The review question and inclusion criteria were clear. The search covered three relevant sources, although there was no specific attempt to locate unpublished studies. Only one author was credited, which suggested that review processes were not carried out in duplicate, so the risk of errors or bias in the review process should be taken into account in interpreting the review.
Trial quality was assessed using standard criteria, although only summary scores were presented. Other limitations of included trials were discussed in the text. A narrative synthesis was appropriate in view of the differences between the included trials. The synthesis presented was limited and mainly devoted to highlighting the limited evidence base.
The review had some methodological and reporting weaknesses but the author's conclusions reflect the limitations of the evidence and are likely to be reliable. The conclusions were also supported by another systematic review with different inclusion criteria (see linked record).