2. Investigation of heterogeneity
If inconsistency was high, we have reported this. First we investigated
whether data had been entered correctly. Second, if data
had been correct, we visually inspected the graph and successively
removed studies outside of the company of the rest to see if heterogeneity
was restored. Should this occur with no more than 10%of
the data being excluded, we have presented data. If not, we have
not pooled data and discussed issues.
Should unanticipated clinical or methodological heterogeneity be
obvious we simply stated hypotheses regarding these for future reviews
or versions of this review. We pre-specify no characteristics
of studies thatmay be associated with heterogeneity except quality
of trial method. If no clear association could be shown by sorting
studies by quality of methods, we have performed a randomeffects
meta-analysis. Should another characteristic of the studies
be highlighted by the investigation of heterogeneity, perhaps some
clinical heterogeneity not hitherto predicted but plausible causes
of heterogeneity, we have discussed these post hoc reasons, and
analyse and present the data. However, should the heterogeneity
be substantially unaffected by use of random-effects meta-analysis
and no other reasons for the heterogeneity be clear, we have presented
the final data without a meta-analysis.