This review addressed a clear question and was supported by appropriate inclusion criteria. Adequate attempts were
made to identify relevant studies without language restrictions, which reduced potential for language and publication
biases. The likelihood of publication bias was assessed and found to be absent, but this was based on only a small
number of studies. Two reviewers independently undertook trial selection, data extraction and validity assessment,
which reduced potential for reviewer bias and error. Validity was assessed with published criteria; all studies were of
poor quality. It appeared that appropriate methods were used to pool the trials. Statistical heterogeneity was assessed.
The authors acknowledged that the generalisability of the findings was limited given the small number of studies
included.