Wednesday, June 10, 2020

It’s Alive! Pt. I: An Introduction to Living Systematic Reviews

As research output continues to rise, the systematic reviews charged with comprehensively identifying and synthesizing the evidence within them are becoming more quickly out-of-date. In addition, the formation of a systematic review team can be a lengthy process, and institutional memory of the project is lost when teams are disbanded after publication.

One solution to this problem is the concept of a living systematic review, or LSR. In the first installment of a 2017 series in the Journal of Clinical Epidemiology, Elliott and colleagues introduce the concept of an LSR and provide general guidance on their format and production.

What is a Living Systematic Review (LSR)?
An LSR has a few key components:
  • Based on a regularly updated search run with an explicit and pre-established frequency (at least once every six months) to identify any potentially relevant recent publications. 
  • Utilize standard systematic review methodology (different from a rapid review)
  • Most useful for specific topics:
    • that are of high importance to decision-making,
    • for which the certainty of evidence is low or very low (meaning our certainty of the effect may likely change with the incorporation of new evidence), and
    • for which new evidence is being generated often.

A figure from Elliott et al. (2017) provides an overview of the LSR development process, from protocol to regular searching and screening and incorporation and publication of new evidence.

LSRs from End to End
An LSR can either be started from scratch with the intention of regular screening and updating of evidence – in which case the protocol should specify these planned methods – or based upon an existing up-to-date systematic review, in which case the protocol should be amended to reflect these changes.

Due to their nature, the publication of LSRs requires the use of an online platform with linking mechanisms (such as CrossRef) or with explicit versions (such as the Cochrane database) that can be updated as soon as new evidence is incorporated.

When the certainty of evidence reaches a higher level, or if the generation of new evidence substantially slows, an LSR may be discontinued in favor of traditional approaches to updating.

Additional Resources
Further information and support for the development of LSRs, including updated official guidance, is provided on the Cochrane website.

Elliott, J.H., Synnot, A., Turner, T., Simmonds, M., Akl, E.A., McDonald, S... & Thomas, J. Living systematic review: 1. Introduction - the why, what, when, and how. J Clin Epidemiol, 2017; 91:23-30.

Manuscript available from the publisher's website here.