Lead in Blood
2023 Case Definition

Background

Lead adversely affects multiple organ systems and can cause permanent damage, including neurotoxicity and adverse cardiovascular, renal, and reproductive effects. Lead in blood is the best biomarker of lead exposure. No safe blood lead level in children has been identified.(1,2) Detection of very low levels of lead in blood is limited by laboratory methods.(3)

Lead is absorbed primarily by inhalation or ingestion.(2) The leading exposure source in children in the United States is lead-based paint dust in houses built before 1978.(2) The leading exposure source in adults is from work.(4)

Reporting of blood lead test results by clinical laboratories to public health departments is the basis for surveillance for lead exposure. It is mandated in all states, although states’ reporting requirements vary related to age and blood lead level.(5)

Laboratory Criteria

Confirmatory laboratory evidence:

• Detection of lead in a venous blood specimen, tested by graphite furnace atomic absorption spectrometry (GFAAS) or inductively coupled plasma mass spectrometry (ICP/MS), that is at or above the reference value of 3.5 μg/dL.
• Detection of lead in two capillary^‡‡ blood specimens from a child less than 16 years old at or above the reference value of 3.5 μg/dL that are collected within 12 weeks of each other.

Supportive laboratory evidence:

• Detection of lead in a single capillary blood specimen from a child less than 16 years old that is at or above the reference value of 3.5 μg/dL, OR
• Detection of lead in two capillary blood specimens from a child less than 16 years old at or above the reference value of 3.5 μg/dL that are collected after 12 weeks of each other.

^‡‡If specimen type is unknown, it should be considered capillary for persons <16 years of age and venous for persons ≥16 years of age, for the purpose of case classification.

Criteria to Distinguish a New Case from an Existing Case

Many individuals receive more than one blood lead test over time. Individuals who meet the confirmed case classification criteria should be counted as a case only once annually. To distinguish which are new cases to be enumerated annually from those that persist or recur for more than one year, the following should be applied:

• For children (less than age 16) and adults (age 16 years or older): A confirmed case based on a venous test should be enumerated once per calendar year as a new case if the case was not enumerated as a confirmed case in the previous calendar year.

    OR

• For children (less than age 16): A confirmed case based on two capillary tests within 12 weeks of each other should be enumerated once per calendar year as a new case if the case was not enumerated as a confirmed case in the previous calendar year.
  • If the collection date of the second of the two capillary tests occurred in the subsequent calendar year, the case should be counted in the year of the first collection date.

Suspect

Meets the supportive laboratory evidence.

Confirmed

Meets the confirmatory laboratory evidence.