The review question was clearly stated. A number of relevant databases were searched, but the apparent restriction to English publications may have introduced language bias. There was no apparent search for unpublished papers, so some potentially relevant papers may have been missed. Publication bias was reported to have been assessed, but the results were not reported. Review processes were not reported, so reviewer error and bias could not be ruled out.
The quality of included trials was assessed using an appropriate tool, but it was unclear whether the results of quality assessment were used in the synthesis of results. The decision to pool trial results statistically was justified given the lack of evidence of heterogeneity. The authors acknowledged the limitations of small sample sizes of included trials.
The authors' conclusions reflected the evidence presented, but should be interpreted with caution given the potential for publication bias, reviewer error and bias and the limitations of small sample sizes.