Since lead toxicity has historically been a significant public health issue, many testing modalities and specimen types have been used to assess lead exposure. As late as 10 years ago, many labs measured lead using anodic stripping voltammetry (ASV). However, as with other heavy metals, Inductively Coupled Plasma Tandem Mass Spectrometry (ICP-MS/MS) is used for detection in all specimen types. Protein or enzyme tests for lead are not commonly used anymore due to the sensitivity and ease of ICP-MS/MS testing. Aminolevulinic acid dehydratase (ALAD) activity is still being measured by some reference labs but is now used as a test to detect genetic ALAD deficiency rather than for lead exposure.
Blood lead:
Because lead accumulates in erythrocytes, whole blood is the specimen of choice for testing. The current reference level at which the CDC recommends initiating public health actions is 3.5 μg/dL for patients 0 to 5 years old and 5 μg/dL for patients 6 years and older. Drug treatment (chelation therapy) can be used to help remove lead from the body and is indicated in children when whole blood lead concentrations are above 25 μg/dL.
Urine lead:
Urine can be used to detect acute lead exposure but is not recommended for the diagnosis of lead toxicity.
Hair lead:
Hair analysis can be used to corroborate blood analysis or to document past lead exposure. If the hair is collected or segmented in a time sequence (based on the length from the root), the approximate time of exposure can be ascertained. It should be noted that hair is subject to external contamination with environmental lead and specific hair treatments (i.e., some hair dyes). Hair testing is uncommon in the clinical setting and is reserved for forensic or long-term exposure assessments rather than routine differential diagnosis of lead toxicity.
Nail lead:
Like hair, fingernails are subject to potential external contamination with environmental lead. But nail testing can be used to help assess long-term exposure. Nail testing is not commonly performed in patients suspected of lead toxicity.
