Table 6.

Potential steps in the quality assessment of a body of evidence of prevalence studies.

Step	Use in existing approaches (step)	Use in QoE-SPEO (step)	Use of the step in QoE-SPEO
Judge the level of expected heterogeneity	No	Yes (Step 1)	Step 1 in QoE-SPEO was developed specifically for the approach. The results of the assessment of the level of expected heterogeneity conducted in Step 1 are the basis for QoE-SPEO’s Step 2.
Determine the baseline quality of evidence rating	Yes (first step) a	No	This step is not used in QoE-SPEO. We did not consider features of study designs to centrally determine quality of evidence in a body of prevalence studies. All QoE-SPEO assessments start at “high quality” of evidence.
Assess downgrade domains	Yes (second step)	Yes (Step 2)	Step 2 in QoE-SPEO was adopted from the second step in existing approaches.
Assess upgrade domains	Yes (third step)	No	This step is not used in QoE-SPEO, because we did not identify any relevant upgrade domains.
Reach a final decision (rating) on the quality of evidence	Yes (fourth step)	Yes (Step 3)	Step 3 in QoE-SPEO was adopted from the fourth step in existing approaches.

Footnotes: ^a Not a step in GRADE. QoE-SPEO – Quality of Evidence in Studies estimating Prevalence of Exposure to Occupational risk factors