Section I: Testing and Results
Blood Lead Test Reporting
Since 1994, NYS has required reporting of all blood lead tests regardless of blood lead level. Only authorized laboratories in accordance with Public Health Law Article 5, Title V can accept and analyze blood lead specimens. The State Health Department's Wadsworth Center for Labs and Research (WCL&R) conducts a comprehensive program of clinical and environmental laboratory evaluation and accreditation. WCL&R ensure that quality laboratory services are maintained through regular inspections, proficiency testing, and availability of technical assistance, including remedial training.
The State Health Department transmits all electronically submitted laboratory results to local health departments for the children in their jurisdiction on a daily basis. Those laboratories that do not report electronically send manually submitted reports simultaneously to the local health department programs and to the State Health Department. Local health departments then match laboratory test results to children identified in their local database.
Each local health department periodically transmits records of its local childhood lead data to the State Health Department's Childhood Lead Poisoning Prevention Program. Local data are then loaded into a master database used for epidemiological purposes.
Note: A number of terms associated with blood lead testing are defined in the Appendix.
Since the July 2000 report was released, significant enhancements were made in the methodology used to evaluate data. These changes do not allow for direct comparisons of the data from this report (2000-2001) to the 2000 report (1999 and earlier).
The reader should be aware of two potential data limitations in the interpretation of screening rates and new cases of EBL:
Because of family migration from one county to another, it is possible for multiple counties to report screening results to the state for the same child. Therefore, the state data are not an unduplicated count of all children screened, and the statewide screening rate calculation could be inflated.
Small sample size
Caution must be used in interpreting incidence or new case rates from counties or zip codes with low screening rates. In these instances, even a small number of children with elevated blood lead levels can result in a high incidence (new case) rate that may not accurately reflect the entire county or zip code. The more children screened, and the higher the screening rate, the more likely that the incidence rate is a true reflection of the rate of elevated blood lead in the total population.
Blood Lead Test Process
Children may receive a blood lead test either to screen for elevated blood lead or as a follow-up test due to a previously elevated screening test. Two types of sampling methods are used: venous or capillary blood draw. Venous blood is the preferred specimen for blood lead testing. Capillary specimens are subject to lead contamination if special collection techniques are not observed. Therefore, tests performed on a capillary specimen may be falsely reported as elevated when in fact the child does not have an elevated blood lead level. To assure that children are not falsely identified, a confirmatory test with a venous sample is recommended when a capillary test shows elevated blood lead (EBL).
In 2001, 68% of all children screened received a venous blood lead draw as their initial test. This represents an increase of approximately 7% over those children who received an initial venous blood lead test in 2000. The use of venous blood sampling varied; however, 44 NYS counties (77%) reported venous sampling as the predominant type of initial screening test. Venous blood sampling ranged from a low of 13% to a high of 98% among all counties outside of NYC (data not shown). Health care providers increasingly recognize the benefit of drawing a single venous specimen as it serves the dual purpose of being both a screening and a confirmatory test.
Screening for Blood Lead Levels
The purpose of testing, or screening for blood lead levels, is to provide for the early identification of children with elevated blood lead levels and, once identified, coordinate intervention services. NYS regulations require health care providers to test all children for blood lead levels at age one and again at age two for monitoring and early detection during a period of a child's greatest risk.
Percentage of Children Screened Statewide
The percentage of children screened for EBL was examined for the following age groups: 0 to 15 months, 16 to 23 months, 24 to 35 months, and 36 to <72 months. Table 1 shows that slightly more than half (51.5%) of children received an initial blood lead screening test before 16 months of age.
The number and percentage of children receiving their first screening test for blood lead levels by age one (or less than 24 months) by birth year cohort is illustrated in Figure 1. The percentage of children who receive at least one screening test by age 24 months has increased slightly over time. Sixty five percent of children born in 1999 received their first screening test by age 24 months compared to 59% of children born in 1994. This represents a 6 percent increase. The overall percentage of children born in New York State between 1994 and 1996 receiving a blood lead screening test before age six (72 months) has remained at a consistently high rate of approximately 90% (Table 1).
State and County Comparisons
Figures 2 and 3 illustrate how counties compare to the median statewide screening rate for children initially screened by age one (<24 months) for birth cohorts 1998 and 1999. Screening rates by county are ordered from high to low as follows: Counties with screening rates above the state's 75th percentile are identified as having "high" screening rates. Counties identified with screening rates between the 25th and 75th percentile are categorized as having "moderate" screening rates. Finally, counties with screening rates below the state's 25th percentile are classified as having "low" screening rates.
Counties with particularly high screening rates are scattered throughout the state and include Cayuga, Clinton, Cortland, Erie, Essex, Fulton, Jefferson, Monroe, Onondaga, Oswego, Otsego, Tompkins, and Westchester.
Identification of Children with Elevated Blood Lead Levels
Prevalence: Children with EBL, New and Ongoing Cases
Prevalence data indicate the proportion of children with confirmed EBL among those children who continue to have their blood lead level monitored. This measure reflects both current (newly identified) and past (identified previously, but ongoing) cases of children with EBL in the population. Nationally, prevalence is the most commonly used measure of blood lead elevations. The measure is sometimes contrasted to measures of incidence, which assesses only the occurrence of new cases. Prevalence rates are higher than incidence rates as prevalence rates include all children with elevated levels, including those identified in prior years that still receive follow-up tests.
New York's prevalence rate declined over the two-year period examined. Between years 2000 and 2001, the prevalence of children with EBL of 20ug/dL or greater decreased by 21%, and the prevalence of children with EBL of 10-19ug/dL decreased by 17%. The proportion of children in 2001 with levels of 10 ug/dL or greater was 2.7 per 100 children tested, and the proportion of children with levels of 20 ug/dL or greater was less than 1.0 per 100 (Table 2).
Incidence: Children Newly Identified With EBL
The number and rates of children under six years of age newly identified as a case in years 2000 and 2001 are provided in Table 3. Fewer new cases were identified in 2001 as compared to 2000. The incidence of confirmed EBL cases of 20ug/dL or higher decreased from 551 in 2000 to 415 in 2001, a decrease of 25%. The incidence of children identified with an elevated blood level between 10 and 19 ug/dL decreased by 11.5% from 3,121 in 2000 to 2,763 in 2001.
The incidence rate, or rate of newly identified cases of 10-19ug/dL or greater declined from 1.7 per 100 children screened in 2000 to 1.5 in 2001. Rates among children with confirmed EBL of 20ug/dL or greater declined from 3 children being identified per 1,000 screened in year 2000 to 2 children per 1,000 screened in year 2001.
Figure 4 illustrates how individual counties compare to the statewide incidence rate of children newly identified with confirmed EBL of 10 ug/dL or greater, using an average of the rates over the three year period 1999-2001. Counties were once again categorized as high, moderate, or low rates, as described earlier.
Children Screened a Second Time for Lead Exposure
Children may be exposed to lead at any time, including after the time at which they were initially screened. Therefore, while an initial screen at the appropriate age is important, a second screening is also important. In general, children more actively explore their environment as their mobility increases between the ages of one and two. In addition, some children may have changed residences or regularly spent time at a different address that has lead hazards.
Children born between 1994 and 1999 and whose initial screening test (by 12/31/1999) showed no elevated lead levels (<10ug/dL) were evaluated to determine if a second screening test was done.
A total of 992,902 children initially screened and found to have a non-elevated blood lead level were eligible to be screened a second time. Just over one-third, or 320,083 of these children received a second screening test by 12/31/2001 as illustrated in Figure 5. Of those, 25,286 (8%) were found during the second test to have an elevated blood lead level of 10 ug/dL or higher (including confirmed and unconfirmed test results). This finding demonstrates the importance of a second screening test even if an initial screening test is negative.
County Level Comparisons
County level comparisons of second screening test rates and resulting new cases are shown in Table 4. Fourteen counties (or 25%) indicated that at least 30% of the eligible children were screened a second time for elevated blood lead levels.
Mapping of New Cases (Incidence) by Zip Codes
Analysis of aggregate data in large geographic areas can mask smaller populations with relatively high rates of elevated blood lead levels. To more easily identify geographic areas with high rates of children with elevated blood lead levels, an analysis of zip code level data was conducted for all zip codes outside of New York City. Zip codes are used because they are more universally understood than other measures, such as census tracts.
Most children in the database had only one street address associated with their record. However, some children had multiple addresses, with no information concerning which address was the likely source of lead poisoning. In these cases, the zip code associated with a child's initial screening test was used. Zip codes were validated against the street name and city, and if necessary the zip code was corrected.
Zip Codes With High Incidence Rates
Zip codes are ordered from highest to lowest by the percentage of newly confirmed cases above 10 ug/dL. To provide greater stability and reliability, only zip codes with at least 100 children screened each year from 1999-2001 are used. Zip codes with more than three times the statewide incidence rate for 2001 (1.7%) and which were among the 100 zip codes with the highest incidence rates for years 1999 and 2000 were defined as high-incidence (Table 5 and Figure 6).
In 2000-2001, thirty-six (36) of the state's approximately 1,700 non-New York City zip codes were identified as having at least 5 new cases per 100 children screened (or >5% incidence rate). These 36 zip codes, which comprise 2% of the state's zip codes outside of NYC, accounted for 41% (1,505 in 2000 and 1,287 in 2001) of all the children who were identified with EBL outside of NYC. Among counties with one or more high-incidence zip codes, the high-incidence zip codes accounted for almost half of these counties' overall incidence rate.
Housing and Demographic Characteristics of High Incidence Zip Codes
Table 6 shows housing data from Census 2000. As expected, the thirty-six zip codes with high incidence rates had a higher proportion of pre-1950 housing stock (59%) than the statewide (37%) and county figures.
Census 2000 provides data on families living in poverty who have a child under the age of 5 years. A family is defined as living in poverty if their income is below the federal poverty level as defined by the US Department of Health and Human Services for that family's size and composition ($18,400 for a family of four in 2003). As shown in Table 7, a higher percentage of families in the 36 zip codes include children under age five living in poverty when compared to statewide and county levels. For example, in Albany County, 16.8% of all families with children under the age of 5 live in poverty, but 36.1% of families with children under the age of 5 in the five high-incidence zip codes live in poverty.
NYS Counties are depicted in Figure 7 as having a high percentage (75th percentile or higher), moderate percentage (inter quartile range), or low percentage (25th percentile or lower) of pre-1950 constructed housing units.