Study selection
Two subject experts (GE/E-JP to 15 March 2011 and
GE/RB updated to 30 September 2011) searched information
sources independently and assessed identified
studies for inclusion, facilitated by grading each criterion
(table 1) as eligible/not eligible/might be
eligible.20 The full text of a study was reviewed and the
study considered potentially relevant when it could not
be clearly excluded on the basis of its Title and
Abstract19 following discussion between the two independent
reviewers. Full text was obtained for abstracts
with insufficient information or in a situation of
disagreement. A study was included when both reviewers
independently assessed it as satisfying the inclusion
criteria from the full text. A third reviewer (AR, methodological
and subject expert) mediated in the event of
disagreement following discussion.16
Risk of bias for each included trial was independently
assessed by the same initial reviewers. Consistent with
Cochrane,17 risk of bias and homogeneity of participants,
interventions and outcome measures were important
considerations informing potential inclusion of trials in
meta-analyses, thereby ensuring meaningfulness of findings
from a clinical perspective. The third reviewer
mediated in situations of disagreement.16 Cohen’s k was
used to assess agreement between reviewers.21 All tools
and processes were piloted prior to use.