In evaluating lead exposure in a child, which measurement is essential to confirm exposure status?

• A. Urine lead level.
• B. Blood lead level.
• C. Hair lead level.
• D. Nail lead level.

Answer: (B)

Measuring lead in the blood is the definitive way to confirm exposure in a child. Blood lead level reflects recent exposure and the amount of lead circulating in the body, making it the validated test clinicians use to screen, diagnose, and guide treatment or exposure-reduction efforts. Urine lead level isn’t reliable for confirming exposure because lead excretion in urine varies and a single measure doesn’t accurately represent body burden. Hair or nail lead levels aren’t standardized or trusted for diagnostic purposes and can be influenced by external contamination, so they aren’t used to confirm exposure status. When drawing blood, a venous sample is preferred for accuracy, though a capillary sample may be used for initial screening and should be confirmed with venous testing if indicated.