When should an infant be screened for lead exposure (blood lead level), and which risk factors require earlier testing?

When to Screen Infants for Lead Exposure

All infants should receive blood lead screening at 12 months and again at 24 months of age if they are enrolled in Medicaid or live in high-risk areas, with additional testing at 36-72 months if never previously screened. 1

Universal Screening Requirements

Medicaid-Enrolled Children

• Mandatory testing at 12 months and 24 months for all children enrolled in Medicaid—this is a federal requirement that cannot be replaced by risk-assessment questionnaires alone. 1
• Children aged 36-72 months who were never previously screened must also be tested. 1

Non-Medicaid Children

• In areas without state or local screening plans, the CDC recommends universal blood lead testing at ages 1 and 2 years, with catch-up testing at 36-72 months if not previously screened. 1
• Follow your state and local requirements, as many jurisdictions mandate more stringent screening than federal guidelines. 2

Targeted Screening for High-Risk Infants

Test children immediately (regardless of age) if they have any of these risk factors: 2

Housing-Related Risk Factors

• Residence in or regular visits to housing built before 1960, especially homes built before 1940 (68% lead hazard prevalence). 2, 3
• Housing that is in poor repair or has undergone renovation, repair, or painting within the past 6 months. 2, 3
• Identified lead hazard in the home or child care facility. 2

Geographic Risk Factors

• Living in communities where ≥25% of housing was built before 1960. 2
• Living in census block groups where ≥5% of children have blood lead levels ≥5 μg/dL. 2

Other High-Risk Exposures

• Immigrant, refugee, or internationally adopted children should be tested upon arrival in the United States. 2
• Parental occupational exposures that could result in take-home contamination. 3
• Use of imported spices, cosmetics, folk remedies, pottery, or cookware. 3
• Siblings with elevated lead levels. 1

Why Two Separate Screenings Are Essential

Testing at both 12 and 24 months is critical because lead exposure changes dynamically during early childhood: 3, 1

• Peak exposure typically occurs at 18-24 months when children become mobile and contact contaminated surfaces like window sills. 1
• Among high-risk children with blood lead levels <10 μg/dL at age 1 year, 21% developed levels >10 μg/dL by age 2 years. 3, 1
• External factors such as family relocation or home remodeling can introduce new lead sources between screenings. 1

Enhanced Screening in High-Risk Settings

Some jurisdictions recommend more intensive screening protocols: 3, 1

• Initiate screening as early as 6-9 months in high-risk areas (e.g., Chicago, New York City, Philadelphia). 1
• Test every 3-6 months for children under 2 years in high-risk settings if risk factors persist or increase. 3
• For infants initially screened before 12 months who are at high risk, retest in 3-6 months as lead exposure may increase with mobility. 3

Proper Testing Methodology

Use venous blood sampling whenever possible—it is the gold standard for lead measurement: 3, 1

• Capillary (fingerstick) samples are prone to skin contamination and should only be used for initial screening. 3, 1
• Any elevated capillary result must be confirmed with venous blood to rule out false positives. 3, 1, 4
• Select laboratories that achieve routine performance within ±2 μg/dL rather than the federally permitted ±4 μg/dL. 3

Special Populations Requiring Screening

Screen all children with developmental delays, regardless of other risk factors: 1

• Blood lead levels <5 μg/dL are associated with decreased IQ, academic achievement, and neurodevelopmental problems. 3, 1, 4
• No safe threshold exists for lead exposure—even very low levels cause harm. 3, 4

Critical Caveats

Risk assessment questionnaires have poor sensitivity and frequently fail to identify children with elevated blood lead levels—maintain a low threshold for testing any child with potential exposure. 3, 1

Primary prevention is most effective, as no treatments reverse the developmental effects of lead toxicity once exposure has occurred. 3, 4

The current CDC reference value is 3.5 μg/dL (representing the 97.5th percentile), though the 2016 AAP guidelines still reference 5 μg/dL as the action level. 3, 4