When I first started in medical communications, narrative review articles were much more commonplace within a publication plan. In recent years, my experience is that non-commissioned, non-systematic review articles can often take a long time to develop, and deliver little value to the medical community. So how can we ensure those few review articles within publication plans are valuable additions?
The first question to ask is whether the review article is going to add anything new to the medical literature. A simple PubMed search will show if there is anything recent on the topic. If not, perhaps there is a legitimate gap and the project worthwhile considering further. The next critical step should be to identify the appropriate target journal. Once identified, a presubmission enquiry to the journal editor is sensible, and a thorough understanding of the journal requirements for review articles is essential. Many of the higher impact factor journals and society journals only take commissioned articles and others do not permit industry involvement/funding. Also, I have seen more and more journals requiring or recommending that review articles pre-register their protocols on PROSPERO.
PROSPERO is an international database of prospectively registered systematic reviews and is funded by the United Kingdom's National Institute for Health Research (NIHR). PROSPERO requires a protocol to be submitted before data extraction has occurred and protocols are published on an open-access searchable database. The database is also worthwhile searching before planning a new review to ensure a similar review isn't already in planning/development.
The main disadvantage of PROSPERO is that it relies on the integrity of researchers for the accuracy of the data supplied and my sense is that a lot of the records are not up-to-date. By the end of this year, >100,000 systematic reviews are likely to be registered (see below), but <10% are categorised as published. Over 80% of the review protocols are catgorised as "ongoing", which is understandable for reviews registered this year and last, but unlikely for those registered more than two or three years ago.
Systematic review protocols on PROSPERO:
A deeper dive into the PROPERO database actually shows approximately 40% of reviews initially registered in 2011 (n=284) are categorised as ongoing. A further delve supports the notion that some of the database information is outdated. For example, I am pretty certain this 'ongoing' review here has now been published here. Fortunately, the database provides enough information (anticipated completion date; contact details for further information) to allow follow-up on any relevant records that are suspected to be out-of-date.
Even when a review article is not envisaged to be rigorously systematic, and therefore cannot be registered on PROPSERO, a formal search strategy that can be reported in the manuscript, is valuable. Certainly, nwith systematic reviews, the most important key step is to understand the reporting guidelines. PRISMA is an "evidence-based minimum set of items for reporting in systematic reviews and meta-analyses" first published in 2009, with an update expected in 2020. Matthew Page of Monash University provides a nice summary of what's expected in that update in the video below.
PRISMA 2020 update:
The other useful guidelines are the recently reported SWiM guidelines for "Synthesis without meta-analysis" in systematic reviews. For enhanced understanding of systematic review development, the Cochrane Training website is another invaluable resource.
Certainly, development of a systematic review is more rigorous, and therefore more time-intensive than a narrative review, but the lack of rigour of a narrative review article often increases the likelihood of journal rejection unless the article is solicited or the topic pre-agreed with the journal. The advantage of a narrative review is that the authors have greater flexibility, such as bring able to approach different aspects of a particular theme to differing degrees, or to cover several related topics/questions in a single article. As with any project, (1) asking the right questions about the purpose of the project and its ultimate goal (before it is started!) and (2) understanding the pros and cons associated with each approach will guide whether a systematic or narrative review is better in any particular case.