Table 2.

Summary of the evidence for interventions to reduce publication bias

Intervention	Number of studies	Summary of evidence	Quality of evidencea
Research sponsors' guidelines	None	No evidence located
Prospective trial registration	30 Studies	The use of trial registries has increased since implementation of the ICMJE policy in 2005	Moderate
		Selective outcome-reporting bias persists in 30–65% of published reports of trials despite registration	Low
		In approximately 50% of registry entries, it is not possible for readers/reviewers to detect outcome-reporting bias due to missing information	Low
Mandatory to enter trial outcome/results data in registry	1 Study	Only 22% of pediatric trials subject to the FDA Amendment Act 2007 had entered results after 12 months; however, only 10% of trials not subject to the act had results.	Very low
Right to publication	None	No evidence located
Peer review	2 Studies	Blinding peer reviewers reduces geographical bias against non-US authors	Very low
Disclosure of conflict of interest	5 Studies	Between 8% and 29% of authors did not reveal any conflict and up to two-thirds did not fully reveal their financial conflicts of interest	Low
Electronic publication	None	No evidence located
Open access	1 Study	Open-access publishing does not increase geographical bias against authors from LMIC	Very low

Abbreviations: ICMJE, International Committee of Medical Journal Editors; FDA, Food and Drug Administration; LMIC, low- and middle-income countries.

^aQuality of evidence determined using the GRADE system (Grading of Recommendations Assessment, Development and Evaluation).