The birth cohort children under 6 provides information about blood lead testing and blood lead levels (BLLs) among children born in the same year, known as a birth cohort. This indicator evaluates all BLL test results prior to a child’s sixth birthday. These data can be used to identify changes in blood lead levels over time and to monitor progress toward reducing and preventing exposure to lead in children.
Elevated BLLs in young children have been associated with adverse health effects ranging from learning impairment and behavioral problems to death. Since children may have elevated BLLs and not have any specific symptoms, Iowa requires all children to be tested at least once before the age of six.
The measures presented here focus on blood lead testing of children before their sixth birthday. Evaluating blood lead testing results in this way contributes to the overall understanding of the impact and burden of lead poisoning in Iowa. These measures can be helpful for healthcare providers and local public health agencies for program assessment and improvement, and to evaluate compliance with the testing requirement.
The children tested measures in the under 6 birth cohort evaluates all blood lead level (BLL) tests of children before their sixth birthday. Children are grouped based on the year they were born (the Birth Cohort Year). Evaluating blood lead levels in children under the age of six is important for program assessment and improvement, and to evaluate compliance with the testing requirement.
Measure Description
The Children Tested is the number of children born in the birth cohort year and tested for blood lead level (BLL) before age six.
The Children with Confirmed Elevated BLL is the number of children born in the birth cohort year and tested for blood lead level (BLL) before age six and had a confirmed result greater than or equal to 10 mcg/dL.
The Percent of Children with Confirmed Elevated BLL is the percent of children tested that had Confirmed Elevated BLL result.
Iowa requires all children to be tested at least once before the age of six. Measures based on these testing results can be helpful for healthcare providers and local public health agencies for program assessment and improvement, and to evaluate compliance with the testing requirement.
The number of children born from Vital Statistics data does not include children who have moved in or out of the area since birth. Therefore, as a denominator, vital statistics data may under or overestimate the number of 6-year-old children in the area. It is possible that there were more children tested in a County during the time period than were born in that County causing the Percent of Birth Cohort Tested to be greater than 100%.
Measure Description
The Children Tested is the number of children born in the Birth Cohort Year with at least one BLL test before their sixth birthday.
The Percent of Birth Cohort Tested is the percent Children Tested among the number of children born in the Birth Cohort Year.
The number and percent of children tested for blood lead prior to 6 years of age in Iowa, based on their birth year (cohort method).
Among children who were tested, the number and percent of children with elevated blood lead levels in the state of Iowa.
The geographic distribution of testing rates and elevated blood lead levels
To inform the public about testing coverage for blood lead levels in children and elevated blood lead levels.
For program planning and evaluation by state and local partners
Results are representative of children living in Iowa because blood lead testing is universal, all children are required to have at least 1 test before kindergarten. Statewide, over 95% of children are tested for blood lead by the time they reach 6 years of age, and only about 25% of children under 6 years of age are tested each year.
Data cannot tell us exactly how or where a child was exposed to lead.
Data on blood lead testing and elevated blood lead levels are provided by Iowa HHS which implements the Childhood Lead Poisoning Prevention Program (CLPPP), and are extracted from the Healthy Homes and Lead Poisoning Surveillance System (HHLPSS)
The Iowa Public Health Tracking portal displays lead testing data from the year 2000 through the most recent year of data available.
On October 28, 2021, CDC updated the blood lead reference value (BLRV) from 5.0 μg/dL to 3.5 μg/dL. A BLRV is intended to identify children with higher levels of lead in their blood compared with levels in most children. The value is based on the 97.5th percentile of the blood lead distribution in U.S. children ages 1–5 years.
The National Tracking Network defines a “confirmed” elevated blood lead level as one "venous" test result greater than or equal to 10 mcg/dL, or two "capillary" test results greater than or equal to 10 mcg/dL within 12 weeks of each other.
Capillary blood specimens are drawn from a finger stick, and the blood is collected either in capillary tubes or on filter paper. These specimens are considered "screening" tests because they are prone to falsely high results because of surface contamination when children's hands are not properly washed (prior to drawing the blood). Capillary tests, however, tend to be more acceptable to parents and may be performed in a wider range of settings (i.e., outside of clinical settings).
Venous specimens are considered "diagnostic" tests because they are drawn directly from a vein, but they may be less acceptable to some parents because of a child's discomfort. These tests also require greater expertise in drawing the blood.
If a child has multiple confirmed tests, only the highest confirmed test result is displayed. This applies to an individual test year or a birth year. However, children can appear in multiple test years using the annual method.
Blood lead testing is universal but not randomly sampled in Iowa, so the data collected by HHLPSS may not be representative of all Iowa children. Iowa HHS Childhood Blood Lead Screening Guidelines direct physicians to order blood lead tests for certain populations at higher risk for lead exposure.
The percent of children tested by birth year in a specific county can occasionally exceed 100%. This is because the percent of children tested is not calculated using the total number of children living in that county but, rather, is calculated using the total number of children born in a county in that birth year as a denominator. The number of children tested prior to 6 years of age in a specific county may be higher than the number of children that were born in that county.
Vital statistics data from Iowa HHS Vital Records maintains high quality information on all Iowa births, but errors may occur when using vital statistics data or total births as denominators for the birth cohort lead testing measure. A child's address on a birth certificate, for example, may be different from her/his address at the time of the lead test. Additionally, the number of children born in a specific geographic area does not include children who have moved in or out of that area since birth, so using total births as a denominator may lead to an inaccurate estimation of the number of children tested who are born in a specific year.
More detailed documentation of the lead poisoning data can be found in the following documents:
