Background: In 2006, the U.S. Preventive Services Task Force (USPSTF) found insufficient evidence to recommend for or against routine screening for elevated blood lead levels in asymptomatic children ages 1 to 5 years who are at increased risk for lead poisoning (I recommendation), and recommended against routine screening in those at average risk (D recommendation).
Purpose: To synthesize evidence on the effects of screening, testing, and treatment for elevated blood lead levels in children age 5 years and younger in the primary care setting, to update a prior USPSTF review on screening for elevated blood lead levels in childhood.
Data Sources: Cochrane CENTRAL and Cochrane Database of Systematic Reviews (through June 2018), and Ovid MEDLINE (1946 to June 2018), reference lists, and surveillance through December 5, 2018.
Study Selection: English-language trials and observational studies of screening effectiveness, test accuracy, and benefits and harms of screening and interventions in asymptomatic children age 5 years and younger.
Data Extraction: One investigator abstracted details about study design, patient population, setting, screening method, followup, and results. Two investigators independently applied prespecified criteria to rate study quality using methods developed by the USPSTF. Discrepancies were resolved through consensus.
Data Synthesis (Results): A total of 22 studies were included in this review (N=10,449). No studies directly evaluated clinical benefits or harms of screening versus not screening children for elevated blood lead levels. More than one positive answer on the five-item 1991 Centers for Disease Control and Prevention screening questionnaire was associated with a pooled sensitivity of 48 percent (95% confidence interval [CI], 31.4% to 65.6%) and specificity of 58 percent (95% CI, 39.9% to 74.0%) for identifying children with a venous blood level greater than 10 µg/dL (5 studies; N=2,265). Adapted versions of the questionnaire did not demonstrate improved accuracy. Capillary blood lead testing demonstrated sensitivity of 87 to 91 percent and specificity greater than 90 percent, compared with venous measurement (4 studies; N=1,431). Counseling and nutritional interventions or residential lead hazard control techniques did not reduce blood lead concentrations in asymptomatic children, but studies were few and had methodological limitations (7 studies; N=1,419). A trial of dimercaptosuccinic acid chelation therapy found reduced blood lead levels in children at 1 week to 1 year but not at 4.5 to 6 years (N=780), while another trial found no effect at 1 and 6 months (N=39). Seven-year followup assessments showed no effect on neuropsychological development; a small deficit in linear growth (height difference at 7 years in treated patients, 1.17 cm [95% CI, 0.41 to 1.93 cm]) and poorer cognitive outcomes reported as the Attention and Executive Functions subscore of the Developmental Neuropsychological Assessment (unadjusted difference, −1.8 [95% CI, −4.5 to 1.0]; adjusted P=0.045) in children treated with dimercaptosuccinic acid chelation.
Limitations: Limited to English-language articles; quality and applicability of studies were limited due to study design, poor reporting of statistical outcomes, and loss to followup. Studies were lacking on the effectiveness of screening or treatments in reducing elevated blood lead levels or improving health outcomes in children. There was no direct evidence on the harms of screening children for elevated blood lead levels.
Conclusions: Evidence on the benefits and harms of screening children for elevated blood lead levels is lacking. Screening questionnaires are not accurate for identifying children with elevated blood lead levels. Capillary blood testing is slightly less accurate than venous blood testing for identification of elevated blood lead levels. Treatment studies of chelating agents, often combined with environmental or household interventions, were not associated with sustained effects on blood lead levels but were associated with harms.