Data collection and analysis
For methods used in the previous update, please see Basevi 2000.
For this update, no new studies were identified from the updated
search.However, full risk of bias was performed and the quality of
the evidence was assessed using theGRADE approach for all of the
currently included studies as described below. In future updates,
we will use the full methods outlined in Appendix 1.
Selection of studies
Two review authors independently assessed for inclusion all the
potential studies we identified as a result of the search strategy.We
resolved any disagreement through discussion.
Data extraction and management
We designed a formto extract data. For eligible studies, two review
authors extracted the data using the agreed form. We resolved
discrepancies through discussion. We entered data into Review
Manager software (RevMan 2014) and checked for accuracy.
Assessment of risk of bias in included studies
Two review authors independently assessed risk of bias for each
study using the criteria outlined in the Cochrane Handbook for
Systematic Reviews of Interventions (Higgins 2011) and resolved
any disagreements by discussion.