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).