Standard Surveillance Definitions and Classifications

Notice: CDC has recently updated its recommendations on children’s blood lead levels (BLLs).

• In 2012, CDC defined a reference level of 5 micrograms per deciliter (µg/dL) to identify children with elevated blood lead levels. These children are exposed to more lead than most children.
• This reference value is based on the 97.5th percentile of the National Health and Nutrition Examination Survey’s (NHANES) blood lead distribution in children. The current reference value is based on NHANES data from 2007-2008 and 2009-2010. CDC will update the reference value every four years using the two most recent NHANES surveys.
• Once new NHANES data are released, CDC will analyze the last two sets of NHANES data to find the 97.5th percentile of blood lead distribution in children. Once we know that number we can determine whether to change the reference value.
• Until 2012, children were identified as having a blood lead “level of concern” if the test result was 10 or more µg/dL of lead in blood. CDC is no longer using the term “level of concern” and is instead using the reference range value to identify children with elevated blood lead levels.
• For more information, please visit https://www.cdc.gov/nceh/lead/ACCLPP/blood_lead_levels.htm.

CDC uses the following surveillance definitions for all states:

• Test: Any blood lead draw (capillary, venous or unknown sample type) on a child that produces a quantifiable result and is analyzed by a Clinical Laboratory Improvement Amendments (CLIA)-certified facility or an approved portable device. A blood lead test may be collected for screening, confirmation, or follow-up.
• Screening test: A blood lead test for a child age <72 months who previously did not have a confirmed elevated BLL. (NOTE: A child may be screened in multiple years or even multiple times within a given year, but would be counted only once for each year.)
• Elevated BLL: A single blood lead test (capillary or venous) at or above the reference range value of 5 µg/dL established in 2012.
• Confirmed elevated BLL ≥ 10 μg/dL: A child with one venous blood specimen ≥ 10 μg/dL, or two capillary blood specimens ≥ 10 μg/dL drawn within 12 weeks of each other.
• Unconfirmed elevated BLL ≥ 10 μg/dL: A single capillary blood lead test ≥ 10 μg/dL, or two capillary tests ≥ 10 μg/dL drawn more than 12 weeks apart.
• Percent of children with elevated BLLs: The number of children less than 72 months of age with an elevated blood lead level ≥5 µg/dL divided by the number of children less than 72 months of age tested for blood lead, multiplied by 100. Also referenced as “Case Rate.”
• 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 based on 2000 (years) or 2010 (years) U.S. Census data, multiplied by 100.

Classifications

Once a child has had one confirmed elevated BLL, if in subsequent years he or she has another elevated test result, regardless of the test type, we include that child in the tables showing the number of children with confirmed elevated BLLs for each year he or she continues to have an elevated BLL test result (prevalence data).

However, a child is counted only once for each year in which he or she is tested and has an elevated BLL. In a subsequent year, if a child with a confirmed elevated BLL has no follow-up test or only follow-up tests that are below 5 μg/dL, the child would not be counted with confirmed elevated BLLs for that year.