Table 1.

Checklist for sources of internal bias†

Question	Yes/no/unclear	Description
Selection bias
Subjects in different intervention groups recruited from same populations?
Subjects in different intervention groups recruited over same time periods?
Inclusion and exclusion criteria clear?
Randomization used?
Adequate allocation concealment?
Comparable baseline characteristics?
Adequate adjustment for confounding? [In observational studies only]
Does extent of selection bias depend on magnitude of intervention effect?
Performance bias
Subjects blinded?
Care givers blinded?
Did subjects receive their assigned (or reputedly received) interventions?
Does extent of performance bias depend on magnitude of intervention effect?
Attrition bias
Are the results unlikely to be affected by losses to follow-up?
Are the results unlikely to be affected by post hoc exclusions?
Does extent of attrition bias depend on magnitude of intervention effect?
Detection bias
Outcome assessors blinded?
Outcome measured accurately?
If the results were back-calculated from a reported analysis, was the statistical analysis appropriate?
Does extent of detection bias depend on magnitude of intervention effect?
Other bias suspected
Does extent of other bias depend on magnitude of intervention effect?

†The empty areas are to be completed.