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Summaries of Cochrane Systematic Reviews: making high-quality evidence accessible

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The first paper in this edition of Spinal Cord pulls together what we know from different systematic reviews about the effectiveness of various treatment options for the management of pressure ulcers with a particular emphasis on Cochrane Systematic Reviews [1]. The review includes studies conducted on people with all types of conditions, not just spinal cord injuries (SCI). The strength of such a broad review is that it increases the accessibility of some important Cochrane Systematic Reviews. It also encourages us to look at evidence from populations without SCI while reflecting on the implications for people with SCI. But of course, it also highlights just how few clinical trials involving people with SCI and pressure ulcers have been conducted.

It is useful to summarise Cochrane Systematic Reviews because Cochrane Systematic Reviews can be technical, lengthy and difficult to read—some are over 100 pages long. In addition, evidence of the effects of the treatment options for a problem such as pressure ulcers are dispersed across many different reviews. For these reasons, summaries of related Cochrane Systematic Reviews are becoming increasingly popular. The Cochrane Handbook contains a chapter devoted to this topic titled—“Overviews of Reviews” [2]. These types of summaries of systematic reviews are also called “Umbrella Reviews” [3].

Cochrane Systematic Reviews are generally considered reliable summaries of the evidence. They have earnt this badge of honour because The Cochrane Collaboration has developed stringent methodologies to reduce bias and ensure trustworthy interpretation of the evidence. The level of evidence for a treatment is rated using the GRADE methodology which takes into account more than merely whether the evidence comes from a clinical trial which reports a few significant p values [4]. A typical Cochrane Systematic Review is preceded by a detailed protocol. Both the protocol and the review undergo meticulous scrutiny by methodological experts. In addition, authors of Cochrane Systematic Reviews are provided with training and support.

Often Cochrane Systematic Reviews span several conditions—they do not solely focus on one pathology. For example the Cochrane Systematic Reviews on management of pressure ulcers include treatment options for people who are elderly, in a coma, as well as people with SCI. There are advantages and disadvantages to including people with different pathologies in one review. The obvious advantage is the increase in the pool and quality of available data. The disadvantage is that treatments that are applicable and effective for one group of patients may not be so for another group of patients. However, a lot of what clinicians do and have accepted as normal practice in SCI is based on what we know about the response of people without SCI to various interventions and care.

Despite the obvious need to look further afield there is still a tendency to ignore what is known from studies conducted on people who do not have SCI, and rely solely on the results of studies involving people with SCI. This may be a mistake, particularly for those interventions that have only been tested on people with SCI in studies that are highly vulnerable to bias. In some situations, we may do better to look at higher quality evidence involving non-SCI populations. The limitations of relying on non-SCI-specific evidence can be captured in the Cochrane GRADE system for evaluating evidence by downgrading evidence for “indirectness” [5].

With this vision for the future, I welcome the current paper which summarises Cochrane Systematic Reviews and other types of reviews which deal with pressure ulcer management. It draws our attention to what is known about pressure ulcer management from patients with a range of pathologies and emphasises the need for more SCI-specific research on this important topic.

References

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    Atkinson RA, Cullum NA. Interventions for pressure ulcers: a summary of evidence for prevention and treatment. Spinal Cord. 2018;56:186–98.

  2. 2.

    Higgins J, Green S, editors. Cochrane handbook for systematic reviews of interventions version 5.1.0 (updated March 2011). The Cochrane Collaboration. 2011. http://handbook-5-1.cochrane.org/

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    Aromataris E, Fernandez R, Godfrey C, Holly C, Khalil H, Tungpunkom P. Methodology for JBI umbrella reviews. Joanna Briggs Institute Reviewers’ manual. North Adelaide, Australia: The Joanna Briggs Institute; 2014. pp. 1–34.

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    Guyatt G, Oxman AD, Akl EA, Kunz R, Vist G, Brozek J, et al. GRADE guidelines: 1. Introduction—GRADE evidence profiles and summary of findings tables. J Clin Epidemiol. 2011;64:383–94.

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    Guyatt GH, Oxman AD, Kunz R, Woodcock J, Brozek J, Helfand M, et al. GRADE guidelines: 8. Rating the quality of evidence--indirectness. J Clin Epidemiol. 2011;64:1303–10.

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Correspondence to L. A. Harvey.

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