I got asked to review a systematic review in a peer-reviewed Pubmed-indexed journal. However, based on the author’s inclusion/exclusion criteria, they only review one article.
Isn't that peculiar? As a reviewer, how should I respond to this? Is this acceptable, only one article...?
If it’s a systematic review, it is weird that there is only one article to include. However I think it could happen. After having applied inclusion criteria to all articles first retrieved, only one was left. I also think there’s a lesson out of this issue that the authors of the review should address.
Is it peculiar? Yes. How should you respond? Ask yourself if the "review" of only one paper adds anything meaningful to the literature on the subject. Perhaps the answer is 'yes' -- e.g. if the authors make a strong case that the subject is very under-explored, such that only one paper on it exists though many important questions exist to be answered. Or perhaps the answer is 'no.'
If there are a considerable amount of other works which were excluded using the criteria, resulting in one included work, then I would expect a justification for the exclusion criteria (perhaps it was too extreme?).
If there are not a lot of other works in this field, I would expect a justification of why the authors conducted a systematic review in this particular field (as hinted by @Raghu Parthasarathy).
In any case, I would expect the author to clearly acknowledge and explain this odd situation somewhere in the paper.
I think it depends very much on the exclusion criteria, and what the authors make of the single paper. For example, if it's just a review of that paper...it might not be particularly useful. However, many systematic reviews discuss the literature in the context of the field as a whole - is it surprising that this field only has one paper when a given exclusion criteria is applied? Is it possible the field is accidentally ignoring something because it's similar to something else?
