The review addressed a clear question using appropriate inclusion criteria. Attempts to identify relevant studies were undertaken by searching electronic databases, but it appeared that no search was made for unpublished studies, and the restriction to searching for studies in English meant that some relevant studies may have been missed. It was not clear that suitable methods (e.g. independent, duplicate assessments) were employed to reduce the risks of reviewer error and bias for the processes of study selection and data extraction.
Although it was unclear whether or not a formal assessment of study quality was made, the authors did discuss key quality issues and reported that quality was generally low. A narrative synthesis appeared appropriate considering the evident clinical or methodological heterogeneity.
The authors' conclusions reflected the evidence presented, but the basic search for studies, coupled with the use of limited review processes (or limited reporting of the processes), means their reliability is uncertain.