Screening for Elevated Blood Lead Levels in Childhood and Pregnancy

Abstract

ImportanceElevated blood lead level is associated with serious, often irreversible, health consequences.ObjectiveTo synthesize evidence on the effects of screening, testing, and treatment for elevated blood lead level in pregnant women and children aged 5 years and younger in the primary care setting to inform the US Preventive Services Task Force.Data SourcesCochrane CENTRAL and Cochrane Database of Systematic Reviews (through June 2018) and Ovid MEDLINE (1946 to June 2018); surveillance through December 5, 2018.Study SelectionEnglish-language trials and observational studies of screening for and treating elevated lead levels in asymptomatic children and pregnant women.Data Extraction and SynthesisIndependent critical appraisal and data abstraction by 2 reviewers using predefined criteria.Main Outcomes and MeasuresElevated blood lead level, morbidity, mortality, clinical prediction tools, test accuracy, adverse events.ResultsA total of 24 studies (N = 11 433) were included in this review. No studies evaluated the benefits or harms of screening vs no screening in children. More than 1 positive answer on the 5-item 1991 Centers for Disease Control and Prevention (CDC) screening questionnaire was associated with a pooled sensitivity of 48% (95% CI, 31.4% to 65.6%) and specificity of 58% (95% CI, 39.9% to 74.0%) for identifying children with a venous blood lead level greater than 10 μg/dL (5 studies [n = 2265]). Adapted versions of the CDC questionnaire did not demonstrate improved accuracy. Capillary blood lead testing demonstrated sensitivity of 87% to 91% and specificity greater than 90%, compared with venous measurement (4 studies [n = 1431]). 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 = 1419]). One trial (n = 780) of dimercaptosuccinic acid (DMSA) chelation therapy found reduced blood lead levels in children at 1 week to 1 year but not at 4.5 to 6 years, while another trial (n = 39) found no effect at 1 and 6 months. Seven-year follow-up assessments showed no effect on neuropsychological development, a small deficit in linear growth (height difference, 1.17 cm [95% CI, 0.41 to 1.93]), 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 = .045) in children treated with DMSA chelation. Evidence was too limited to determine the accuracy of screening questionnaires or benefits and harms of treatment in pregnant women.Conclusions and RelevanceScreening questionnaires were not accurate for identifying children with elevated blood lead levels. Chelating agents in children were not significantly associated with sustained effects on blood level levels but were associated with harms.