Screening for Elevated Blood Lead Levels in Childhood [Entered Retrospectively]

Project Summary Title and Description

Title
Screening for Elevated Blood Lead Levels in Childhood [Entered Retrospectively]
Description
Background: In 2006, the United States Preventive Services Task Force (USPSTF) found insufficient evidence to recommend for or against routine screening for elevated blood lead levels in asymptomatic children aged 1 to 5 who are at increased risk for lead poisoning (I recommendation), and recommended against routine screening for those at average risk (D recommendation). Purpose: To synthesize evidence on the effects of screening, testing, and treatment for elevated blood lead level in children aged five and under in the primary care setting, in order 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, benefits and harms of screening and interventions in asymptomatic children five and under. Data Extraction: One investigator abstracted details about study design, patient population, setting, screening method, follow up, and results. Two investigators independently applied pre specified 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 5-item 1991 Centers for Disease Control and Prevention (CDC) 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 >10µg/dL (5 studies, N = 2,265). Adapted versions of the CDC questionnaire did not demonstrate improved accuracy. Capillary blood lead testing demonstrated sensitivity of 87 percent to 91 percent and specificity >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 (DMSA) chelation therapy found reduced blood lead levels in children at one week to one year but not at 4.5 to 6 years (N = 780), while another trial found no effect at one- and six-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 1.17cm; 95% CI, 0.41 to 1.93); and poorer cognitive outcomes reported as the Attention and Executive Functions sub-score of the Developmental Neuropsychological Assessment (NEPSY) (unadjusted difference -1.8; 95% CI, -4.5 to 1.0, adjusted P = 0.045) in children treated with DMSA 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 follow up. Studies were lacking on the effectiveness of screening or effectiveness of 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 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 levels for identification of elevated blood levels. Treatment studies of chelating agents, often combined with environmental or household interventions, were not associated with sustained effects on blood level levels but were associated with harms.
Attribution
N/A
Authors of Report
N/A
Methodology description
Study Selection: English-language trials and observational studies of screening effectiveness, test accuracy, benefits and harms of screening and interventions in asymptomatic children five and under. Data Extraction: One investigator abstracted details about study design, patient population, setting, screening method, follow up, and results. Two investigators independently applied pre specified criteria to rate study quality using methods developed by the USPSTF. Discrepancies were resolved through consensus.
PROSPERO
N/A
DOI
10.26300/zpgg-es39
Notes
Data was entered retrospectively via the upload of the evidence and quality appendix tables in Word. The files uploaded for this project include: Appendix B1. Data Abstraction of Childhood Lead Screening Questionnaire Studies Appendix B2. Data Abstraction of Childhood Lead Capillary Screening Studies Appendix B3. Data Abstraction of Childhood Lead Treatment Trials Appendix C1. Quality Assessment of Childhood Lead Diagnostic Accuracy Studies Appendix C2. Quality Assessment of Childhood Lead Treatment Trials Appendix C3. Quality Assessment of Childhood Lead Treatment Cohort Study
Funding Source
This report is based on research conducted by the Pacific Northwest Evidence-based Practice Center (EPC) under contract to the Agency for Healthcare Research and Quality (AHRQ), Rockville, MD (Contract No. HHSA290201500009I, Task Order No. 7)

Key Questions

1. Key Question 1. Is there direct evidence that screening for elevated blood lead levels in asymptomatic children age 5 years and younger improves health outcomes (i.e., reduced cognitive or behavioral problems or learning disorders)?
2. Key Question 2a. What is the accuracy of questionnaires or clinical prediction tools that identify children who have elevated blood lead levels? 2b. What is the accuracy of capillary blood lead testing in children?
3. Key Question 3. What are the harms of screening for elevated blood lead levels (with or without screening questionnaires) in children?
4. Key Question 4. Do counseling and nutritional interventions, residential lead hazard control techniques, or chelation therapy reduce blood lead levels in asymptomatic children with elevated blood lead levels?
5. Key Question 5. Do counseling and nutritional interventions, residential lead hazard control techniques, or chelation therapy improve health outcomes in asymptomatic children with elevated blood lead levels?
6. Key Question 6. What are the harms of interventions in asymptomatic children with elevated blood lead levels?

Associated Extraction Forms

Associated Studies (each link opens a new tab)

TitleAuthorsYear
Prevalence of lead poisoning in an urban cohort of infants with high socioeconomic status.1994
The accuracy of a lead questionnaire in predicting elevated pediatric blood lead levels.1996
Blood lead levels in a continuity clinic population.1997
Evaluation of a childhood lead questionnaire in predicting elevated blood lead levels in a rural community.2003
Statewide assessment of lead poisoning and exposure risk among children receiving Medicaid services in Alaska.1997
Lead poisoning risk determination in a rural setting.1996
Development of a population-specific risk assessment to predict elevated blood lead levels in Santa Clara County, California.1995
The failure of CDC screening questionnaire to efficiently detect elevated lead levels in a rural population of children.1997
Rethinking the threshold for an abnormal capillary blood lead screening test.1996
Screening for pediatric lead poisoning. Comparability of simultaneously drawn capillary and venous blood samples.1994
A community outreach lead screening program using capillary blood collected on filter paper.1998
Evaluation and improvement of sample collection procedures for the determination of blood lead1993
Evaluation of home lead remediation in an Australian mining community.2009
A randomized, community-based trial of home visiting to reduce blood lead levels in children.2006
A randomized trial of calcium supplementation for childhood lead poisoning.2004
Children with moderately elevated lead levels: is chelation with DMSA helpful?1999
Effects of iron therapy on infant blood lead levels.2003
A community-based intervention for low-income families to reduce children’s blood lead levels between 3–9.9 μg/Dl2017
Effect of chelation therapy on the neuropsychological and behavioral development of lead-exposed children after school entry.2004
Do children with falling blood lead levels have improved cognition?2002
The effect of chelation therapy with succimer on neuropsychological development in children exposed to lead.2001
Safety and efficacy of succimer in toddlers with blood lead levels of 20-44 microg/dL. Treatment of Lead-Exposed Children (TLC) Trial Group.2000
Efficacy and toxicity of D-penicillamine in low-level lead poisoning.1988
Utility of a risk assessment questionnaire in identifying children with lead exposure.1996
Do questions about lead exposure predict elevated lead levels?1994

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