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Comprehensive & Systematic Reviews

A guide to resources to help with conducting comprehensive reviews & services available from eTreadwell

What is a comprehensive review?

"Comprehensive reviews" is an umbrella term. It refers to any review where the literature search is exhaustive and documented in a detailed and thorough way in accordance with accepted standards to avoid outcome bias. Conversely, a non-comprehensive review (typically a narrative review) is not beholden to the same standards, rigor or time commitment. 

A systematic review is one type of comprehensive review. It is a review of a "clearly formulated question that uses systematic and explicit methods to identify, select, and critically appraise relevant research, and to collect and analyze data from the studies that are included in the review" (PRISMA Statement). Statistical techniques (meta-analysis) may optionally be used to analyze the results of included studies of a systematic review. For biostatistics consultations, contact the MGH Division of Clinical Research or the Harvard Catalyst Biostatistics Consultation Service. 

Comprehensive reviews are also protocol-driven. Similar to how one would not embark on primary research without a protocol, one should have a protocol in place before initiating a systematic review.

The table below breaks down which review types are considered comprehensive and which are not:

Comprehensive Reviews  Non Comprehensive Reviews
Systematic Reviews Narrative Reviews
Scoping Reviews Critical Reviews
Umbrella Reviews  
Integrative Reviews  
Rapid Reviews  

It's important to have a good understanding of whichever review type you would like to pursue. Below are articles that talk more in depth about the differences between reviews. You can also use the "Which Review Is Right For You?" tool to help guide you in choosing a methodology.

What comprehensive review services does Treadwell offer?

Treadwell offers two tiers of review service, adapted from Harvard's model:

Level I: Acknowledgement

Level II: Co-authorship

Initial consultation meeting

All level I services

Develop a Medline search strategy using controlled vocabulary and keywords

Offer advice on feasibility and construction of research question and methodology best practices

Identification and suggestion of other databases for extending search Edit sections of the protocol that document the search

Advice on citation and project management tools

Translate Medline search strategy into other databases using controlled vocabularies and keyword selections 


Create PRISMA-compliant search documentation
  Deliver citation results using a Covidence project after removing duplicates

Author literature search methodology for the final manuscript



Review manuscript before submission and draft responses to peer reviewers or editors if questions arise regarding the search


  • Due to the time-intensive nature of this work, a limited number of reviews can be worked on at a time so the service may not be available if maximum capacity has been reached.
  • As projects evolve, the librarian retains the right to change tiers to accurately reflect the nature of the work being conducted, as well as refuse co-authorship.
  • The lead investigator for the project must be an MGH employee.
  • If you request more than one project, they will be worked on sequentially not concurrently.
  • Project timelines may be extended if we do not receive timely responses from the team, if there are issues with the project and/or because of staff time off.

I'd like to work with a librarian on my comprehensive review. How do I get started?

NOTE: Due to overwhelming demand and not enough current staffing to handle it, we have been forced to temporarily suspend our comprehensive review service.

Unfortunately, our wait list has reached the point where we feel it's unrealistic to continue adding projects to the list. We suggest trying to leverage a librarian at a different institution if someone on your team has another affiliation, or hiring a contract librarian if you have the funds available. Additionally, below are some suggested resources outside of MGH that could help:

Tutorials and classes to learn how to perform the literature search:

Free instruction:

Fee-based instruction:

How to find a independent contract worker to perform the literature search:

Independent consultancies exist such as Systematic Review Consultants LTDEffective Evidence and others. You can also post a call for work to the following listervs: expert searching (requires Medical Library Association membership) or MEDLIB-L (no membership required).

We'll be working hard to have the ability to ramp back up our service in the meantime. If no other options are available to you, you can try us again in August to see where we stand with continuing the service at that time. If you have questions, please direct them to


Contact us if:

  • You would like to work with a librarian on a comprehensive review.
  • You are not sure if you require librarian assistance with a comprehensive review, but want to learn more. 

To begin the process, submit a request by filling out this intake form. Once your form has been reviewed, you'll receive an email arranging a time for a virtual consultation.

How do I conduct a comprehensive review?

Learn how to conduct systematic reviews in our Systematic Review Process and Systematic Review Standards pages.

Resources about other common comprehensive review methodologies are listed below. 

Scoping Reviews

Scoping reviews serve to synthesize evidence and assess the scope of literature on a topic. Among other objectives, scoping reviews help determine whether a systematic review of the literature is warranted.

Umbrella Reviews

Systematic reviews of systematic reviews

Rapid Reviews

Rapid reviews omit parts of the systematic review process to speed up the review process. 

Integrative Reviews

Integrative reviews are most often seen in the nursing discipline.

Living Systematic Reviews

Living systematic reviews are continually updated reviews that may be used to synthesize rapidly evolving areas of research. 

Covidence: Online Platform to Streamline Systematic Reviews

Treadwell provides access to Covidence, an online platform that aims to accelerate the systematic review process, at no cost to MGH employees. MGH employees can also invite individuals from outside of MGH to collaborate on systematic reviews at no cost. 

Covidence is accessible by computer or mobile device, and provides one convenient place to screen citations, assess risk of bias, and extract data. 

Access Covidence

To access Covidence, request an invitation here using your or e-mail address. Do not use your or address.

Have a MGH Covidence account already? Log in here.

Learn How to Get Started With Covidence

For videos and written instructions to help you get started with Covidence, see our support page in the Covidence Knowledge Base.