Standard Surveillance Definitions and Classifications
CDC applies the following nationally consistent standard definitions and classifications for blood lead surveillance data from all states. A child may be screened in multiple years or even multiple times within a given year. However, in CDC data tables, a child is only counted once per each year based on their highest blood lead level.
These definitions are to be used for classifying blood lead surveillance data. However, decisions about the timing and sampling method for use in confirmatory and follow up testing should be made based on CDC’s Recommended Actions Based on Blood Lead Level.
- Test: Any blood lead draw (capillary, venous or unknown sample type) on a child <16 years of age that produces a quantifiable result and is analyzed by a Clinical Laboratory Improvement Amendments (CLIA)-certified facility or an approved (CLIA waived) portable device.
- Test type: A blood lead test may be collected for screening, confirmation, or follow-up.
- Sample type: A blood lead test may be collected as a venous, capillary, or unknown blood specimen type.
- Screening test: A blood lead test for a child age <72 months who previously did not have a confirmed elevated BLL.
- Confirmed BLL ≥ CDC’s blood lead reference value: A child with one venous blood test ≥ 3.5 μg/dL or two capillary blood tests ≥ 3.5 μg/dL drawn within 12 weeks of each other.
- Unconfirmed BLL ≥ CDC’s blood lead reference value: A single capillary blood lead test ≥ 3.5 μg/dL or two capillary tests ≥ 3.5 μg/dL drawn more than 12 weeks apart.
- Percent of children with BLLs ≥ CDC’s blood lead reference value: The number of children less than 72 months of age with a blood lead level ≥ 3.5 µg/dL divided by the number of children less than 72 months of age tested for blood lead, multiplied by 100.
- Percent of children tested: The number of children less than 72 months of age tested for blood lead divided by the total number of children less than 72 months of age within a geographic unit (i.e., county or state) based on annual intercensal estimates for the most recent U.S. Census data, multiplied by 100. (Also referred to as “screening penetrance”).