About the Test
Purpose of the test
ZPP is used to monitor chronic exposure to lead in adults. It is also elevated in iron deficiency and may be ordered to help detect this deficiency in children. A ZPP level can be compared with the hemoglobin level to form a ZPP/heme ratio sensitive to diagnosing iron deficiency.
Lead exposure in adults
ZPP testing may be ordered along with a lead level to test for chronic lead exposure. Hobbyists who work with products containing lead — and people, especially children who live in older houses built before 1960 — may have been exposed to lead-based paint products and can be at increased risk for lead poisoning.
Inhaling or ingesting lead dust particles from lead batteries, lead pipe-contaminated water, certain leaded fuels, and foods transported in lead-soldered containers can also cause elevated lead levels.
In an industrial setting, the Occupational Safety & Health Administration (OSHA) mandates the use of the ZPP test and strongly recommends it every time a lead level is ordered to monitor an employee’s exposure.
Both are necessary because ZPP will not reflect recent or acute lead exposure, as it does not change quickly when your source of lead exposure is removed. ZPP is best at detecting your average exposure to lead over the last three to four months.
Also, ZPP is not sensitive enough for use as a lead screening test in children, as values do not rise until lead concentrations exceed the acceptable range. The Centers for Disease Control and Prevention (CDC) set the maximum lead concentration considered safe in children at a very low level. In this age group, tests that directly measure the blood lead concentration are done to detect exposure to lead.
Iron deficiency anemia in children
The ZPP/heme ratio in children is sometimes ordered as an early indicator of iron deficiency. An increase in the ZPP/heme ratio is one of the first signs of insufficient iron stores and will be elevated in most young people before signs or symptoms of anemia are present. More specific tests of iron status are required to confirm an iron deficiency.
In adults, chronic inflammatory diseases such as rheumatoid arthritis, diabetes, and cancer are frequently accompanied by anemia and increase in blood ZPP, partially due to impairment of iron metabolism.
What does the test measure?
To understand how lead poisoning and iron deficiency affect the ZPP level, it is necessary to know about heme. This is an essential component of hemoglobin, the protein in red blood cells that carries oxygen from the lungs to the body’s tissues and cells.
Heme formation occurs in a series of steps that concludes with inserting an iron atom into the center of a molecule called protoporphyrin. When there is not enough iron available, as in iron deficiency, or when the insertion of iron is inhibited, as in lead poisoning, protoporphyrin combines with zinc instead of iron to form ZPP. This serves no useful purpose in red blood cells since it cannot bind to oxygen.
Erythrocyte protoporphyrin (EP) accumulates in red blood cells when insufficient iron is present for proper heme synthesis. A small percentage of EP may be unbound and can be measured as free erythrocyte protoporphyrin (FEP), with the remaining EP (about 90%) measured as ZPP.
When should I get this test?
ZPP may be ordered along with a lead test when chronic exposure to lead is known or suspected in adults. Signs and symptoms of lead poisoning include:
- High blood pressure
- Numbness and/or tingling in the hands and feet
- Memory loss, mood disorders, cognitive impairment
- Abdominal pain, constipation
The test may be ordered when as an employee, you are a participant in an occupational lead monitoring program or if you have a hobby, such as working with stained glass, that brings you into frequent contact with lead.
The ZPP/heme ratio may be ordered as a screening test for iron deficiency in children and adolescents or when iron deficiency is suspected. Some symptoms of iron deficiency include:
- Chronic fatigue, tiredness
If the iron deficiency anemia is severe, shortness of breath, dizziness, chest pain, headaches, and leg pains may occur. Children may develop learning (cognitive) disabilities. Besides the general symptoms of anemia, certain symptoms are characteristic of longtime iron deficiency.
These include pica (cravings for specific substances, such as licorice, chalk, dirt, or clay), a burning sensation in the tongue or a smooth tongue, sores at the corners of the mouth, and spoon-shaped fingernails and toenails. Difficulty swallowing may also occur due to abnormality in the esophagus.
Finding a Zinc Protoporphyrin Test
How can I get a Zinc Protoporphyrin test?
ZPP levels are measured with a blood sample taken from a vein in your arm or a fingerstick. The test is usually performed in a doctor’s office, a hospital, or a laboratory.
Testing is normally done after being prescribed by a doctor or other health professional. You can also order a workplace ZPP test online.
Can I take the test at home?
You can order a ZPP test at-home, but you’ll need to visit a local laboratory to have your sample collected.
How much does the test cost?
The cost of a ZPP test can change based on several factors, including if ZPP is measured alone or as part of a panel, where the sample is collected, and your health insurance coverage.
Your insurance company may pay for some or all of these costs if your doctor prescribes your ZPP test. For the most definitive information about likely costs, talk with your doctor’s office and medical insurance company.
Taking a Zinc Protoporphyrin Test
For ZPP blood tests, a blood sample is typically taken in a medical lab, hospital, or doctor’s office.
Before the test
There are generally no test preparations needed, but check with your doctor to confirm this before the blood draw.
During the test
For a ZPP blood test, a blood sample will be taken from a vein in your arm or using a fingerstick. When drawn from your arm, an elastic tourniquet will be tied around your upper arm to increase blood flow in your arm and make it easier for the technician to access the vein.
The technician will first rub an antiseptic wipe over your skin near the vein, then insert a needle. Once a vial of blood has been withdrawn, the needle will be taken out.
The total blood draw usually lasts only a few minutes. There may be some pain during the procedure, but for most people, it’s just a brief sting when the needle is inserted.
For a fingerstick test, your doctor will use a needle to prick your finger and collect a few drops for the sample.
After the test
You can return to most normal activities once the test is over. Slight pain or bruising can affect your arm if a vein was used for the blood sample, but normally this goes away quickly.
Zinc Protoporphyrin Test Results
Receiving test results
In most cases, results for ZPP tests are available within a few business days.
You may receive your results by mail or online health portals. You may also receive a call or email from your doctor to either review your results or schedule a follow-up appointment.
Interpreting test results
The ZPP concentration in blood is usually very low. An increase in ZPP indicates disruption of normal heme production but is not specific as to its cause. The main reasons for increases in ZPP are iron deficiency and lead poisoning.
ZPP levels must be evaluated in the context of your history, clinical findings, and the results of other tests such as ferritin, lead, and a complete blood count (CBC). You may have both iron deficiency and lead poisoning.
In cases of chronic lead exposure, ZPP reflects the average lead level over the previous three to four months. However, the amount of lead currently present in the blood and the amount in the organs and bones cannot be determined with a ZPP test. Values for ZPP rise more slowly than blood lead concentrations following exposure and take longer to drop after exposure to lead has ceased.
An increase in a child’s ZPP/heme ratio is most often due to iron deficiency. A decreasing ZPP/heme ratio over time following iron supplementation likely indicates successful treatment.
ZPP can also be elevated in anemia caused by chronic inflammatory diseases, infections, and cancer, but it is not generally used to monitor or diagnose these diseases.
Depending on the method used to test ZPP, high levels of other substances in the blood, such as bilirubin and riboflavin, can produce false-positive results. Falsely low values may occur if the sample is not protected from light before testing.
When you talk with your doctor, some of these questions may be helpful to review so you can better understand your test results:
- Was my ZPP level low, normal, or high?
- Were any other measurements taken along with ZPP? If so, were they normal or abnormal?
- If my ZPP was too high or too low, what is the most likely cause?
- Are there any follow-up tests that you recommend?
- Should I have another ZPP test?
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