| Key Question | Findings |
| Children |
| KQ 1:
Is there direct evidence that screening for lead results in improved health outcomes (i.e. cognitive changes, behavioral problems, learning disorders)? | There is no direct evidence from controlled studies of screening. |
| KQ 2:
What is the prevalence of elevated lead in children? | The prevalence of blood lead >10 µg/dL among children aged 1-5 years in the U.S. has declined from 9% in 1988-1991 to 1.6% 1999-2002. |
| KQ 2: Are there population-level risk factors that identify children at higher risk for elevated lead levels? | Population-level risk factors among children include age <5 years; urban residence; low income; low parental educational attainment; pre-1950 housing; and recent immigration. Mean blood levels among African-American children remain significantly higher than Mexican American children and non-Hispanic whites. |
| KQ 3.:
Can screening tests accurately detect elevated blood lead levels? | Blood lead concentration is more sensitive and specific than free erythrocyte proptoporphyrin (EP) levels, but can be affected by environmental lead contamination and laboratory analytic variation. In one study of 47,230 suburban and rural children, 4.7% had an elevated EP level, while only 0.6% had elevated BLL. Capillary sampling has false-positive rates of 3-9%, and false-negative rates of 1-8%, compared with venous blood lead levels. |
| KQ 3: How accurate are questionnaires (or other tools) for risk factor assessment at various blood lead levels? | The sensitivity and specificity of questionnaires vary considerably with the prevalence of EBLL in the population surveyed and the cutoff BLL (10 vs. 15 µg/dL). One study found that rental status, lead-contaminated floor dust, and poor housing condition were associated with EBLL, suggesting that housing characteristics can be used to identify homes where a lead hazard may exist before or during occupancy. |
| KQ 3: What is the optimal frequency for screening? |
Not addressed in this review. |
| KQ 3:
What is the optimal frequency for repeat testing? |
Not addressed in this review. |
| KQ 5:
Do interventions for elevated lead levels result in improved health outcomes or lead levels? | We identified no evidence that treatment, lead abatement, or education improved neurocognitive outcome in asymptomatic children with mildly-moderately increased lead levels. In one trial of succimer there was no benefit or slight harm. Some interventions have small, inconsistent, or unsustained effects on lead levels in high-risk children. |
| KQ 4, KQ 6.:
What are the adverse effects of screening and treatment? | Go to Adverse Effects of Screening and Intervention in the Summary text. |
| KQ 7.:
What are cost effectiveness issues? | Not addressed in this review. |
| Pregnant Women |
| KQ 1.:
Is there direct evidence that screening in asymptomatic pregnant women for lead results in improved health outcomes? | There is no direct evidence from controlled studies of screening that screening improves maternal hypertension, cognitive changes in offspring or perinatal outcomes. |
| KQ 2:
What is the prevalence of elevated lead in pregnant women? | In 1992, two large surveys of low-income pregnant women found 0% and 6% with blood levels >15 µg/dL. A longitudinal study of pregnant women in Boston found that umbilical cord blood levels declined 82% between 1980 and 1990. |
| KQ 2: Are there population-level risk factors that identify pregnant women at higher risk for elevated lead levels (i.e., geography, racial/ethnicity, SES, age)? | Ethnic background, country of origin, and immigrant status of birth mothers have been shown to be associated with prenatal lead exposure in newborns. Cigarette smoking, maternal age, and alcohol intake have been found to increase umbilical cord blood lead levels. |
| KQ 3:
Can screening tests accurately detect elevated blood lead levels? | Blood lead concentration is more sensitive and specific than free erythrocyte proptoporphyrin (EP) levels, but can be affected by environmental lead contamination and laboratory analytic variation. In one study of 47,230 suburban and rural children, 4.7% had an elevated EP level, while only 0.6% had elevated BLL. Capillary sampling has false-positive rates of 3-9%, and false-negative rates of 1-8%, compared with venous blood lead levels. |
| KQ 3: How accurate are questionnaires (or other tools) for risk factor assessment at various blood lead levels? | We found one study of a 4-question prenatal survey developed by the Centers for Disease Control and Prevention (CDC) that had a sensitivity of 75.7%, and a negative predictive value of 93.1%. |
| KQ 3: What is the optimal frequency for screening? What is the optimal frequency for repeat testing? | Not addressed in this review. |
| KQ 5.:
Do interventions for elevated lead levels result in improved health outcomes? | We identified no evidence that treatment, lead abatement, or education improved neurocognitive outcome in asymptomatic children with mildly-moderately increased lead levels. In one trial of succimer there was no benefit or slight harm. |
| KQ 4, KQ 6.:
What are the adverse effects of screening and treatment? | Go to Adverse Effects of Screening and Intervention in the Summary text. |
| KQ 7.:
What are cost effectiveness issues? | Not addressed in this review. |
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