The review addressed a clear question. Inclusion criteria were defined. The literature search was adequate for published studies, but restriction of the review to studies published in certain language raised the possibility of language and publication biases. Appropriate steps were taken to minimise bias and errors when assessing study quality and extracting data; it was unclear whether such steps were also taken when assessing study eligibility.
A formal quality assessment was reported to have been undertaken, but results were reported simply as all studies being of good quality without details on how this summary rating was achieved. Individual study details were lacking and so it was not possible to determine the generalisability of the review findings. Methods used to pool data appeared appropriate.
The authors conclusions are supported by the data but should be interpreted with some caution due to the possibility of publication bias and lack of details on study quality and other study characteristics.