanding and so the conclusions can be biased. The synthesis and summary is is often in words (narrative) rather than employing statistical methods. While it is helpful to still search systematically for efficiency, the strategy does not have to aim for comprehensiveness.
  In the article "Time to challenge the spurious hierachy of systematic over narrative reviews?" (linked below) Greenhalgh, Thorne and Malterud argue that while narrative reviews are generally assumed to be a weaker class of evidence than systematic ones, both serve different purposes and should be viewed as complementary. They see the key contribution of a narrative review as providing interpretation and critque.
  More information about doing one of these reviews can be found in our Literature Search Tutorial.  

• Scoping reviews: while a systematic review such as an effectiveness or interventional review looks for a specific answer in a narrow topic e.g. "is this treatment more effective than that treatment on a this population with this disease?" a scoping review looks at multiple answers or a wider viewpoint e.g. "what are the barriers and facilitators for these people doing this activity in this setting?" This review type won’t affect your information searching too much as you will still be aiming to have a fully comprehensive search strategy but may affect how you analyse or describe the results. These reviews can be confused with mapping reviews and evidence and gap maps. This graphic from JBI shows the differences between them. Like a systematic review, scopings reviews should be conducted systematically and transparently.

• Umbrella Reviews: a systematic review of reviews. If a number of similar scoping or systematic reviews have been done on a topic it can be useful to do an umbrella review to assess all the higher levels of evidence on a broad but well defined research topic. 

• Rapid Reviews: due to time constraints, most of the reviews conducted at Imperial are actually rapid reviews. You should still be aiming to have a comprehensive and reproducible search strategy that follows the process of doing a systematic review. But you can do it in less time by narrowing the scope of the question, limiting the search e.g. by study design or year, only using single researchers at certain stages of the screening, data extraction and risk of bias assessment (with the second reviewer just checking a certain percentage) and writing up a descriptive or narrative summary rather than doing a meta-analysis.