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Systematic Reviews and Meta-Analyses: Exploratory Search

This guide is designed to help novice and experienced review teams navigate the systematic review and/or meta-analysis process

Illustrates the exploratory searching phase. Begin with an initial research question; run initial searches in a few databases and web browsers; locate existing and/or in-progress reviews as well as seminal articles; refine the research question and eligibility criteria; rerun initial searches and continue refining scope until you have a usable scope.

Exploratory Search

Once you have an initial research question, you can develop and refine your research question and eligibility criteria through exploratory searching. Exploratory searching is also called preliminary, initial, and naive or novice searching. Regardless of what you call it, it is simply a series of searches conducted prior to starting the review with the goal of producing a well-defined scope with clear demonstration of contribution to the field. This is an iterative process as illustrated in the image to the right. 

Throughout the exploratory search you should collect A. existing and in-progress reviews and B. seminal articles related to your scope. Ultimately, this phase should help your team produce

  • A clear, well-defined scope 
  • 2-5 Seminal articles to validate your search later on 
  • Context of what has been done to address this question, illustrating that this review does not duplicate existing or in-progress publications

At the bottom of this page, we also suggest C. where to start exploratory searching.

A. Existing & in-progress reviews

Does your review already exist?

Before starting, make sure a systematic review hasn't already addressed, or is in the process of addressing your research question(s). 

You should look for published systematic reviews, but also check out review registries and general purpose repositories (e.g., Open Science Framework) where you're more likely to find unpublished or in-progress reviews and/or review protocols. Searching registries will give you a glimpse into the work that is being done currently, but isn't yet complete. Remember, this kind of review is a serious time-commitment, and you don't want to unknowingly duplicate efforts.


Existing and in-progress reviews on similar, non-identical topics can be helpful when identifying where to search and developing the search strategy and data extraction forms!

Searching tips

In academic journal databases, you can sometimes find a filter for Systematic Reviews, Meta-Analyses, and/or simply Reviews. If a built-in filter doesn't exist, you can add the term "review" to your search.

Initial Research Question: Does drinking coffee reduce the likelihood of falling asleep while driving?

(coffee) AND (sleep) AND (driving) AND (review)

 

If you get too many results, you can specify the kind of review:

(coffee) AND (sleep) AND (driving) AND ("systematic review" OR "meta analysis")

 

What if my review already exists?

We pursue systematic reviews and/or meta-analyses to answer a research question. If a review already answers your question, this existing review can be the foundation of your next research project!


Pursuing a different review

Sometimes it is still important to pursue a review, even if your original research question(s) have been answered. What is considered "the same" review is not always clear. Generally speaking, you need to justify that and illustrate how your new review contributes something unique to the field. 

If a review already answers your question, and your team would still like to pursue a review, your team can:

  • Update reviews that are out of date
  • Enhance reviews with significant limitations / quality concerns
  • Attempt to replicate the review 
  • Revise your original question 

Updating a Review

According to Garner, et al., (2016), "The decision [of whether or not to update] needs to take into account whether the review addresses a current question, uses valid methods, and is well conducted; and whether there are new relevant methods, new studies, or new information on existing included studies. Given this information, the agency, editors, or authors need to judge whether the update will influence the review findings or credibility sufficiently to justify the effort in updating it."


Additional Guidance

Bashir, R., et al. Time-to-update of systematic reviews relative to the availability of new evidence. Syst Rev 7, 195 (2018). https://doi.org/10.1186/s13643-018-0856-9

Garner, P., et al. Panel for updating guidance for systematic reviews (PUGs). (2016). When and how to update systematic reviews: Consensus and checklist. BMJ, i3507. https://doi.org/10.1136/bmj.i3507


Replicating a Review

Review replication is not often pursued due to the amount of time and labor required. However, Pieper, Heß, & Faggion (2021) have developed a framework for replicating, and the replication process is a great learning tool.


What if a restricted / rapid review, or a scoping review exists, but not a systematic review?

You may find other reviews (e.g., scoping review, restricted (or rapid) review) on your topic exist - that's great, as these might provide further insight to the appropriateness of the systematic review method for your research question(s) and how to frame your own review approach.

B. Seminal Articles

DecorativeWhat is 'Seminal Work'?

In general, seminal work also called pivotal, landmark, or seed studies, are articles that are central to the research topic and have great importance and influence within the discipline. Seminal articles are likely to be cited frequently in different journal articles, books, dissertations etc. 


Seminal Articles in Systematic Reviews

In systematic reviews and/or meta-analyses, seminal work are the "seed articles" for your specific review - the articles (or other material) you know need to be included in your final synthesis. These articles may have sparked the teams interest in pursuing a review or may be identified through the exploratory search.

 


Seminal articles can be helpful when identifying where to search and developing the search strategy!

C. Where to "Exploratory Search"?

Where to Exploratory Search?

In short, where you exploratory search will depend on your research question. In other words, you should consider searching wherever you are likely to find material that answers your research question.


Databases

In addition to repositories, you'll want to search academic journal databases that may be relevant to your topic. Consider your topic from perspectives other than your own discipline - it's likely your topic overlaps with several disciplines. For example, if you are examining a public health topic, it may be useful to search databases related to health / medicine and social sciences.

You can also use this exploratory phase to determine whether a database is relevant and should be searched as part of your final comprehensive systematic review search strategy, or not.

Check out the VT libraries "A-Z Database List", or Librarian curated Library Guides related to your discipline!

Hint: Sort "By Subject" to find relevant guides


Web Browsing

Web browsing in Google or Google Scholar is a great place to start finding seminal works and existing reviews, as well as journals and databases in which you should conduct more robust exploratory searches.

Never rely only on web browsing. While Google Scholar (and Google) are great places to start searching, results are tailored to individual users, are not replicable, and algorithms are not transparent. More guidance for web browsing is located in the "Where to Search" sub-tab of the "Comprehensive Search" section of this guide.


More places to search...

The possibilities of where to exploratory search are endless! Consider searching anywhere that seminal articles or existing/in-progress reviews relevant to your scope may exist. Here are a few more places to get you started.


General Purpose Repositories

Researchers use these sites to share unpublished or in-progress research and reviews, procedural documentation, and other grey literature. For example:


Repositories that contain Preprints

Researchers uses these sites to openly share research, some of which is not yet published (or peer-reviewed), also called 'preprints'. For example: 

Systematic Review Repositories

There are several systematic review repositories that exist - some contain only published reviews, while others include review registrations and protocols. In the following table, we present and link out to some repositories that specifically house systematic reviews and similar evidence synthesis publications.


Campbell Collaboration Registry

"...all registered titles for systematic reviews or evidence and gap maps that have been accepted by the Editor of a Campbell Coordinating Group. When titles progress to protocol stage, the protocol is published in the Campbell Systematic Reviews journal."

Campbell Systematic Review Journal

Both registry and journal include topics related to Business and Management, Climate Solutions, Crime and Justice, Disability, Education, International Development, Knowledge Translation and Implementation, and Social Welfare

Cochrane Database of Systematic Reviews (CDSR)

"...the leading journal and database for systematic reviews in health care. CDSR includes Cochrane Reviews (systematic reviews) and protocols for Cochrane Reviews as well as editorials and supplements."

Cochrane Library

"Cochrane Collaboration produces high-quality systematic reviews in health disciplines. For more detail and specific fields of research, check out the Cochrane Review Groups and Networks."

Database of promoting health effectiveness reviews (DoPHER)

"...focussed coverage of systematic and non-systematic reviews of effectiveness in health promotion and public health worldwide. This register currently contains details of over 6,000 reviews of health promotion and public health effectiveness."

Epistemonkios 

"...a collaborative, multilingual database of health evidence. It is the largest source of systematic reviews relevant for health-decision making, and a large source of other types of scientific evidence."

Health Evidence

"...quality-rated systematic reviews evaluating the effectiveness and cost-effectiveness of public health interventions, including cost data."

Joanna Briggs Systematic Review

"...a collection of world-class resources driven by the needs of health professionals and consumers worldwide"

Prospero

"International database of prospectively registered systematic reviews in health and social care, welfare, public health, education, crime, justice, and international development, where there is a health related outcome."