"A systematic review attempts to collate all empirical evidence that fits pre-specified eligibility criteria in order to answer a specific research question. It uses explicit, systematic methods that are selected with a view to minimizing bias, thus providing more reliable findings from which conclusions can be drawn and decisions made (Antman 1992, Oxman 1993). The key characteristics of a systematic review are:
A clearly stated set of objectives with pre-defined eligibility criteria for studies;
An explicit, reproducible methodology;
A systematic search that attempts to identify all studies that would meet the eligibility criteria;
An assessment of the validity of the findings of the included studies, for example through the assessment of risk of bias; and
