Synthesis of results
The certainty of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach.11Guyatt G, Oxman AD, Akl EA, Kunz R, Vist G, Brozek J, Norris S, Falck-Ytter Y, Glasziou P, DeBeer H, Jaeschke R, Rind D, Meerpohl J, Dahm P, Schünemann HJ. GRADE guidelines: 1. Introduction-GRADE evidence profiles and summary of findings tables. Journal of clinical epidemiology. 2011;64(4):383-394.
Small groups of clinicians and methodologists reviewed studies about each intervention and created evidence profiles (all authors). Authors were not involved in decisions about topics where they had a potential conflict. All taskforce members decided on the conclusions by consensus.
Results were summarised using narrative synthesis. We did not undertake meta-analysis because the minimum criteria for meta-analysis set out in the review protocol were not met.
We used standardised GRADE statements to narratively indicate the effect size and the certainty of the evidence (Table 1).22Santesso N, Glenton C, Dahm P, Garner P, Akl EA, Alper B, Brignardello-Petersen R, Carrasco-Labra A, De Beer H, Hultcrantz M, Kuijpers T, Meerpohl J, Morgan R, Mustafa R, Skoetz N, Sultan S, Wiysonge C, Guyatt G, Schünemann HJ. GRADE guidelines 26: informative statements to communicate the findings of systematic reviews of interventions. J Clin Epidemiol 2020;119:126-135. For example, if the certainty of evidence was very low, regardless of effect size, the following terminology was used: ‘It is unclear whether [intervention] affects [outcomes] because the evidence is very uncertain.”