The review addressed a clear question and was supported by reproducible eligibility criteria. Attempts to identify relevant studies in any language were undertaken by searching electronic databases and checking references. It was unclear whether or not unpublished studies were sought (only published studies were included in the analyses). Suitable methods appear to have been used to reduce the risk of reviewer error and bias throughout the review.
The review had some limitations. The quality assessment results were not reported in detail, which made it difficult to evaluate the reliability of individual trial results. Heterogeneity was addressed only by use of a random effects meta-analysis; no subgroup or sensitivity analyses were reported. Nevertheless, the direction of effect was the same in nearly all trials for the statistically significant analyses.
Notwithstanding some limitations, the authors' conclusions appear reasonable and their call for a further trial seems warranted.