I`m trying to publish a systematic review and in the flow diagram the final number of papers is 13. One of the reviewers claims that 13 is not an adequate number for a systematic review. However, I can't find information about the minimum number of papers to analyse. How can I answer this point by quoting some paper or manual?
If these 13 articles were retrieved after search and duplicate removal, it is inadequate, indicating a wrong search strategy. But if it is the number of included studies after the full-text screening, it is quite enough. In that case, I don't think that reviewer's comment is evidence-based. Even some of Cochrane's reviews reach 1 or 2 final included articles at the final stage. If the process is right, there is no limitations for the results.
To emphasise Mohammad Hosein Amirzade-Iranaq 's point - this is a very strange point for the reviewer to raise if the number of included articles is indeed 13. If the case is as simple as it appears my suggestion would be to enquire of the journal editor how they suggest you respond - I assume that you are being invited to revise? You can't magically make additional studies appear. However, I do find how you phrased this odd: "in the flow diagram the final number of papers is 13". If the final number of papers that you have included (which meet your criteria) is 13 - I am unsure what the flow diagram has to do with it - that's just a standard way of reporting it in a paper.
I suggest that you consider the following:
i) As Mohammad Hosein Amirzade-Iranaq suggests- are you the reviewer talking results of your searches (hits) as opposed to included papers? A low number of hits is likely to result from a very limited/ineffective search strategy.
ii) Is it possible that the reviewer is saying that 13 studies is low because they know or suspect that there should be more? If so consider whether or not your searches should be amended to check whether you do in fact have all relevant studies.
Occasionally reviewers do just say things that are wrong...
Peter
I agree with both previous comments. If your systematic review retains only 13 it means that there are only 13 studies to answer to your question (which per se is an important information to report to your research area). The number of 13 is quite high in various fields of research. In my area (veterinary science) having 13 studies is very high number (sometime we hardly finish with-3-7 studies...). Sometimes reviewers throw comments just because of a "guts feeling" but without any science beyond this.
In case it may helps you can see this following peer reviewed references addressing specific issues on very small samples (
- Badges
- Science topic
- Similar topics
- Social Psychology
- Attitude