The number of different types of reviews is constantly growing. This guide looks at several of the most common types of reviews, but there are other kinds as well. If you are just starting out and trying to determine what type of review to do, Cornell University Library has created a handy chart for researchers.
Your friendly local health sciences librarian is here to help! Email me using the contact button in this research guide, or use the form below to request help with a scoping review.
A literature review (also known as a narrative review or narrative literature review) is a low-level review that provides a comprehensive summary of previous research on a topic. It can utilize and incorporate surveys, scholarly articles, books, and other sources relevant to a particular area of research. This type of review should summarize previous studies and clarify the previous research.
In writing the literature review, the purpose is to convey to the reader (or researcher) what general information there is on a topic, and what the strengths and weaknesses are with regard to that information.
There is no strict methodology for a literature review. The researcher can choose which databases or sources to use and how many. The researcher does not have to apply any strict inclusion/exclusion criteria on what to select and include. An exhaustive search to capture all relevant material on a given subject, adhering to a strict methodology, can be utilized but this is not typical.
Health Sciences Literature Review Made Easy by 
Literature Review and Synthesis: A Guide for Nurses and Other Healthcare Professionals by Provides an overview of all the available research evidence that is available on a topic. They often present findings in visual tables and graphs. One of the main uses of a scoping review is to identify any possible gaps in the current literature and justify either a full-fledged systematic review or primary study on a topic such as a randomized controlled trial.
The average timeframe of a scoping review can be anywhere between six months and eighteen months. Therefore, before you commit to a scoping review, the larger repositories such as PubMed, Joanna Briggs, and Cochrane, and PROSPERO should be looked at to see if there is already an existing scoping or systematic review on the subject. (Note: PROSPERO does not register scoping reviews at this time.)
To get the best answers, it is important to ask the best questions! Many reviews answer a question using PICO: Population, Intervention, Comparison, Outcome. Because scoping reviews are more broad than systematic reviews, their research questions may be formed using PCC rather than PICO.
Consult with your librarian to find usable keyword synonyms and relevant subject heading terms (keyword searches and subject heading searches produce different results). Isolating the perfect search synonyms lays the foundations for all the work to come -- invest time here! Link your terms together with Boolean operators to build your search string.
Determine which databases and other sources will be utilized. Librarians are considered experts in the field of research, so the mere act of consulting with your librarian will help the status and prestige of your review.
Once you have determined the final selection of keywords, run one last search across the big repositories: PubMed, Joanna Briggs, Cochrane, and PROSPERO should be looked at to see if there is already an existing scoping or scoping review on the subject.
In theory, registering your scoping review with a repository plants a flag in the topic that lets others know you are already researching it. You will have to write a 1-2 page protocol in order to register your review. There are multiple places to register your protocol.
Should you decide to register your review, per PRISMA protocols you will need at least one official search strategy from one database. Your librarian can help with this.
An exhaustive search of the literature should be undertaken and findings recorded on the recommended PRISMA diagram. Upload the results to a citation management system like RefWorks or systematic review software like Rayyan. Keep track of all of your decisions and steps; it will make writing the manuscript much easier as it may be six months to a year after you started the process.
How will you determine which articles should be excluded or included in your review? This should be done before you begin reviewing articles in order to avoid bias.
Once all the articles have been found and collated, a series of elimination rounds should take place per PRISMA protocols.
What you have left is commonly referred to as the "golden standard" -- those articles or book chapters that are a perfect fit for your review’s topic. Use these articles to find others that you may have missed during your search.
Once you have finished all of this, typically some time will have passed. It is highly recommended that one last search be conducted across the databases to pick up any new articles.
Have your librarian check the articles that have made it to your golden standard,' and subsequently, their citations, for any possible retractions.
At this point your librarian has helped you with everything within their scope and leaves the process.
Do a critical appraisal of your sources (optional).
Collate, chart, tabulate, and present your findings.
Systematic reviews are positioned towards the top of the evidence-based pyramid, with only meta-analysis and actual clinical guidelines coming above. Because of this, they are held in high regard and are the most sought after informational source for questions about health.
Their main objective is to evaluate and synthesize existing primary studies and/or other sources of information on a specific question into an equally specific answer and ensure the results of the review provide accurate evidence.
The average timeframe of a systematic review can be anywhere between twelve months and two years. Therefore, before you commit to spending all that time working, the larger repositories such as PubMed, Joanna Briggs, Cochrane, and PROSPERO should be looked at to see if there is already an existing systematic review on the subject.
To get the best answers, it is important to ask the best questions! For quantitative reviews, use PICO to form your research question:
Note: From a research perspective, including the outcome to your search string adds bias, so it should not be incorporated:
Consult with your librarian to find usable keyword synonyms and relevant subject heading terms (keyword searches and subject heading searches produce different results). Isolating the perfect search synonyms lays the foundations for all the work to come -- invest time here! Link your terms together with Boolean operators to build your search string.
Creating a protocol before diving into your systematic review allows the team to plan through the entire process before getting started, from searching and creating inclusion and exclusion criteria to creating a plan for extracting and synthesizing your data. Following the PRISMA guidelines would create a 1-2 page protocol that would help you plan out your review. A PRISMA protocol requires at least one official search strategy from one database for a systematic review, as well as an official search strategy for all databases utilized in the case of a systematic review. Your librarian can help with this.
In theory, registering your systematic review protocol with a repository plants a flag in the topic that lets others know you are already researching it. There are multiple places to register your protocol; we recommend PROSPERO for systematic reviews.
Determine which databases and other sources will be utilized. Librarians are considered experts in the field of research, so the mere act of consulting with your librarian will help the status and prestige of your review.
Once you have determined the final selection of keywords, run one last search across the big repositories: PubMed, Joanna Briggs, Cochrane, and PROSPERO should be looked at to see if there is already an existing systematic review on the subject.
An exhaustive search of the literature should be undertaken and findings recorded on the recommended PRISMA diagram. Upload the results to a citation management system like RefWorks or systematic review software like Rayyan. Keep track of all of your decisions and steps; it will make writing the manuscript much easier as it may be six months to a year after you started the process.
How will you determine which articles should be excluded or included in your review? This should be done before you begin reviewing articles in order to avoid bias.
Once all the articles have been found and collated, a series of elimination rounds should take place per PRISMA protocols.
What you have left is commonly referred to as the "golden standard" -- those articles or book chapters that are a perfect fit for your review’s topic. Use these articles to find others that you may have missed during your search.
Once you have finished all of this, typically some time will have passed. It is highly recommended that one last search be conducted across the databases to pick up any new articles.
Have your librarian check the articles that have made it to your golden standard,' and subsequently, their citations, for any possible retractions.
At this point your librarian has helped you with everything within their scope and leaves the process.
When you arrive at your final selection of articles, it is time to evaluate them. There are a variety of critical appraisal tools out there; find one that is appropriate for your particular type of study.
Synthesize the evidence and draw your conclusions, then present your findings.
Systematic Reviews in Educational Research by 
Assembling the pieces of a systematic review : guide for librarians by Mixed method isn't so much a type of review in and of itself; rather, it is an approach that can be taken with existing review types, e.g., a mixed methods literature review, a mixed methods systematic review, etc..
Mixed-method reviews include elements of both quantitative and qualitative research that are merged together. Combining objective numerical data sets with subjective observational data is a difficult task that has the potential to either produce a holistically greater whole or go asunder badly.
Depending on what level of review you are applying the Mixed Methods approach to will determine the need to conduct an exhaustive search or not. For example, a mixed-methods systematic review would require an exhaustive search while a mixed-methods literature review would not. (See more on our search strategy page.)
The best way to integrate the two datasets is ask yourself what question it is you are trying to answer, and what element(s) from each technique would serve to enhance that answer. This is why you need to fully understand the strengths and weaknesses of each.
Mixed Methods Research by Meta-analysis is the statistical procedure for combining data from multiple studies.
In order to conduct a meta-analysis you must first have completed a systematic review. It is highly suggested if you plan to conduct a meta-analysis that your systematic review be limited to those studies that produce quantifiable, numerical data sets, e.g., randomized controlled trials.
As different studies will have different variables, such as participant numbers, different standards of quality control, et cetera, so too will they show differing results. The results of one randomized controlled trial do not provide definitive proof of an interventions success on a particular health condition.
However, if several randomized controlled trials can be found on the same subject and are similar enough that they can be equated, then they can be put through standardized statistical procedures. Their results can be subsequently combined via such instruments as a forest plot graph. It becomes possible to observe whether or not there is a a statistically significant degree of success for whatever intervention is being looked at on the condition being studied.
While certain reviews such as a narrative review or a systematic review can be used for the purpose of synthesizing the results of multiple studies, these reviews can be subjective (different experts can come to different conclusions). Meta-analysis, by contrast, applies objective statistical formulas to the data collected.
Meta-Analysis by