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 diseases that prevent your body from properly making heme, the red pigment that contains iron. 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.
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.
You may need this test if your doctor 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, weight loss, pregnancy, infections, or major surgery. Symptoms include:
Skin problems after sun exposure
Numbness and tingling
Rapid heart rate and high blood pressure
If your first test shows an abnormal level of porphyrin or its precursors, your doctor 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.
Your health care provider might also order a blood or stool test to diagnose porphyria.
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 health care 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.
This test requires a urine simple. Your doctor may recommend a 24-hour sample, which means collecting all the urine you produce 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 health care 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.
The test results may be affected if the urine sample is contaminated in any way.
You don't need to prepare for this test. Be sure your doctor 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.