Does this test have other names?
What is this test?
This test looks for chemicals called porphyrins in your urine. If you have high levels of these chemicals, you may have porphyria.
Porphyria refers to a group of inherited or acquired diseases that prevent your body from properly making heme, the red pigment that contains iron. Heme is made in the bone marrow and liver. A large amount of heme is present as hemoglobin in red blood cells and bone marrow. Hemoglobin carries oxygen throughout the body. Eight enzymes are needed to create heme, and if any are lacking, the result can be a type of porphyria. Porphyria is rare and is usually inherited. Acquired porphyria may result from iron or lead toxicity, alcohol use, hepatitis C, HIV, and some medicines.
Porphyrins and related chemicals are made in your body as part of the process of making heme. Certain types of porphyria cause these chemicals to pass into your urine.
Why do I need this test?
You may need this test if your healthcare provider suspects that you have porphyria. Porphyria can affect the nervous system or skin. Sometimes both are affected. The condition may or may not cause symptoms. Symptoms may develop over hours or days and last for days or weeks. Symptoms may be brought on by various medicines, smoking, drinking alcohol, weight loss, pregnancy, infections, or major surgery. Symptoms include:
Skin problems after sun exposure
Pain, especially belly (abdominal) pain
Numbness and tingling
Rapid heart rate and high blood pressure
If your first test shows an abnormal level of porphyrin or its precursors, your healthcare provider may order a second test to confirm the results.
Lead can also show up in urine, so this test may be used if your provider suspects you have lead poisoning.
This test may also be ordered to monitor your response to treatment for porphyria.
What other tests might I have along with this test?
Your healthcare provider might also order a DNA test or blood or stool tests to diagnose porphyria.
What do my test results mean?
Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your healthcare provider.
Different substances can be present at different levels in your urine, depending on the type of porphyria you have. For example, levels of a porphyrin precursor called porphobilinogen, or PGB, above 6 milligrams (mg) per day in your urine may mean acute intermittent porphyria, variegate porphyria, or hereditary coproporphyria.
How is this test done?
This test requires a urine sample. Your healthcare provider may recommend a spot urine sample or a 24-hour sample. A 24-hour sample means collecting all the urine you make in 24 hours. For this test, empty your bladder completely first in the morning without collecting it and note the time. Then collect your urine every time you go to the bathroom over the next 24 hours.
Follow your healthcare provider's instructions for collecting and storing the urine. Keep it out of bright light and store it in a cool place, like the refrigerator.
What might affect my test results?
The test results may be affected if the urine sample is contaminated in any way.
How do I get ready for this test?
You don't need to prepare for this test. Be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.
- Freeborn, Donna, PhD, CNM, FNP
- Hanrahan, John, MD