Physician's Handbook on Childhood Lead Poisoning Prevention
Chapter Four
Screening for Lead Poisoning
Summary
Children at risk for high-dose lead exposure should be screened with a blood lead test beginning at six months of age, or whenever the risk is first identified, as part of routine primary care, up to age six.
Children at risk for high-dose lead exposure whose blood lead levels are equal to or greater than 10 μg/dL should be retested every six months as long as the risk of high-dose exposure continues, or until they have had two subsequent consecutive blood lead results <10 μg/dL or three results <15 μg/dL at which time frequency of testing can be decreased to once a year until age six. All children, regardless of lead exposure risk, should be screened with a blood lead test at one- and two-years of age as part of routine primary care.
Providers who see children periodically for acute illness, but are not the primary care provider e.g., in hospitals, emergency rooms, community health centers or urgent care centers, should determine by history if these children have been screened with a blood lead test as part of routine primary care. Children six months to six years of age who are at risk for high-dose lead exposure and children one- and two-years of age who have not been screened previously should have a blood lead test or be referred for testing. For children ages three to six years who have never had a blood lead test, screening is recommended.
Child care providers: prior to or within three months of a child's initial enrollment, each child care provider, public and private nursery school and preschool, should request a copy of a certificate of lead screening for that child if the child is at least one-year of age. If the document cannot be obtained, the child care provider should refer the parent or guardian to the child's primary care provider and/or the local health department.
Screening for Lead Poisoning
Introduction
In the past, screening for lead poisoning was reserved for children who were recognized to be at high-risk due to factors such as living in an inner city or family history of lead poisoning. This strategy was effective when the goal was only to identify children with lead levels of 40 μg/dL or higher. With the recognition that lead levels > 10 μg/dL can be harmful, it has become clear that different screening strategies must be used to identify all children with elevated lead levels.
One change is the elimination of the use of erythrocyte protoporphyrin and related screening tests (EP, FEP). This test has been shown to be ineffective for identifying children with lead levels below 25 μg/dL. The only accurate measure known is a blood lead test. Therefore, only blood lead tests are to be used for lead screening.
Another change has been the introduction of universal screening at selected ages. The present strategy recommended by CDC and required by New York State Department of Health utilizes both high-risk screening when high-dose exposure risk is present, and universal screening of all children at ages one and two years.
Lead Screening as Part of Routine Health Supervision
As part of routine well child care, children six months to six years of age should be assessed for high-dose lead exposure at each well-child visit. This should be done by using a risk assessment questionnaire developed by the NYSDOH/AAP District II which is similar to the one proposed by CDC in 1991 (see Chapter 3 on Risk Assessment). Children found to be at risk for high-dose exposure should be screened with a blood lead test at the time the risk is identified.
Regardless of exposure risk, all children must be screened with a blood lead test at the one-year and two-year well child visits. For children ages three to six years who have never had a blood lead test, screening is recommended.
Venous blood is the preferred specimen for blood lead testing. Capillary blood may be used with appropriate collection procedures to minimize contamination of the specimen with lead from dust on the skin. The EP test is no longer acceptable for lead screening as significant numbers of children with elevated blood lead levels by current standards will have normal EP results.
Lead Screening by Providers of Episodic Care
Just as episodic providers are responsible for assessing the need for and providing immunizations, health care providers who see a child on an episodic basis are required to inquire whether the child has been assessed for lead exposure and screened as part of primary care. This includes providers in walk-in medical centers, emergency rooms, hospital inpatient services and other providers who may see a child on a one-time basis. If the child has not previously had the appropriate blood lead test, the provider must screen the child or refer the child for screening to the child's primary care provider or the local public health unit. This includes children six months to six years of age who are at risk for high-dose lead exposure and children one- to two-years of age who have not been screened previously, should have a blood lead test or be referred for testing. For a child three to six years of age who has never had a blood lead test, screening is recommended.
Screening for Lead Poisoning
Results of blood lead tests obtained by a provider of episodic care should be sent to the child's primary care provider. If there is no primary care provider, the results should be sent to the local health unit's Childhood Lead Poisoning Prevention Program for follow-up.
Lead Screening of Children Who Enroll in Child Care or Preschools
When a child enrolls in a day care center or preschool, the director should seek documentation from parents/guardians of lead screening of their child. If the child has never been screened previously, the parents/guardians should be informed of the importance of screening and be referred to their primary care provider or public health unit to obtain a blood lead test for their child. There is no requirement to exclude children from child care or preschool who have not been tested.
Pediatric care providers who screen children for lead poisoning must provide parents with documentation that the child has had a blood lead test. Parents/guardians can provide this information to the director of a day care center or preschool when they enroll their children. Pediatric care providers may use the certificate of lead screening which the State Department of Health has developed for this purpose, the New York State immunization card which has been modified to allow documentation of blood lead tests, the New York City or New York State parent-held health record or any of the health forms pediatric care providers are asked to complete for families enrolling in day care centers or preschools. If there is no primary care provider, the child care provider may refer the parent and child to the local public health unit.
Blood Collection for Lead Testing
Capillary specimens are easy to collect in the office setting, requires very little blood and are appropriate for initial screening. Contamination of the specimen with lead dust from the skin or air may cause falsely high levels to be reported. Scrupulous care is needed to minimize contamination of the capillary specimen. Elevated capillary blood lead results must be confirmed by repeating the test with a venous specimen. The Table below shows the recommended timetable for confirming various capillary blood lead levels.
Recommended Timetable for Confirming
Capillary Blood Lead
* Results with a Venous Blood Lead Measurement
| Capillary Blood Lead Level (ug/dL) |
Time Within Which Venous Blood Lead Confirmation Should Be Obtained |
|---|---|
| * Source: Modification of CDC, 1991, p 47 ** Children with blood lead levels <15 ug/dL are not required to have confirmatory testing. However, a follow-up venous sample is recommended within four months. |
|
| <10 | Not Necessary |
| 10-14 | Venous Sample Within Four Months** |
| 15-19 | Within One Month |
| 20-44 | Within One Week |
| 45-69 | Within 48 Hours |
| equal to or greater than 70 | Immediately |
Some laboratories will provide training for office staff in capillary blood collection technique. Collection methods and materials may be different for each lab. Obtain guidance from the laboratory before collecting or submitting capillary specimens.
Venous specimens are less likely to give false positive results due to contamination. Only venous blood should be used to confirm an elevated blood lead level obtained on an earlier capillary (or venous) specimen. It is always prudent to confirm an elevated blood lead level before embarking on an aggressive course of treatment.
Whether using capillary or venous blood, the collector must be certain that the materials used to hold or transport the blood do not contain lead which could contaminate the specimen. Glass or plastic vacuum collection tubes may contain lead. Always be certain that the manufacturer has certified that the tubes are lead-free before using them for blood lead collection.
Reporting of Blood Lead Results
Pediatric care providers submitting specimens to laboratories for blood lead testing must assure that needed information is supplied with the specimen, including: patient's name, date of birth, race, gender, address and county of residence of the child; type of sample (capillary or venous), date sample was collected and the name of the physician submitting the specimen. This information will be reported by the laboratory to the State's Childhood Lead Poisoning Registry.
When a child under six years is found to have a blood lead level of 45 μg/dL or greater, the health care provider must motify the local public health unit's childhood lead poisoning prevention program within 24 hours of learning that result. This will assure appropriateand timely public health involvement in management of the child, including environmental assessment.
(See appendix G for Local Program Contracts.)
The following screening and follow-up testing summary is based on the 1991 CDC Statement:
SCHEDULE FOR CHILDREN at low-risk FOR HIGH-DOSE LEAD EXPOSURE:
- A child without specific risk for high-dose lead exposure should have blood lead tests at 12 months and 24 months of age.
- If the blood lead test result is <10 μg/dL, the child's risk for high-dose lead exposure should continue to be assessed at each routine well-child visit or at least annually if the child has not had routine well-child visits.
- If a blood lead test result is 10-14 μg/dL, the child should be retested every three to four months. After two consecutive measurements are <10 μg/dL or three are <15 μg/dL, the child should be retested in a year.
- If any blood lead test result is equal to or greater than 15 μg/dL, the child should be retested every three to four months.
SCHEDULE FOR CHILDREN at high-risk FOR HIGH-DOSE LEAD EXPOSURE:
- A child at risk for high-dose lead exposure should have an initial blood lead test at six months of age or at any age when the exposure risk is identified.
- If the initial blood lead result is <10 μg/dL, the child should be retested every six months. After two subsequent consecutive measurements are <10 μg/dL or three are <15 μg/dL, testing frequency can be decreased to once a year.
- If a blood lead test result is 10-14 μg/dL, the child should be tested every three to four months. Once two subsequent consecutive measurements are <10 μg/dL or three are <15 μg/dL, testing frequency can be decreased to once a year.
- If any venous blood lead test result is >15 μg/dL, the child should be retested every three to four months and requires individual case management.
- Any child at high-risk by questionnaire should be screened at least once a year until his/her sixth birthday.
- Older children may need blood lead testing for specific indications. Examples include children with developmental delay and pica, hyperactive children and children with unexplained abdominal pain.
Laboratories for Blood Lead Testing
The New York State Department of Health certifies laboratories to perform blood lead tests. All laboratories licensed to perform blood lead testing by the State Department of Health participate in the state's proficiency testing program.
Every commercial lab in New York may offer blood lead testing by obtaining a specimen and sending it to another lab which has been certified to do the blood lead test. There may be a significant increase in price when a commercial lab sends out a specimen to another lab for testing.
Questionnaires were sent to all 65 laboratories certified to perform blood lead analysis in 1993. Among respondents to this survey, the most common analytical methods employed to determine lead concentration in a sample are atomic absorption spectrometry (AAS) with a graphite furnace (GFAAS) and an electrochemical technique known as anodic stripping voltammetry (ASV). These methods have an acceptable margin of error of 2-4 ug/dL. Most facilities repeat the analysis of samples with elevated blood lead levels for verification, although the trigger levels are not uniform.
Thirty-six surveyed laboratories perform lead testing on fingerstick samples with a price range of $8.50 to $60.00. Fifty-two surveyed laboratories perform lead testing on venous samples with a range of $3.60 to $63.85. The wide range of prices reflects differences among private and public laboratories, the availability of other tests and services in some facilities, as well as market forces. Forty-one laboratories provide phlebotomy services. Various laboratory services are available to providers.
Health care professionals who provide care to children may wish to identify facilities that meet their needs and the needs of their patients. If a child is identified as "at risk," consideration of turnaround time and urgent reporting of elevated results may be important. When performing venous confirmation on a child with a critical fingerstick blood lead level, a laboratory providing a "stat" test might be preferred. The availability of training in collection techniques, courier service or drawing stations may also influence choice, as well as the price.
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