How is lead toxicity diagnosed?

Updated: Jan 16, 2020
  • Author: Pranay Kathuria, MD, FACP, FASN, FNKF; Chief Editor: Tarakad S Ramachandran, MBBS, MBA, MPH, FAAN, FACP, FAHA, FRCP, FRCPC, FRS, LRCP, MRCP, MRCS  more...
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Answer

The criterion standard is a whole blood lead level (BLL). Any BLL greater than 5 µg/dL is considered positive and consequential. Patients with BLLs between 10 and 20 µg/dL require removal from the exposure, repeated testing, and follow-up.

A free erythrocyte protoporphyrin (FEP) level may be useful in demonstrating the degree of biological abnormalities that exist. Significantly elevated BLLs are associated with a microcytic anemia. Iron deficiency, also associated with anemia, may produce an elevation of FEP, confounding the significance of FEP measurement.

Workup guidelines for the use of investigative studies in patients with different BLLs (see below) are based on the recommendations from the Centers for Disease Control and Prevention (CDC) Advisory Committee on Childhood Lead Poisoning Preventions, the National Center of Environmental Health/Agency for Toxic Substances and Disease Registry, and the American Academy of Pediatrics Committee on Environmental Health. [23, 24, 25, 26, 27]

Imaging studies are ordered as appropriate.

Lead may produce subtle nephrogenic effects, which, if unappreciated, may lead to treatment failures or complications. For example, a child may appear to have a mild degree of dehydration based on decreased urine output, increased urine specific gravity, and poor appetite while actually suffering from the syndrome of inappropriate excretion of antidiuretic hormone (SIADH). Such patients have hypo-osmolar hyponatremia and, in fact, are often treated with fluid restriction.


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