3.2 Risk of bias assessment
Both randomised trials were assessed to have an overall low risk of
bias. Performance and attrition bias were the two domains that the two
trials had a common rating on low risk of bias. (31, 32) One trial had a
high risk of bias for concealment of treatment allocation, as study
sites became aware they were crossing over to the intervention phase
four weeks prior. (31) The other RCT had a high risk of bias for method
of randomisation, as the text did not state how participants were
randomised. (32) Detection bias and reporting bias were judged as
unclear due to a lack of information. The non-RCTs studies were not
given an overall risk of bias as these observational studies were
abstracts only and insufficient information was available to assess most
domains. (27, 28) A summary of risk of bias for all studies is reported
in Table 3.