Background

Excerpt from CDC's Morbidity and Mortality Weekly Report (MMWR) Supplements

September 12, 2014 / 63(02);36-42

Raymond, J. et.al 2014. Lead Screening and Prevalence of Blood Lead Levels in Children Aged 1-2 Years ? Child Blood Lead Surveillance System, United States, 2002-2010 and National Health and Nutrition Examination Survey, United States, 1999-2010.https://www.cdc.gov/mmwr/preview/mmwrhtml/su6302a6.htm

Introduction

Lead poisoning in children is preventable. However, in 2010, a total of 34 U.S. states and the District of Columbia (DC) identified approximately 24,000 children aged g/dL and approximately 243,000 children aged g/dL, the upper reference rangevalue*established in 2012 for follow-up blood lead testing in children aged 0-6 years (1). Permanent neurologic damage and behavior disorders have been associated with lead exposure even at detectable BLLs g/dL (2-5).

In 1991, CDC recommended that identification of children with BLLs ?10g/dL should prompt public health action by state or local health departments with follow-up testing (6). In 2012, CDC's Advisory Committee for Childhood Lead Poisoning Prevention (ACCLPP) recommended that CDC shift its priorities to primary prevention. ACCLPP provided additional guidance to clinicians related to the follow-up of children with BLLs of 5-10g/dL on the basis of evidence that these levels are associated with IQ deficits, attention-related behaviors, and poor academic achievement (7-10). ACCLPP also recommended using a reference range value based on the estimated 97.5 percentile of the BLL distribution among children aged 1-5 years calculated from two 4-year cycles of National Health and Nutrition Examination Survey (NHANES) data. In 2010, the upper value of the reference range was 5g/dL.

The Bright Futures guidelines, adopted by the American Academy of Pediatrics (AAP) in 1998 and endorsed by the Health Resources and Services Administration (HRSA) recommend that a clinical risk assessment for lead exposure be performed for infants (at ages 6 and 9 months), with blood lead testing to follow if positive. The assessment includes questions about Medicaid eligibility and living in housing built before 1978. The Bright Futures guidelines also recommend that children who are enrolled in Medicaid or living in high-risk areas as defined by the state or local health departments be screened for lead at ages 12 and 24 months (11). The National Committee for Quality Assurance has established a specific Healthcare Effectiveness Data and Information Set measure (i.e., the percentage of children who had one or more capillary or venous blood test for lead poisoning by their second birthday) (12). Because lead risk varies across the United States, the most recent CDC lead screening recommendations urge state and local health departments to assess local data on lead risks as the basis for developing lead screening recommendations for health-care providers that target children at risk in their areas, focusing on children aged 1-2 years (13).

Several risk factors are associated with lead exposure. The most common risk factor is living in a housing unit built before 1978, the year when residential use of lead paint was banned in the United States. If a child is identified as having a BLL ?5g/dL, ACCLPP recommends further assessment of the child and the home environment, follow-up treatment, and retesting the child's BLL until it has decreased to either g/dL or g/dL, depending on the state's guidelines (7). Follow-up treatment will vary depending on the child's BLL but might include health education, environmental investigations of the home or other places the child frequents, and chelation therapy (13). Data from state and local blood lead surveillance programs also can guide targeted primary prevention activities that control or eliminate lead sources before children are exposed and highlight geographic areas and special subpopulations (e.g., refugee populations) for which the risk for lead poisoning is greatest. AHealthy People 2020objective (objective EH-8.2) is to reduce the mean BLLs in children aged 14). The baseline level is 1.5g/dL, and the goal is 1.4g/dL. AnotherHealthy People 2020objective (objective EH-8.1) is to eliminate BLLs ?10g/dL in the same population (14).

The reports in this supplement provide the public and stakeholders responsible for infant, child, and adolescent health (including public health practitioners, parents or guardians and their employers, health plans, health professionals, schools, child care facilities, community groups, and voluntary associations) with easily understood and transparent information about the use of selected clinical preventive services that can improve the health of infants, children, and adolescents. The topic in this report is one of 11 topics selected on the basis of existing evidence-based clinical practice recommendations or guidelines for the preventive services and availability of data system(s) for monitoring (15). This report analyzes 2002-2010 data from CDC's Child Blood Lead Surveillance (CBLS) System to determine the proportion of U.S. children aged 1-2 years who were tested for lead. State and local health departments have their own definitions of the criteria for identifying children who are at risk, with a focus on children aged 1-2 years. However, because a single national definition of children at risk does not exist, establishing the screening rate of children at risk is not possible. This report also analyzes 1999-2010 data from NHANES to examine prevalence of BLLs ?5g/dL and ?10g/dL among children aged 1-2 years over time by factors that historically have predicted the risk for BLLs at or above the current reference value. Public health authorities and clinicians can use these data to identify population subgroups with suboptimal screening rates and target prevention tactics.

	NOTES ON SENSITIVITY AND SPECIFICITY
		Actual factor status
Test result	Present	Absent	Total
Positive	True positive (A)	False positive (B)	All positive tests (A+B)
Negative	False negative (C)	True negative (D)	All negative tests (C+D)
Total	All with factor	All without factor	Total (A+B+C+D)
	(A+C)	(B+D)

Sensitivity - the probability that the test result will be positive when administered to persons who actually have the factor.

sensitivity=