Common Test-Ordering Errors
Part 5: Overordered Tests
Plasma Thiamin
Serum Folate
Zinc Protoporphyrin (ZPP)
Laboratory Assessment of Lead Toxicity
August 2010
However, the test is not specific for lead toxicity. For example, in iron deficiency, because iron is not available for heme synthesis, zinc protoporphyrin also accumulates within red blood cells. Zinc protoporphyrin also is not a very sensitive indicator of lead exposure—it cannot reliably detect exposure to lead at the level necessary to protect children. According to the CDC, and I quote:
"Since erythrocyte protoporphyrin is not sensitive enough to identify more than a small percentage of children with blood lead levels between 10 and 25 microgram per deciliter and misses many children with blood lead levels greater than or equal to 25 microgram per deciliter (McElvaine et al, 1991), measurement of blood lead levels should replace the erythrocyte protoporphyrin test as the primary screening method."
For all these reasons, blood lead is the test of choice for screening children for lead toxicity. In our laboratory, the blood lead test is performed using inductively coupled plasma-mass spectrometry. The assay is sensitive and specific, providing the accurate results that are necessary to identify those children for whom interventions are required.
Because of poor sensitivity and specificity, ZPP is no longer recommended for lead screening in children.
Laboratory Assessment |
Jump to section:
- Introduction
- Testing at Mayo Medical Laboratories
- Common MML Test-Ordering Errors
- Overordered Tests
- Thiamin (Vitamin B1)
- Thiamin (Vitamin B1)
- Folate—Serum and RBC
- Diagnostic Algorithm for Macrocytic Anemia
- Simplified Versions of Vitamin-Dependent Pathways
- Lead Toxicity
- Heme Synthesis*
- Laboratory Assessment of Lead Toxicity
- Conclusion
- Questions?
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