Blood Lead Levels: Screening -- Children 1-5, Increased Risk


General

Grade: I

Specific Recommendations

The USPSTF concludes that evidence is insufficient to recommend for or against routine screening for elevated blood lead levels (BLLs) in asymptomatic children aged 1 to 5 who are at increased risk.

Frequency of Service

No information available.

Risk Factor Information

Children under 5 years of age are at greater risk for elevated BLLs and lead toxicity because of increased hand-to-mouth activity, increased lead absorption from the gastrointestinal tract, and the greater vulnerability of the developing central nervous system. Risk factors for increased BLLs in children and adults include minority race/ethnicity; urban residence; low income; low educational attainment; older (pre-1950) housing; recent or ongoing home renovation or remodeling; pica exposure; use of ethnic remedies, certain cosmetics, and exposure to lead-glazed pottery; occupational and paraoccupational exposures; and recent immigration.


Clinical

  • This USPSTF recommendation addresses screening for elevated BLLs in children aged 1 to 5 years who are at both average and increased risk and in asymptomatic pregnant women.

  • The highest mean blood lead level in the United States occurs in children aged 1 to 5 years (geometric mean: 1.9 µg/dL). Children under 5 years of age are at greater risk for elevated BLLs and lead toxicity because of increased hand-to-mouth activity, increased lead absorption from the gastrointestinal tract, and the greater vulnerability of the developing central nervous system. Risk factors for increased BLLs in children and adults include minority race/ethnicity; urban residence; low income; low educational attainment; older (pre-1950) housing; recent or ongoing home renovation or remodeling; pica exposure; use of ethnic remedies, certain cosmetics, and exposure to lead-glazed pottery; occupational and paraoccupational exposures; and recent immigration. Additional risk factors for pregnant women include alcohol use, smoking, pica, and recent immigration status.

  • BLLs in childhood, after peaking at 2 years of age, decrease during short-term and long-term follow-up without intervention. Most lead is stored in bone. High bone lead levels can be present with normal BLLs, so that BLLs often do not reflect the total amount of lead in the body. This could explain the lack of effect of BLL-lowering measures on reducing neurotoxic effects.

  • Screening tests for elevated BLLs include free erythrocyte (or zinc) protoporphyrin levels and capillary or venous BLLs. Erythrocyte (or zinc) protoporphyrin is insensitive to modest elevations in BLLs and lacks specificity. Blood lead concentration is more sensitive than erythrocyte protoporphyrin for detecting modest lead exposure, but its accuracy, precision, and reliability can be affected by environmental lead contamination. Therefore, venous BLL testing is preferred to capillary sampling. Screening questionnaires may be of value in identifying children at risk for elevated BLLs but should be tailored for and validated in specific communities for clinical use.

  • Treatment options in use for elevated BLLs include residential lead hazard-control efforts (ie, counseling and education, dust or paint removal, and soil abatement), chelation, and nutritional interventions. In most settings, education and counseling are offered for children with BLLs from 10 to 20 µg/dL. Some experts have also recommended nutritional counseling for children with BLLs in this range. Residential lead hazard control is usually offered to children with BLLs greater than or equal to 20 µg/dL, whereas chelation therapy is offered to children with BLLs greater than or equal to 45 µg/dL.

  • Community-based interventions for the primary prevention of lead exposure are likely to be more effective, and may be more cost-effective, than office-based screening, treatment, and counseling. Relocating children who do not yet have elevated BLLs but who live in settings with high lead exposure may be especially helpful. Community, regional, and national environmental lead hazard-reduction efforts, such as reducing lead in industrial emissions, gasoline, and cans, have proven highly effective in reducing population BLLs.

Rationale


Importance
BLLs in children have declined dramatically in the United States over the past 2 decades. However, segments of the population remain at increased risk for higher BLLs. Even relatively low BLLs are associated with neurotoxic effects in children. Severely elevated BLLs in symptomatic pregnant women are associated with poor health outcomes; however, BLLs in this range are rare in the US population.

Detection
There is good evidence that venous sampling accurately detects elevated BLLs and fair evidence that validated questionnaires are modestly useful in identifying children at increased risk for elevated BLLs.

Benefits of Detection and Early Intervention
The USPSTF found good-quality evidence that interventions do not result in sustained decreases in BLLs and found insufficient evidence (no studies) evaluating residential lead hazard-control efforts (ie, dust or paint removal, soil abatement, counseling, or education) or nutritional interventions for improving neurodevelopmental outcomes in children with mildly-to-moderately elevated BLLs. The USPSTF found no studies examining the effectiveness of screening or interventions in improving health outcomes in asymptomatic pregnant women. Given the low prevalence of elevated BLLs in children at average risk and asymptomatic pregnant women, the magnitude of potential benefit cannot be greater than small.

A theoretical benefit of screening is that identification may prevent lead poisoning of other individuals in a shared environment, but the magnitude of this theoretical benefit is uncertain.

Harms of Detection and Early Treatment
There is good-quality evidence that chelation treatment in asymptomatic children does not improve neurodevelopmental outcomes and is associated with a slight diminution in cognitive performance. Chelation therapy may result in transient renal, hepatic, and other toxicity, mild gastrointestinal symptoms, sensitivity reactions, and rare life-threatening reactions. Residential lead-based paint and dust hazard-control treatments may lead to acutely increased BLLs from improper removal techniques. Potential harms of screening are false-positive results, anxiety, inconvenience, work or school absenteeism, and financial costs associated with repeated testing. Although the exact magnitude of these known and potential harms is uncertain, the overall magnitude is at least small.

No studies have directly addressed the harms of screening and interventions for pregnant women. Although there is little specific evidence concerning the potential harms of interventions for pregnant women with elevated BLLs, the magnitude of harms from such interventions is also at least small.

USPSTF Assessment
The USPSTF concludes that the evidence is insufficient to assess the balance between potential benefits and harms of routine screening for elevated BLLs in children at increased risk. Given the significant potential harms of treatment and residential lead hazard abatement, and no evidence of treatment benefit, the USPSTF concluded that the harms of screening for elevated BLLs in children at average risk and in asymptomatic pregnant women outweigh the benefits.


Others

The CDC recommends universal screening in communities where 12% of children aged 1 to 3 years have elevated blood levels, or, in communities that do not have prevalence data, if 27% of the housing was built before 1950. The CDC recommends targeted screening for all other children based on an individual risk assessment, including whether children receive Medicaid, Supplemental Food Program for Women, Infants and Children (WIC), or other forms of governmental assistance. This approach is also supported by the American College of Preventive Medicine. The American Academy of Pediatrics recommends that pediatricians learn whether city or state health departments provide guidance for screening children who are not eligible for Medicaid. If no such guidance is available, the American Academy of Pediatrics recommends that pediatricians consider screening all children. Children should, ideally, be tested at 1 and 2 years of age. The American Academy of Family Physicians recommends screening 12-month-old infants for lead poisoning if they live in communities in which the prevalence of lead levels requiring intervention is high or undefined; if they live in or frequently visit a home built before 1950 that has dilapidated paint or recent or ongoing renovations or remodeling; if they have close contact with a person who has an elevated BLL or who lives near lead industry or heavy traffic; or if they live with someone whose job or hobby involves lead exposure, uses lead-based pottery, or takes traditional remedies that contain lead. Medicaid's Early and Periodic Screening, Diagnostic, and Treatment Program (EPSDT) requires that all children receive a screening blood lead test at 12 and 24 months of age; children between the ages of 36 and 72 months of age must receive a screening blood lead test if they have not previously been screened for lead poisoning. No national organizations currently recommend screening pregnant women for elevated BLLs.


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