Appendix 1.  Key Questions and Critical Key Questions

Members of the U.S. Preventive Services Task Force (USPSTF) and Agency for Healthcare Research and Quality (AHRQ) identified an analytic framework (Figure 1, 20 KB) and key questions (KQs) for updating the USPSTF guidelines for lead screening.

Key Questions for Children Were Stated as Follows:

• KQ 1: Is there direct evidence that screening for lead results in improved health outcomes (i.e. cognitive changes, behavioral problems, learning disorders)?
• KQ 2: What is the prevalence of elevated lead in children?  Are there population-level risk factors that identify children at higher risk for elevated lead levels (i.e., geography, race/ethnicity, socioeconomic status, age)?
• KQ 3:  Can screening tests accurately detect elevated blood lead levels?  What is the accuracy of using questionnaires (or other tools) for risk factor assessment at various blood lead levels?  What is the optimal frequency for screening?  What is the optimal frequency for repeat testing?
• KQ 4:  What are the adverse effects of screening?
• KQ 5:  Do interventions (i.e. counseling families to reduce lead exposure, nutritional interventions, residential lead hazard control techniques, chelation therapy) for elevated lead levels result in improved health outcomes?
• KQ 6:  What are the adverse effects of interventions?
• KQ 7:  What are cost effectiveness issues?

Key Questions for Pregnant Women were Stated as Follows:

• KQ 1:  Is there direct evidence that screening in asymptomatic pregnant women for lead results in improved health outcomes (i.e. cognitive changes in offspring, perinatal outcomes including birth weight/preterm delivery etc, maternal blood pressure)?
• KQ 2:  What is the prevalence of elevated lead in asymptomatic pregnant women?  Are there population-level risk factors that identify pregnant women at higher risk for elevated lead levels (i.e. geography, racial/ethnicity, SES, age)?
• KQ 3:  Can screening tests accurately detect elevated blood lead levels?  What is the accuracy of using questionnaires (or other tools) for risk factor assessment at various blood lead levels?
• KQ 4:  What are the adverse effects of screening?
• KQ 5:  Do interventions (i.e. counseling families to reduce lead exposure, nutritional interventions, residential lead hazard control techniques, chelation therapy) for elevated lead levels result in improved health outcomes?
• KQ 6:  What are the adverse effects of the interventions?
• KQ 7:  What are cost effectiveness issues?

Members of the USPSTF and AHRQ identified KQs 1 and 5 for children and pregnant women as critical key questions.  For these critical key questions, we used USPSTF methods to systematically abstract information about the design, results, and internal validity of each study, and included only those studies we rated fair-quality or better.²  We conducted a selected review of the literature that addressed KQs 2, 3, 4, and 6.  The cost-effectiveness of screening would be examined only in the presence of adequate evidence of intervention efficacy. We did not examine KQ 7 because of the lack of evidence of improved clinical outcomes for KQ 5. We reviewed the populations of asymptomatic children and pregnant women separately.

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