Recommendation Statement
The U.S. Preventive Services Task Force (USPSTF) is redesigning its recommendation
statement in response to feedback from primary care clinicians. The USPSTF
plans to release, early in 2007, a new, updated recommendation statement
that is easier to read and incorporates advances in USPSTF methods. The recommendation
statement below is an interim version that combines existing language and
elements with a new format. Although the definitions of grades remain the
same, other elements have been revised.
This recommendation statement was first published in Pediatrics.
Select for copyright and source information.
Summary of Recommendations Children Pregnant Women
Rationale Importance: Blood lead levels in children have declined dramatically in the United States over the past two decades. However, segments of the population remain at increased risk for higher blood lead levels. Even relatively low blood lead levels are associated with neurotoxic effects in children. Severely elevated blood lead levels in symptomatic pregnant women are associated with poor health outcomes; however, lead levels in this range are rare in the U.S. population.
Detection: There is good evidence that venous sampling accurately detects elevated blood lead levels and fair evidence that validated questionnaires are modestly useful in identifying children at increased risk for elevated blood lead levels.
Benefits of Detection and Early Intervention: The USPSTF found good quality evidence that interventions do not result in sustained decreases in blood lead levels 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 mild to moderately elevated blood lead levels. The USPSTF found no evidence examining the effectiveness of screening or interventions in improving health outcomes in asymptomatic pregnant women. Given the low prevalence of elevated blood lead levels 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 blood lead levels 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 blood lead levels, 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 blood lead levels 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 blood lead levels in children at average risk and in asymptomatic pregnant women outweigh the benefits. |
Contents
Summary
of Recommendations
Clinical Considerations
Discussion
References
Appendix
Disclaimer
Copyright
and Source Information
Clinical Considerations
- This USPSTF recommendation addresses screening for elevated blood lead
levels in children aged 1 to 5 years who are both at average and increased
risk, and in asymptomatic pregnant women.
- The highest mean blood lead levels in the U.S. occur in children aged 1-5
years (geometric mean 1.9 µg/dL). Children under 5 years of age are
at greater risk for elevated blood lead levels 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 blood lead levels 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 para-occupational exposures; and recent
immigration. Additional risk factors for pregnant women include alcohol use,
smoking, pica, and recent immigration status.
- Blood lead levels in childhood, after peaking at about 2 years of age,
decrease during short- and long-term followup without intervention. Most
lead is stored in bone. High bone lead levels can be present with normal
blood lead levels, so that blood lead levels often do not reflect the total
amount of lead in the body . This could explain the lack of effect of blood
lead level-lowering measures on reducing neurotoxic effects.
- Screening tests for elevated blood lead levels include free erythrocyte
(or zinc) protoporphyrin levels and capillary or venous blood lead levels.
Erythrocyte (or zinc) protoporphyrin is insensitive to modest elevations
in blood lead levels 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 blood lead level testing is preferred
to capillary sampling. Screening questionnaires may be of value in identifying
children at risk for elevated blood lead levels but should be tailored for
and validated in specific communities for clinical use.
- Treatment options in use for elevated blood lead levels 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 is offered for children with blood
lead levels from 10 to 20 µg /dL . Some experts have also recommended
nutritional counseling for children with blood lead levels in this range.
Residential lead hazard control is usually offered to children with blood
lead levels >20 µg/dL, while chelation therapy is offered to
children with blood lead levels >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 blood lead levels 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 blood
lead levels.
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Discussion
Burden of Illness
The prevalence of blood lead levels >10 µg/dL among children 1 to 5
years of age in the United States has declined from 9% between 1988 and 1991
to 1.6% between 1999 and 2002. The decline is due primarily to significant
reductions of lead in gasoline, air, dietary sources, and residential paint.
However, the prevalence varies substantially among different communities and
populations: mean blood lead levels of African-American children (2.8 µg/dL)
remain significantly higher than those of Mexican-American (1.9 µg/dL) and
non-Hispanic white children (1.8 µg/dL). Approximately 24 million housing
units still contain substantial lead hazards, with 1.2 million of these units
occupied by low-income families with young children. An estimated 310,000 children
remain at risk for exposure to harmful levels of lead. Population mean
blood lead levels in women of childbearing age and pregnant women have fallen
over the past two decades. In 1992, two large surveys of low-income pregnant
women found that between 0% and 6% of these women had blood lead levels >15 µg/dL. In
a recent sample of respondents to the of National Health and Nutrition Examination
Survey (NHANES) including 4394 women of child-bearing age, the geometric mean
blood lead level was 1.78 µg /dL.1,2
Elevated amounts of lead in the body affect various organ systems, including
the cardiovascular, renal, and hepatic, with most symptoms occurring with blood
lead levels > 50 µg /dL. Very high levels of inorganic lead exposure
may result in death or long-term neurologic sequelae in children.However, neurodevelopmental
dysfunction is associated with blood lead levels as low as 10 µg/dL in young
children. The adverse effects of very high maternal blood lead levels during
pregnancy include abortion, stillbirth, preterm delivery, decreased neonatal
head circumference, and decreased birth weight. Studies also suggest that mildly
elevated maternal blood lead levels may be associated with increased risk for
spontaneous abortion, hypertension in pregnancy, and adverse effects on fetal
growth.3 Although very high blood lead levels during pregnancy are harmful,
the adverse effects of antepartum lead levels on the fetus in the range typically
found in the U.S. have not been established.
Scope
The USPSTF examined new evidence published since it addressed
the following overarching question in its 1996 recommendation: does screening
children and pregnant women for elevated blood lead levels result in improved
neurodevelopmental outcomes? With this update, the USPSTF also reviewed the
evidence on the accuracy of screening tests, and the harms of screening and
treatment.
Accuracy of Tests
Blood tests or questionnaires may be used to screen for elevated blood lead
levels. Blood lead concentration is more sensitive and specific than free erythrocyte
protoporphyrin levels, but can be affected by environmental lead contamination
and laboratory analytic variation. Erythrocyte (or zinc) protoporphyrin is
insensitive to modest elevations in blood lead level and lacks specificity.
Capillary blood lead sampling has false-positive rates of 3% to 9% and false-negative
rates of 1% to 8%. The sensitivity and specificity of questionnaires vary considerably
with the prevalence of elevated blood lead levels in the population surveyed
and the cutoff blood lead level that is used. In urban and suburban populations,
Centers for Disease Control and Prevention (CDC) screening questionnaires detected
64% to 87% of children with blood lead levels of >10 µg/dL;
higher sensitivities (81%-100%) were reported for blood lead levels >15
to 20 µg/dL.
Specificity of these questionnaires ranged from 32% to 75%. False negative
results were low (0.2%-3.5%) in lower prevalence populations (2%-7%)
for levels of >10 µg/dL, but increased to 19% when the
population prevalence of elevated lead levels was higher (17-28%).4-6
Intervention- Treatment
Treatment options for elevated blood lead levels include residential lead
hazard-control efforts (ie, dust or paint removal, soil abatement, counseling,
and education), chelation, and nutritional interventions. Most studies of asymptomatic
children evaluate the effects of these interventions on blood lead levels instead
of on clinically relevant neurocognitive outcomes. The USPSTF found no studies
evaluating neurocognitive outcomes after residential lead hazard control efforts
or nutritional interventions. These interventions were found to have small,
inconsistent, or unsustained effects on blood lead levels in asymptomatic children
with mildly to moderately increased lead levels (<45 µg/dL).
There is good evidence that chelating agents benefit children with symptomatic
lead poisoning, but there is little evidence available to demonstrate a clinical
benefit from chelation therapy for children with lead levels <45 µg/dL.
A large, multicenter randomized controlled trial assessed the effect of oral
chelation therapy with succimer on IQ in children with venous blood lead concentrations
of 20 to 45 µg/dL.7 At 36 months' followup,
no statistically significant differences were found between treatment and control
groups in mean IQ, parental rating of behavior, or tests of learning ability. In
this trial, blood lead levels decreased in both the treatment and placebo groups,
and by 24 months the difference between treatment and placebo groups was not
statistically significant.8,9
The USPSTF found no studies that examined the effectiveness of interventions
in pregnant women.
Harms of Screening and Treatment
No new evidence was found regarding the harms of screening in children or
pregnant women. The most common harms of screening for elevated lead levels
are false-positive capillary results, anxiety, inconvenience, work or school
absenteeism, and financial costs associated with return visits and repeated
tests. In one randomized controlled trial, succimer was associated with a slight
decrease in cognitive performance.8,9
No studies have directly addressed the harms of interventions for pregnant women.
Research Needs
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. Evaluation of the effectiveness
of community-based interventions and recommendations regarding their use are
important areas of future research.
Recommendations of 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.10 This approach
is also supported by the American College of Preventive Medicine.11
The American Academy of Pediatrics (AAP) 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 AAP
recommends that pediatricians consider screening all children. Children should,
ideally, be tested at 1 and 2 years of age.12
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 blood lead level 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.13
Medicaid's Early and Periodic Screening, Diagnostic, and Treatment
Program requires that all children receive a screening blood lead test at 12
months and 24 months of age; children between the ages of 36 months and 72
months of age must receive a screening blood lead test if they have not been
previously screened for lead poisoning.
14,15
No national organizations currently recommend screening pregnant women for
elevated lead levels.
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References
1. Rischitelli
G, Nygren P, Bougatsos C, Freeman M, Helfand M. Screening for Elevated
Lead Levels in Childhood and Pregnancy: Update of the 1996 USPSTF Review.
Evidence Synthesis No. 44 (prepared by the Oregon Evidence-based Practice
Center under Contract No. 290-02-0024.) Rockville, MD: Agency for Healthcare
Research and Quality. December 2006. (Available on the AHRQ Web site
at: http://www.ahrq.gov/clinic/uspstf/uspslead.htm.)
2. Rischitelli
G, Nygren P, Bougatsos C, Freeman M, Helfand M. Screening for Elevated
Lead Levels in Childhood and Pregnancy: An Updated Summary of Evidence for
the US Preventive Services Task Force. Submitted Pediatrics.
3. Bellinger DC, Hu H, Kalaniti
K, et al. A pilot study of blood lead levels and neurobehavioral function in
children living in Chennai, India. Int J Occup Environ Health
2005;11(2):138-43.
4. Nordin JD, Rolnick SJ,
Griffin JM. Prevalence of excess lead absorption and associated risk factors
in children enrolled in a Midwestern health maintenance organization.
Pediatrics 1994;93(2):172-7.
5. Schaffer SJ, Szilagyi PG,
Weitzman M. Lead poisoning risk determination in an urban population through
the use of a standardized questionnaire. Pediatrics 1994;93(2):159-63.
6. Striph KB. Prevalence of
lead poisoning in a suburban practice. J Fam Pract 1995;41(1):65-71.
7. Rogan W. The Treatment
of Llead-exposed Children (TLC) trial: design and recruitment for a study of
the effect of oral chelation on growth and development in toddlers. Paediatr
Perinat Epidemiol 1998;12:313-33.
8. Rogan WJ, Dietrich KN,
Ware JH, et al. The effect of chelation therapy with succimer on neuropsychological
development in children exposed to lead. N Engl J Med 2001;344(19):1421-6.
9. Liu X, Dietrich KN, Radcliffe
J, Ragan NB, Rhoads GG, Rogan WJ. Do children with falling blood lead levels
have improved cognition? Pediatrics 2002;110(4):787-91.
10. Centers for Disease Control and Prevention. Screening Young Children for Lead Poisoning: Guidance for State and Local Health Officials. Atlanta, GA: USDHHS, 1997.
11. Lane WG, Kemper AR. American College
of Preventive Medicine Practice Policy Statement: Screening for Elevated Blood
Lead Levels in Children. Am J Prev Med 2001;20(1):78-82.
12. American Academy of Pediatrics Committee
on Environmental Health. Lead exposure in children: prevention, detection,
and management.. Pediatrics 2005;116:1036-46.
13. Ellis MR, Kane KY. Lightening the
lead load in children. Am Fam Physician 2000;62(3):545-54.
14. Centers for Disease Control and Prevention.
Blood Lead Levels - United States, 1999-2002. MMWR 2005;54(20):513-6.
15. Centers for Medicare and Medicaid
Services. Medicaid and EPSDT. http://www.cms.hhs.gov/MedicaidEarlyPeriodicScrn/.
Accessed December 15, 2006.
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Appendix
Corresponding Author: Ned Calonge, M.D., M.P.H., Chair, U.S. Preventive
Services Task Force, c/o Program Director, USPSTF, Agency for Healthcare Research
and Quality, 540 Gaither Road, Rockville, MD 20850, E-mail: uspstf@ahrq.gov.
Members of the U.S. Preventive Services Task Force
*: Ned Calonge, M.D., M.P.H., Chair, USPSTF (Chief
Medical Officer and State Epidemiologist, Colorado Department of Public Health
and Environment, Denver, CO); Diana B. Petitti, M.D., M.P.H. , Vice-chair, USPSTF
(Senior Scientific Advisor for Health Policy and Medicine, Regional Administration,
Kaiser Permanente Southern California, Pasadena, CA); Thomas G. DeWitt, M.D. (Carl
Weihl Professor of Pediatrics and Director of the Division of General and Community
Pediatrics, Department of Pediatrics, Children's Hospital Medical Center, Cincinnati,
OH); Leon Gordis, M.D., M.P.H., Dr.P.H. (Professor, Epidemiology Department, Johns Hopkins
Bloomberg School of Public Health, Baltimore, MD); Kimberly D. Gregory, M.D., M.P.H.
(Director, Women's Health Services Research and Maternal-Fetal Medicine, Department
of Obstetrics and Gynecology, Cedars-Sinai Medical Center, Los Angeles, CA); Russell
Harris, M.D., M.P.H. (Professor of Medicine, Sheps Center for Health Services Research,
University of North Carolina School of Medicine, Chapel Hill, NC); Kenneth W. Kizer,
M.D., M.P.H. (President and CEO, National Quality Forum, Washington, DC); Michael L.
LeFevre, M.D., M.S.P.H. (Professor, Department of Family and Community Medicine, University
of Missouri School of Medicine, Columbia, MO); Carol Loveland-Cherry, Ph.D., R.N. (Executive
Associate Dean, Office of Academic Affairs, University of Michigan School of Nursing,
Ann Arbor, MI); Lucy N. Marion, Ph.D., R.N. (Dean and Professor, School of Nursing, Medical
College of Georgia, Augusta, GA); Virginia A. Moyer, M.D., M.P.H. (Professor, Department
of Pediatrics, University of Texas Health Science Center, Houston, TX); Judith K.
Ockene, Ph.D. (Professor of Medicine and Chief of Division of Preventive and Behavioral
Medicine, University of Massachusetts Medical School, Worcester, MA); George F. Sawaya,
M.D. (Associate Professor, Department of Obstetrics, Gynecology, and Reproductive Sciences
and Department of Epidemiology and Biostatistics, University of California, San
Francisco, CA); Albert L. Siu, M.D., M.S.P.H. (Professor and Chairman, Brookdale Department
of Geriatrics and Adult Development, Mount Sinai Medical Center, New York, NY); Steven
M. Teutsch, M.D., M.P.H. (Executive Director, Outcomes Research and Management, Merck
& Company, Inc., West Point, PA); and Barbara P. Yawn, M.D., M.Sc. (Director of
Research, Olmstead Research Center, Rochester, MN).
*Members of the Task Force at the
time this recommendation was finalized. For a list of current Task Force members, go to http://www.ahrq.gov/clinic/uspstfab.htm.
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Disclaimer
Recommendations made by the USPSTF are independent of the U.S. Government.
They should not be construed as an official position of the Agency for Healthcare
Research and Quality or the U.S. Department of Health and Human Services.
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Copyright and Source Information
This document is in the public domain within the United States. For information
on reprinting, contact Randie Siegel, Director, Division of Printing and Electronic
Publishing, Agency for Healthcare Research and Quality, 540 Gaither Road, Rockville,
MD 20850.
Requests for linking or to incorporate content in electronic resources should
be sent to: info@ahrq.gov.
Source: Screening for elevated blood lead levels in children and pregnant women: Recommendation Statement. December 2006. Pediatrics 2006;118:2514-18.
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Current as of December 2006
Internet Citation:
U.S. Preventive Services Task Force. Screening for Elevated
Blood Lead Levels in Children and Pregnant Women: Recommendation Statement.
December 2006. Originally published in Pediatrics 2006;118:2514-18. Agency for Healthcare Research and Quality, Rockville, MD. http://www.ahrq.gov/clinic/uspstf06/lead/leadrs.htm