At a Glance
Why Get Tested?
To screen for and monitor chronic exposure to lead; to detect iron deficiency in children
When to Get Tested?
When you have been chronically exposed to lead, as part of a programme to monitor lead exposure, and/or when your doctor suspects lead poisoning; as part of a screening programme for iron deficiency in children and adolescents
A blood sample drawn from a vein in your arm or from a fingerstick
The Test Sample
What is being tested?
The zinc protoporphyrin (ZPP) test is a blood test that can identify a disruption in the formation of haem. Haem is an essential component of haemoglobin, the protein in red blood cells (RBCs) that carries oxygen from the lungs to the bodys tissues and cells. The formation of haem occurs in a series of enzymatic steps that conclude with the insertion of an iron atom into the centre of a molecule called protoporphyrin. If there is not enough iron available, then protoporphyrin combines with zinc instead of iron to form zinc protoporphyrin. Since it cannot transport oxygen, ZPP serves no useful purpose in the RBCs that contain it.
ZPP is measured in two ways. The free erythrocyte protoporphyrin (FEP) test measures both ZPP, which accounts for 90% of protoporphyrin in red blood cells, and free protoporphyrin, which is not bound to zinc. The ZPP/haem ratio gives the proportion of ZPP compared to haem in red blood cells.
How is the sample collected for testing?
To measure FEP, a blood sample is taken by inserting a needle into a vein in your arm. To determine the ZPP/haem ratio, a drop of blood from a fingerstick is placed in an instrument called a haematofluorometer. This instrument measures the fluorescence of ZPP and reports the amount of ZPP per number of haem molecules. Since only a single drop of blood is required, this test is well suited for screening children.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.