Certainty (or confidence) in the body of evidence for an
outcome
We downgraded the evidence from high certainty to moderate, low or very
low certainty for serious or very serious study limitations (risk of
bias), indirectness and inconsistency of evidence, imprecision of effect
estimates or potential publication bias using the guidance developed by
the Cochrane Handbook (Higgins 2011), and the GRADE working group
(Atkins 2004).