Tests
1st tests to order
whole-blood lead level
Test
Venous whole blood is drawn and submitted using lead-free materials. Samples must be anticoagulated as requested by the laboratory, usually in heparin.
There is no "normal" level, and interventions should begin at the first sign of increased exposure.
A rise in whole-blood lead from 2-3 micrograms/dL to 10 micrograms/dL results in a significant loss of IQ in children; the loss is more pronounced at these concentrations than at levels above 10 micrograms/dL.[27][28][30][55] However, most environmental interventions at these lower levels have not been demonstrated to decrease blood lead, so prevention is key to preventing this IQ loss.
Result
≥3.5 micrograms/dL in children; case definition ≥5 micrograms/dL in an adult (person ≥16 years of age); US Occupational Safety and Health Administration considers an adult blood lead level of ≥25 micrograms/dL to be serious
complete blood count
Test
Iron deficiency anemia may coexist with lead exposure.
Result
variable; may show microcytic hypochromic anemia
serum ferritin
Test
Iron deficiency anemia may coexist with lead exposure.
Result
variable; may be reduced
Investigations to avoid
post-chelator challenge urinary metal testing
Recommendations
Do not use urinary lead measurement, with the administration of a chelating agent prior to testing urine, to diagnose lead toxicity. This is a practice referred to as “chelation challenge” or “provoked urine testing”.[48][56][57]
Rationale
Evidence suggests that the chelation challenge has no better prognostic value than the standard blood lead level. Post-challenge urine metal testing is not validated as the results cannot be compared to normal reference values. Furthermore, it can lead to potentially harmful outcomes.[48][56][57]
hair or nail testing
heavy metal screening test
Recommendations
Do not order broad heavy metal screening tests (spot and 24-hour urine collections) to diagnose lead toxicity.[48]
Rationale
Heavy metal screening tests do not aid with the diagnosis of lead toxicity. In the absence of excessive exposure to other metals, these tests can lead to unnecessary concern when results are outside of a normal range.[48]
Tests to consider
24-hour urine lead with chelation
Test
Not a primary diagnostic tool but is used to determine efficacy of chelation therapy and the need for further chelation.
24-hour urine is collected in a lead-free container for submission to the laboratory.
Result
adequate chelation is defined as lead-to-chelant ratio >1 microgram lead/milligram chelant
abdominal radiographs
Test
Indicated for children or adults suspected of ingesting lead materials.
Result
variable; radio-opaque material may be detected in abdomen
nerve conduction studies
Test
Considered in patients with peripheral neuropathy.
Useful for monitoring disease progression.
Result
variable; may show slowing of nerve conduction velocities
Emerging tests
x-ray fluorescence of long bones
MRI brain
Test
Lead exposure, including during childhood, has been associated with altered brain structure and function.[62][63][64] MRI scanning can be considered; it may show decreased brain volume and alterations in myelination and axonal integrity.[65]
Result
decreased brain volume; altered myelination and axonal integrity
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