Environmental Health Center
What is an EP or ZPP level?
EP level stands for erythrocyte protoporphyrin. Another term that is commonly used is zinc protoporphyrin or ZPP. In the past, this test was also known as a free erythrocyte protoporphyrin (FEP).
EP is a chemical that everyone makes in the process of creating new red blood cells (red blood cells carry oxygen in the blood). In children with high lead levels, EP becomes elevated because lead interferes with the creation of red blood cells. Screening by measuring this chemical in the blood [erythrocyte protoporphyrin (EP)] is done every time your child has a lead level drawn.
Why is the EP tested when my child has a lead test?
The EP helps to determine whether the lead in the child's system is having any type of effect on the body that we can measure. EP is one of the only ways to look for an effect of lead on the child. By looking at EP we can get a better idea of how much lead is in the body. Another way to think about EP is this: because EP is made in the body's tissues, if EP is elevated, it suggests that other body tissues (such as the kidney or brain) are also being affected by the lead.
The EP can sometimes also be used to determine for how long the child was exposed to lead. It can also determine whether the child is still being exposed to lead; when children have another exposure to lead, the EP will rise. Finally, the EP helps the doctor to manage the child's lead poisoning; as the lead poisoning is treated (for example, with chelation), the EP falls to the normal range.
How do I interpret it?
The normal range for ZPP is 0-35.
Does anything else raise your EP?
Iron deficiency can also raise your child's EP. So, if your child is anemic he/she may have an elevated EP from anemia and not from lead poisoning. Still, the EP is very useful for a few reasons. First, even though iron deficiency and lead poisoning both raise EP, you can usually tell which of these is responsible. Second, if an EP is elevated because the child has iron deficiency, the doctor can immediately start giving iron supplements to correct the deficiency.