At what age should lead screening begin in children?

Lead Screening in Children: When to Begin

Lead screening should begin at 12 months of age, with repeat testing at 24 months for all children enrolled in Medicaid or those identified as high-risk, and screening of previously untested children aged 36-72 months. 1

Standard Screening Ages

Universal Medicaid Requirements

• All children enrolled in Medicaid must receive blood lead screening at ages 12 and 24 months. 1, 2
• Children aged 36-72 months who have not been previously screened must also receive testing. 1
• This is a federal requirement with no waiver option—risk assessment questionnaires cannot substitute for actual blood lead testing in this population. 1

Non-Medicaid Children

• Follow state or local screening plans if available, which may recommend either universal or targeted screening based on community-wide data. 1
• In areas lacking a state or local screening plan, the CDC recommends blood lead testing for all children at ages 1 and 2 years, plus screening at ages 36-72 months if not previously tested. 1

Rationale for Two Screenings at Ages 1 and 2 Years

Two separate screenings are essential because lead exposure changes dynamically during early childhood. 1

• Lead exposure peaks at 18-24 months as children become more mobile and reach window sills or other contaminated surfaces. 1
• Among high-risk children in Chicago with blood lead levels <10 µg/dL at age 1 year, 21% developed elevated levels (>10 µg/dL) by age 2 years. 1
• External factors such as family relocation or home remodeling can introduce new exposures between screenings. 1

Earlier or More Frequent Screening in High-Risk Areas

Some jurisdictions recommend more intensive screening protocols: 1, 3

• Starting at 6-9 months in high-risk areas (e.g., Chicago, New York City, Philadelphia). 1, 3
• Every 6 months for children <2 years in high-risk settings. 3, 2
• More rapid follow-up for children <12 months with blood lead levels 6-9 µg/dL. 1

High-Risk Criteria Requiring Targeted Screening

Children should be screened if they have any of these risk factors: 3, 2

• Housing built before 1960 (especially pre-1940 homes, which have 68% lead hazard prevalence). 3, 4
• Recent home renovations or repairs within the past 6 months. 3, 2
• Parental occupational exposures with potential take-home contamination. 3, 2
• Use of imported spices, cosmetics, folk remedies, pottery, or cookware. 3, 2
• Siblings with elevated blood lead levels. 2
• Developmental delays of unknown etiology. 2

Important Caveats

Risk Assessment Questionnaires Are Inadequate

• Risk assessment questionnaires have poor sensitivity (typically identifying only 62-75% of children with elevated levels) and should not replace blood testing in high-risk populations. 2, 5
• Even with optimized questions, the majority of children in low-risk areas still require blood lead testing when using questionnaire-based targeting. 5

No Safe Threshold Exists

• Blood lead levels <5 µg/dL are associated with decreased IQ, academic achievement, and neurodevelopmental problems. 3, 4, 6
• The CDC reference value is now 3.5 µg/dL (97.5th percentile), though many guidelines still reference 5 µg/dL. 3
• Primary prevention through environmental remediation is most effective, as no treatments reverse developmental effects once exposure has occurred. 3, 4, 6

Testing Methodology Matters

• Use venous blood sampling when possible, as capillary samples can be contaminated by lead on skin surfaces. 3, 2
• Any elevated capillary result must be confirmed with venous blood. 2, 4
• Select laboratories achieving routine performance within ±2 µg/dL rather than the federally permitted ±4 µg/dL. 3, 4

Screening Beyond Age 3 Years

• While most screening focuses on children <3 years, some children develop elevated levels after age 3, particularly in high-risk communities. 7, 8
• However, universal screening beyond age 3 is not warranted in most communities, as the majority of new elevations after age 3 are borderline (10-12 µg/dL) and often revert to normal on repeat testing. 7
• Children with blood lead levels 7-9 µg/dL before age 2 and black children remain at higher risk for developing elevated levels after age 3. 8