- Email: [email protected]
Should We Screen for Lead Poisoning After 36 Months of Age? Experience in the Inner City
Should We Screen for Lead Poisoning After 36 Months of Age? Experience in the Inner City Robert Karp, MD; Jill Abramson, MD, MPH; Margaret Clark-Golden, MD; Swati Mehta, MD; Rose Mary Daniele, MCS, FNP; Peter Homel, PhD; Jack Deutsch, PhD Introduction.—Current lead screening guidelines recommend monitoring lead levels in children under 3 years of age. There are, however, a number of children between the ages of 3 and 6 years who have elevated blood lead levels. Whether these lead elevations are new or chronic has not been examined. Objective.—To determine the proportion of children with lead levels greater than or equal to 10 mg/dL after their third birthday when all prior testing had been normal. Methods.—Retrospective study based on 39 000 venous lead tests obtained between 1993 and 1998. From this group, 2046 children were located who had blood lead levels of less than 10 mg/dL before 36 months and who had a followup lead level after 36 months. All lead assays were done by the City of New York laboratories, which had an intrasample variability of 13%. Results.—Sixty-six (3.2%) of the 2046 children showed an elevation in blood lead for the first time after their third birthday. The abnormal values ranged from 10 to 25 mg/dL. The majority (72%) of the screen-positive children, however, had lead levels of 10 to 12 mg/dL, and 63.3% of screen-positive children with repeat tests had lead levels that reverted to below 10 mg/dL. Conclusions.—The data indicate that some new cases of lead level elevations did occur after 3 years of age in this ‘high-risk’ community; however, the current study provides evidence that universal screening for lead poisoning beyond 3 years of age is not warranted in this community as it is not likely to pick up clinically important exposure. Ambulatory Pediatrics 2001;1:256 258
D
espite a dramatic reduction in blood lead levels over the past 20 years, a significant number of young children continue to have elevated blood lead levels. It is likely that some of these children will be left undiagnosed without a strategy for routine lead screening appropriate to their risk for lead poisoning.1–4 The finding of an elevated blood lead level in a preschoolaged child could either indicate a new exposure or a continuation of an ongoing unrecognized exposure to a source of lead. The present retrospective population-based study was undertaken to determine the proportion of inner-city children, known to be screen-negative prior to 36 months of age, who were found to have an elevated blood lead level after their third birthday. Data from the Third National Health and Nutrition Examination studies of 1988–91 showed that young children had the highest prevalence of elevated lead levels before 36 moths of age.5 These findings are supported by community surveys in Cincinnati,6 Philadelphia,7 and Galveston.8 Nevertheless, children studied by Melman et al7 in inner-city Philadelphia had their peak levels for blood lead at 37–48 months. Similarly, Javier et al8 found substantial numbers of children to have elevations in lead levels after
36 months of age. Neither study provided data showing whether the lead poisoning found after 3 years of age was of recent origin. Following the recommendations of the Centers for Disease Control,1 the Department of Health of the State of New York requires children to receive a blood lead test at 12 months and at 24 months of age, (or) between 36 and 72 months of age if they have not been previously screened.9 Historically, practitioners in New York and its Department of Health City have been vigilant, exceeding the state guideline by screening for lead poisoning beginning around 9 months of age and continuing thereafter until 6 years of age.10 Most pediatricians in the United States, however, are unlikely to continue screening after 36 months of age.11 METHODS Site Both Kings County Hospital Center (KCHC) and its principal satellite, the East New York Health Center (ENYHC), provide primary health care to a poor and underinsured population of children. The population served at these sites is predominantly of Afro-American or AfroCaribbean ancestry but includes recent immigrants from Africa, from the Middle and Far East, and from South and Central America. This low-income population largely resides in Victorian brownstone houses, pre–World War II apartment buildings, and in public housing built before 1950. The constellation of poor young children living in old lead-painted housing has given the ‘‘lead-belt’’ of Brooklyn one of the higher rates of childhood lead poi-
From the Lead Poisoning Prevention Programs, Kings County Hospital Center; and the Department of Health of the City of New York, The Children’s Medical Center, SUNY Downstate Medical Center, Brooklyn, New York. Address correspondence to Robert Karp, MD, Pediatrics—Box 49, SUNY–Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11202 (e-mail: [email protected]). Received for publication July 6, 1999; accepted May 4, 2001. AMBULATORY PEDIATRICS Copyright q 2001 by Ambulatory Pediatric Association
256
Volume 1, Number 5 September-October 2001
AMBULATORY PEDIATRICS
Lead Screening After 36 Months
Children With Lead Levels of 10 mg/dL and Above Lead level (mg/dL) Number of children
10
11
12
13
14
15
17
18
22
25
20
19
9
3
2
3
4
4
1
1
soning in the United States.9 Of note, a 1972 evaluation of children with hyperactivity who resided in these same neighborhoods showed a mean blood lead of level 22.7 6 9.6 mg/dL for control children—those without hyperactivity or known exposure to lead.12 Design Between 1993 and 1998, over 39 000 venous blood specimens were collected from patients at KCHC and ENYHC clinics. The samples were processed by the Laboratories of the Department of Health (DOH) of the City of New York, which follows standard procedure for assessing measurement error in each batch. The error rate was assessed for each run of collected samples. The blood lead levels [BLLs] along with the child’s name, date of birth, and date of test were imported to a dBase computer file and sorted using an SAS statistical package. The information accompanying the laboratory specimens allowed us to identify children who met the following inclusion criteria: the child was under 36 months of age at the time of the first lead screening; the pre–36month BLL was ,10 mg/dL, and the child had at least one more BLL after 36 months of age. RESULTS The 39 000 tests represented 12 524 children who were tested before 36 months of age. Three hundred twenty six children showed an elevation in lead level, leaving 12 198 children with lead screen results of less than 10 mg/dL. Of these 12 198 children without early lead poisoning, 2046 were tested beyond 36 months of age. Of the 2046 screened children, 66 (3.2%) showed an elevation in lead level of greater than 9 mg/dL for the first time after the third birthday (see the Table). Of the 66 screen-positive children, confirmatory tests were performed on 41. For 26 (63.3%) of the 41 children, the repeat test value was below 10 mg/dL. Intrasample variability established by the Laboratory of the New York City Department of Health was 13%. For this sample, 48 (72%) of screen positive children are within the range of random laboratory error. DISCUSSION Lead poisoning prevention programs have targeted children under the age of 36 months. This is the age group most clearly at risk; their normal activity of putting their hands and other objects in their mouths makes them most vulnerable to ingestion of environmental lead.1–6,9–11 In addition, the neurodevelopmental consequences of lead ingestion have been well documented in this age group, and greater developmental deficits have been shown to correlate with longer periods of exposure.1–3,6
257
The prevalence of new lead exposure among children over 3 years of age has not been studied. We found 66 of 2046 children who were screen negative before 3 years of age to have newly elevated lead levels after 3 years of age. The 66 children identified in the present study would have been missed if the current Centers for Disease Control and New York State guidelines had been followed. Of note, however, is that the majority of the lead screen– positive children had measurements for lead that were within the expected random error of the laboratory performing the measurement. Moreover, repeat testing of screen-positive children showed that 63.3% of screen-positive children with repeat tests had lead levels that reverted to values of below 10 mg/dL. The findings of the current study provide evidence that universal screening after 3 years of age for lead poisoning is not warranted in this particular high-risk community, as such screening is not likely to pick up clinically important exposure. The data indicate, however, that some children do ingest lead after the third birthday, such that their BLLs are elevated. Thus, it would seem prudent to screen all inner-city low-income children using a risk questionnaire when the child is between 36 and 72 months of age, reserving blood lead level measurements for children with specific indicators.2,3 These indicators include low income, exposure in the home, no lead test on record, recent remodeling within the child’s home, or behavioral characteristics associated with lead poisoning.13–15 Other highrisk communities might have a different outcome on evaluation of their data. Similar evaluation is suggested before abandoning the recommendation to perform universal screening among preschool children. Fortunately, the prevalent finding of low but toxic blood lead levels among Brooklyn children in the 1970s12 was not replicated in the 1990s. The improvement is noted; we express appreciation for the efforts of the pediatric and public health communities as well as those of concerned citizens. The constancy of poverty in the inner city reminds us of the need to be continually vigilant for the danger of lead rather than to be complacent about our successes.13–15 REFERENCES 1. Centers for Disease Control and Prevention. Preventing Lead Poisoning in Young Children: Guidance for State and Local Public Health Officials. Atlanta, Ga: US Dept of Health and Human Services; 1997. 2. American Academy of Pediatrics Committee on Environmental Health. Screening for elevated blood lead levels. Pediatrics. 1998;101:1072–1077. 3. Harvey B. New lead screening guidelines from the Centers for Disease Control and Prevention. How will they affect pediatricians. Pediatrics. 1997;100:384–388. 4. Report of the Ranking Minority Member, Committee on Government Reform. Lead Poisoning: Federal Health Care Programs Are Not Effectively Reaching At-Risk Children. United States General Accounting Office, 1999. Document GAO/ HEHS-99-18. 5. Morbidity and Mortality Weekly Report. Current trend, blood lead levels—United States, 1988–1991. Morbid Mortal Wkly Rep. 1994;43:545–548. 6. Dietrich KM, Berger OG, Succop PA. Lead exposure and the
258
7.
8.
9.
10.
Karp et al motor developmental status of urban six-year-old children in the Cincinnati Prospective Study. Pediatrics. 1993;91:301–307. Melman ST, Nimeh JW, Anbar RD. Prevalence of elevated blood lead levels in an inner-city pediatric population. Environ Health Perspect. 1998;106:655–657. Javier FC III, McCormick DP, Alcock NW. Lead screening among low-income children in Galveston, Texas. Clin Pediatr. 1999;38:655–660. Lofgren JP, Macias M, Russakow S, et al. Blood lead levels in young children: United States and selected states, 1996–1999. Morb Mortal Wkly Rep. 2000;49:1133–1137. New York City Department of Health. Childhood Lead Poisoning. Albany, NY: New York City Dept of Health, City Health Information; 1998.
AMBULATORY PEDIATRICS 11. Campbell JR, Shaffer SJ, Szilagyi PG, et al. Blood lead screening practices among US pediatricians. Pediatrics. 1996;98:372– 377. 12. David OJ, Clark J, Voeller K. Lead and hyperactivity. Lancet. 1972;2:900–903. 13. Harris P, Clark M, Karp RJ. The prevention of lead poisoning. In: Karp RJ, ed. Malnourished Children in the United States: Caught in the Cycle of Poverty. New York: Springer Publishing Co; 1993:91–100. 14. Needleman H. Childhood lead poisoning: the promise and abandonment of primary prevention. Am J Public Health. 1998;88: 1871–1877. 15. Silbergeld AK. Preventing lead poisoning in children. Ann Rev Public Health. 1997;18:187–210.
D
espite a dramatic reduction in blood lead levels over the past 20 years, a significant number of young children continue to have elevated blood lead levels. It is likely that some of these children will be left undiagnosed without a strategy for routine lead screening appropriate to their risk for lead poisoning.1–4 The finding of an elevated blood lead level in a preschoolaged child could either indicate a new exposure or a continuation of an ongoing unrecognized exposure to a source of lead. The present retrospective population-based study was undertaken to determine the proportion of inner-city children, known to be screen-negative prior to 36 months of age, who were found to have an elevated blood lead level after their third birthday. Data from the Third National Health and Nutrition Examination studies of 1988–91 showed that young children had the highest prevalence of elevated lead levels before 36 moths of age.5 These findings are supported by community surveys in Cincinnati,6 Philadelphia,7 and Galveston.8 Nevertheless, children studied by Melman et al7 in inner-city Philadelphia had their peak levels for blood lead at 37–48 months. Similarly, Javier et al8 found substantial numbers of children to have elevations in lead levels after
36 months of age. Neither study provided data showing whether the lead poisoning found after 3 years of age was of recent origin. Following the recommendations of the Centers for Disease Control,1 the Department of Health of the State of New York requires children to receive a blood lead test at 12 months and at 24 months of age, (or) between 36 and 72 months of age if they have not been previously screened.9 Historically, practitioners in New York and its Department of Health City have been vigilant, exceeding the state guideline by screening for lead poisoning beginning around 9 months of age and continuing thereafter until 6 years of age.10 Most pediatricians in the United States, however, are unlikely to continue screening after 36 months of age.11 METHODS Site Both Kings County Hospital Center (KCHC) and its principal satellite, the East New York Health Center (ENYHC), provide primary health care to a poor and underinsured population of children. The population served at these sites is predominantly of Afro-American or AfroCaribbean ancestry but includes recent immigrants from Africa, from the Middle and Far East, and from South and Central America. This low-income population largely resides in Victorian brownstone houses, pre–World War II apartment buildings, and in public housing built before 1950. The constellation of poor young children living in old lead-painted housing has given the ‘‘lead-belt’’ of Brooklyn one of the higher rates of childhood lead poi-
From the Lead Poisoning Prevention Programs, Kings County Hospital Center; and the Department of Health of the City of New York, The Children’s Medical Center, SUNY Downstate Medical Center, Brooklyn, New York. Address correspondence to Robert Karp, MD, Pediatrics—Box 49, SUNY–Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11202 (e-mail: [email protected]). Received for publication July 6, 1999; accepted May 4, 2001. AMBULATORY PEDIATRICS Copyright q 2001 by Ambulatory Pediatric Association
256
Volume 1, Number 5 September-October 2001
AMBULATORY PEDIATRICS
Lead Screening After 36 Months
Children With Lead Levels of 10 mg/dL and Above Lead level (mg/dL) Number of children
10
11
12
13
14
15
17
18
22
25
20
19
9
3
2
3
4
4
1
1
soning in the United States.9 Of note, a 1972 evaluation of children with hyperactivity who resided in these same neighborhoods showed a mean blood lead of level 22.7 6 9.6 mg/dL for control children—those without hyperactivity or known exposure to lead.12 Design Between 1993 and 1998, over 39 000 venous blood specimens were collected from patients at KCHC and ENYHC clinics. The samples were processed by the Laboratories of the Department of Health (DOH) of the City of New York, which follows standard procedure for assessing measurement error in each batch. The error rate was assessed for each run of collected samples. The blood lead levels [BLLs] along with the child’s name, date of birth, and date of test were imported to a dBase computer file and sorted using an SAS statistical package. The information accompanying the laboratory specimens allowed us to identify children who met the following inclusion criteria: the child was under 36 months of age at the time of the first lead screening; the pre–36month BLL was ,10 mg/dL, and the child had at least one more BLL after 36 months of age. RESULTS The 39 000 tests represented 12 524 children who were tested before 36 months of age. Three hundred twenty six children showed an elevation in lead level, leaving 12 198 children with lead screen results of less than 10 mg/dL. Of these 12 198 children without early lead poisoning, 2046 were tested beyond 36 months of age. Of the 2046 screened children, 66 (3.2%) showed an elevation in lead level of greater than 9 mg/dL for the first time after the third birthday (see the Table). Of the 66 screen-positive children, confirmatory tests were performed on 41. For 26 (63.3%) of the 41 children, the repeat test value was below 10 mg/dL. Intrasample variability established by the Laboratory of the New York City Department of Health was 13%. For this sample, 48 (72%) of screen positive children are within the range of random laboratory error. DISCUSSION Lead poisoning prevention programs have targeted children under the age of 36 months. This is the age group most clearly at risk; their normal activity of putting their hands and other objects in their mouths makes them most vulnerable to ingestion of environmental lead.1–6,9–11 In addition, the neurodevelopmental consequences of lead ingestion have been well documented in this age group, and greater developmental deficits have been shown to correlate with longer periods of exposure.1–3,6
257
The prevalence of new lead exposure among children over 3 years of age has not been studied. We found 66 of 2046 children who were screen negative before 3 years of age to have newly elevated lead levels after 3 years of age. The 66 children identified in the present study would have been missed if the current Centers for Disease Control and New York State guidelines had been followed. Of note, however, is that the majority of the lead screen– positive children had measurements for lead that were within the expected random error of the laboratory performing the measurement. Moreover, repeat testing of screen-positive children showed that 63.3% of screen-positive children with repeat tests had lead levels that reverted to values of below 10 mg/dL. The findings of the current study provide evidence that universal screening after 3 years of age for lead poisoning is not warranted in this particular high-risk community, as such screening is not likely to pick up clinically important exposure. The data indicate, however, that some children do ingest lead after the third birthday, such that their BLLs are elevated. Thus, it would seem prudent to screen all inner-city low-income children using a risk questionnaire when the child is between 36 and 72 months of age, reserving blood lead level measurements for children with specific indicators.2,3 These indicators include low income, exposure in the home, no lead test on record, recent remodeling within the child’s home, or behavioral characteristics associated with lead poisoning.13–15 Other highrisk communities might have a different outcome on evaluation of their data. Similar evaluation is suggested before abandoning the recommendation to perform universal screening among preschool children. Fortunately, the prevalent finding of low but toxic blood lead levels among Brooklyn children in the 1970s12 was not replicated in the 1990s. The improvement is noted; we express appreciation for the efforts of the pediatric and public health communities as well as those of concerned citizens. The constancy of poverty in the inner city reminds us of the need to be continually vigilant for the danger of lead rather than to be complacent about our successes.13–15 REFERENCES 1. Centers for Disease Control and Prevention. Preventing Lead Poisoning in Young Children: Guidance for State and Local Public Health Officials. Atlanta, Ga: US Dept of Health and Human Services; 1997. 2. American Academy of Pediatrics Committee on Environmental Health. Screening for elevated blood lead levels. Pediatrics. 1998;101:1072–1077. 3. Harvey B. New lead screening guidelines from the Centers for Disease Control and Prevention. How will they affect pediatricians. Pediatrics. 1997;100:384–388. 4. Report of the Ranking Minority Member, Committee on Government Reform. Lead Poisoning: Federal Health Care Programs Are Not Effectively Reaching At-Risk Children. United States General Accounting Office, 1999. Document GAO/ HEHS-99-18. 5. Morbidity and Mortality Weekly Report. Current trend, blood lead levels—United States, 1988–1991. Morbid Mortal Wkly Rep. 1994;43:545–548. 6. Dietrich KM, Berger OG, Succop PA. Lead exposure and the
258
7.
8.
9.
10.
Karp et al motor developmental status of urban six-year-old children in the Cincinnati Prospective Study. Pediatrics. 1993;91:301–307. Melman ST, Nimeh JW, Anbar RD. Prevalence of elevated blood lead levels in an inner-city pediatric population. Environ Health Perspect. 1998;106:655–657. Javier FC III, McCormick DP, Alcock NW. Lead screening among low-income children in Galveston, Texas. Clin Pediatr. 1999;38:655–660. Lofgren JP, Macias M, Russakow S, et al. Blood lead levels in young children: United States and selected states, 1996–1999. Morb Mortal Wkly Rep. 2000;49:1133–1137. New York City Department of Health. Childhood Lead Poisoning. Albany, NY: New York City Dept of Health, City Health Information; 1998.
AMBULATORY PEDIATRICS 11. Campbell JR, Shaffer SJ, Szilagyi PG, et al. Blood lead screening practices among US pediatricians. Pediatrics. 1996;98:372– 377. 12. David OJ, Clark J, Voeller K. Lead and hyperactivity. Lancet. 1972;2:900–903. 13. Harris P, Clark M, Karp RJ. The prevention of lead poisoning. In: Karp RJ, ed. Malnourished Children in the United States: Caught in the Cycle of Poverty. New York: Springer Publishing Co; 1993:91–100. 14. Needleman H. Childhood lead poisoning: the promise and abandonment of primary prevention. Am J Public Health. 1998;88: 1871–1877. 15. Silbergeld AK. Preventing lead poisoning in children. Ann Rev Public Health. 1997;18:187–210.