Platform
Company
Immunology & Autoimmune
Review status
Currently under review
Pending specialist review and validation.
This test measures the amount of the coproporphyrin I isomer excreted in your urine over a full 24-hour period. Coproporphyrins are intermediates in the pathway that produces heme, the component that helps red blood cells carry oxygen and supports many enzymes throughout the body.
Because porphyrins are sensitive to light and can break down, the urine needs to be collected carefully over 24 hours, kept protected from light, and handled with the preservative your lab provides. Your result is often interpreted together with other porphyrin tests to understand how your body makes, transports, and clears these compounds.
Clinicians order this test when symptoms or findings suggest a porphyria, when there are unexplained liver test abnormalities, dark urine, abdominal pain, or neurologic episodes, or when certain medicines or toxins might be affecting porphyrin handling. It can also provide clues about liver transport problems and reduced bile flow.
The result is most informative when combined with related tests, such as total urinary porphyrins, coproporphyrin III, the isomer I percentage, delta-aminolevulinic acid, porphobilinogen, and sometimes plasma or stool porphyrins. Together, these help determine whether a porphyria is likely, whether the liver or bile ducts are involved, and what next steps are appropriate.
A higher-than-expected value can be seen with impaired bile flow, inherited liver transport disorders, acute illness, heavy metal exposure, alcohol use, or certain medications. Mild elevations are relatively common and do not by themselves confirm a porphyria. Very low results are generally not concerning.
If your result falls outside the expected range, your clinician will consider your symptoms, medication and exposure history, and other lab findings. You may be asked to repeat the collection with careful timing and light protection, or to complete additional tests such as ALA, PBG, fractionated porphyrins, or genetic studies. Interpretation may differ if you are pregnant, a child, or have chronic liver disease, so individualized guidance is important.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Missing urine during the collection period or inaccurate start and stop times can significantly distort the measured daily excretion. Follow the container and timing instructions exactly.
Porphyrins degrade with light and improper pH. Keep the container shielded from light and use any acid preservative supplied by the lab to prevent breakdown and false low results.
Drugs that affect liver transport or enzymes, such as rifampin, estrogens, barbiturates, or some anticonvulsants, as well as herbal products, can alter urinary coproporphyrin levels.
Lead and some other heavy metals, as well as alcohol use, can increase urinary coproporphyrins. Tell your clinician about occupational or environmental exposures and drinking patterns.
Cholestasis and inherited disorders of hepatic transport can raise coproporphyrin I excretion. Recent or chronic liver disease changes may influence your result and its interpretation.
Acute illness, fasting, or physiologic stress can transiently alter porphyrin metabolism. If possible, avoid fasting and note any recent sickness when the sample was collected.
Physiologic changes in pregnancy and developmental differences in children can affect porphyrin results. Your care team may use different interpretive considerations in these settings.
Extremely dilute or concentrated urine can complicate interpretation. Maintain usual hydration and keep the container refrigerated if instructed to do so during the collection period.
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