Table 5.

Guiding questions by domain.

	Domain	Guiding question
1	Bias in selection of participants into the study (see Table 4 for description of biases)	Could the exposure status (or level) assessed (or assigned) in the study sample not represent exposure in the target population?
2	Bias due to a lack of blinding of study personnel	Could study personnel have known the exposure status (or level) or other characteristics of study participants and, if yes, could this knowledge have influenced how they conducted the exposure assessment?
3	Bias due to exposure misclassification	Could the methods used for assessing (or assigning) exposure have over- or under-estimated exposure?
4	Bias due to incomplete exposure data	Could data on exposure status (or level) be incomplete for eligible participants?
5	Bias due to selective reporting of exposures	Could relevant exposures or exposure categories be selectively not reported?
6	Bias due to conflict of interest	Could the study and/or one or more study authors have received support from entities with potential interests in the exposure assessed (or assigned)?
7	Bias due to differences in numerator and denominator	Could the definition and/or counting of persons contributing to the numerator differ from those contributing to the denominator in the ratio used to estimate prevalence?
8	Other bias	Could the study have other problems that could have introduced bias?