Screening Children for Lead Poisoning

Screening for lead can be universal or targeted.  Screening can be directed at identifying lead-exposed individuals or populations, or it can be used to identify lead contaminated environments.  Decisions about the approach to screening is based on knowledge of the distribution of lead in the population or the environment and the availability of resources to manage lead-exposed individuals or lead-contaminated environments.  Identifying lead-exposed populations or individuals is not a substitute for primary prevention.

Universal screening of children with a blood lead level at ages 1 and 2 years is warranted in several situations.  These include where the prevalence is sufficiently high enough to warrant universal screening.  In the United States, the American Academy of Pediatrics set criteria for continued universal screening by BLL testing include a prevalence of elevated levels of more than 11% or if more than 26% of the housing was built prior to 1959 (the main source of lead exposure in the United States is from lead-based paint) (AAP, 2005).  This policy has been recently revised to recommend universal screening for all medicaid-eligible children (AAP, 2005).  Otherwise, blood sampling may be targeted at selected populations based on local risk assessment of lead exposure as determined by local health authorities.  However, well-validated tools for screening with risk factor questions do not currently exist (Binns, 1999).  High risk that necessitates blood lead testing includes residence in a geographic area known to have large amounts of lead or membership in a high-risk group such as indigent, urban, minority children. However, in the absence of formal local guidance, universal screening should be undertaken. Thus, if epidemiologic or housing age data are unavailable for a geographic area, all children should be screened by blood lead measurement at ages 1 and 2 years and at 36 to 72 months of age if not screened previously. Where local risk has been defined and found to be low, the need for blood lead testing is based on the results of individual risk assessment(Markowitz 2000).

Children are screened at 1 and 2 years with a blood lead level since the normal, developmentally appropriate behaviors which put them at greatest risk for exposure, hand-to-mouth, eating the same diets as their parents and pica begin at different times for each individual child.  Blood lead levels peak between age 1 and 2 years.  Targeted screening is continued until at least the age of 7 as children may move, parents may change their occupation.  Continued targeted screening should be considered into adulthood as new factors arise, such as occupational hazards, hobbies that put them at risk and moving to new environments which may be lead-contaminated.

At each health supervision visit, a very brief personal risk questionnaire, tailored to the local risk factors, may be used as initial screening. If answers indicate risk, BLLs should be measured. Unfortunately, the overall sensitivity of questionnaires designed to identify lead poisoning in children is about 60% to 70%. Sensitivity can be improved when local conditions are considered and appropriate questions added. For example, adding the question, “Do you live near the town’s battery factory or metal smelter?” may improve the sensitivity. Such additions require an intimate knowledge of the environment in the catchment area of the clinical practice. Questionnaires should be available in the primary languages of the local residents (Markowitz 2000).