The number of published systematic reviews continues to grow and so the challenge of ensuring that they are current and fit for purpose becomes even more important. A study published in 2010 estimated that there were approximately 75 new trials, and 11 new systematic reviews of trials published per day – this figure is now likely to be even higher.
It’s widely accepted that systematic reviews have the potential to ensure best practice and improve healthcare by enabling users to make decisions based on the totality of the available evidence.
However, if we fail to keep systematic reviews up-to-date this could lead to healthcare decisions being made on out-of-date or potentially misleading evidence, which can have a detrimental impact on patient care.
This in itself is a balancing act; updating too soon may introduce bias, as trials with significant results are more likely to be completed sooner and published quicker. Updating also requires substantial investment in time and resources and so “ad-hoc” and untimely updating may be an inefficient use of limited resources available to prepare and maintain systematic reviews.
… if we fail to keep systematic reviews up-to-date this could lead to healthcare decisions being made on out-of-date or potentially misleading evidence…
Why should I update a systematic review?
The decision to update a systematic review needs to be made carefully. It’s important to consider whether the topic under review is still relevant to decision-making and thus worthy of updating.
For example, if a treatment is no longer used for a particular condition or if more effective interventions have been developed, it would be an inefficient use of resources to update that review – recognizing that sometimes these decisions are geographically based. Alternatively, if the efficacy of a given treatment has been well established, the addition of new studies is less likely to change the overall results and would again result in an inefficient use of resources.
If it is decided that the topic is still current and worthy of updating, the most common reason to update a systematic review is the addition of new research studies. However, other factors should also be considered, including the addition of new treatment regimes, population subgroups, new outcome measures, new study designs or data from ongoing studies.
Changes to the cost associated with the intervention under review and its importance to funders and decision-makers are also important factors to consider.
As the science of systematic reviews develops, so do their methods. As new methods of analyzing and synthesizing data become available, the methods of a systematic review also need to be assessed to ensure that they are still appropriate and up-to-date.
When should I update a systematic review?
Currently, there are no guidelines on the optimal time point at which to update a systematic review. The two-year rule, which until recently was the policy for updating Cochrane reviews, was based more on the wish for findings to appear current and up-to-date by the end user than evidence that this is an appropriate time interval.
In practice, reviews in rapidly moving fields may need to be updated more often than every two years, and other reviews, where the evidence is relatively stable, might require updating less often.
Where should I publish a systematic review update?
The journal Systematic Reviews recognizes the importance of publishing updated systematic reviews and have introduced the article type “systematic review update” which you can select when submitting your article.
The journal’s guiding principle for an update is that it is an event that is discrete and distinct from the conduct and reporting of the original systematic review (or previously updated review). This means that at a minimum the search for studies will have been brought up to date and that any changes to the results and conclusions of the original review (or a previously updated review) are described. The journal encourages authors to be innovative in how they report and present systematic review updates and welcomes your submissions!