Table 1.

Description and examples of the Cochrane Collaboration’s seven domains [6,7].

Domain	Type of Bias Addressed	Description	Example of Low Risk Characteristics	Example of High Risk Characteristics
Random Sequence Generation	Selection Bias	Addresses whether there were sufficient information describing the method used by the RCT to generate the allocation sequence.	Random number tables Use of an electronic random number generator	Sequence generation by date of birth Sequence generation by rule based on date of admission
Allocation Sequence Concealment	Selection Bias	Addresses whether there were sufficient information describing the method used to mask the allocation sequence.	Central allocation Use of sealed envelopes	Using an open random allocation
Blinding of Participants and Personnel	Performance Bias	Describes whether the participants and personnel were unaware of the interventions that the participants received.	Clear statement of blinding/masking participants and personnel.	No blinding/incomplete blinding
Blinding of Outcome Assessment	Detection Bias	Describes measures used to blind outcome assessors to interventions that the participants received.	Clear statement of blinding/masking of outcome assessors	No blinding of outcome assessment
Incomplete Outcome Data	Attrition Bias	Describes the completeness of outcome data for each major outcome.	No missing outcome data	Significant missing outcome data, which likely is related to true outcome
Selective Outcome Reporting	Reporting Bias	Describes reporting of all primary and secondary outcomes discussed within the introduction or methods section of the RCT.	All of the study’s pre-specified outcomes are reported	Some of the study’s pre-specified outcomes are missing
Other Sources of Bias		State any important concerns about validity of the study not addressed elsewhere.	-	Poor study design