Platform
Company
Immunology & Autoimmune
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Currently under review
Pending specialist review and validation.
This test measures coproporphyrin isomer I in your urine. Coproporphyrins are building blocks used to make heme, a vital component of hemoglobin and many enzymes. The result is reported relative to urine creatinine to account for how concentrated or diluted the urine is.
It is often performed as part of a porphyrin profile to help understand how your body is producing and handling porphyrins. Changes in the amount or pattern of coproporphyrin I can occur with inherited heme synthesis disorders, liver or bile transport problems, and some environmental or medication exposures.
Your clinician may order this test if you have symptoms that raise concern for a porphyria, such as episodic severe abdominal pain, nerve problems, or skin blistering, or if another porphyrin screen is abnormal. Measured together with other porphyrin fractions, it helps narrow the cause and guides the need for further testing.
In infants or people with jaundice, this test can aid in distinguishing benign inherited bilirubin transport conditions from other causes of cholestasis. It can also increase with certain drugs or toxins, so identifying a trigger may help prevent flares or complications.
Your result is interpreted alongside other porphyrin fractions, your symptoms, and your medical history. A higher-than-expected value may reflect increased porphyrin production, reduced excretion into bile, or a shift toward the isomer I pattern that occurs with specific inherited transport conditions and some liver diseases.
If your value is unexpected, your clinician may repeat the test, review medications and exposures, and order complementary studies such as total urine porphyrins, isomer distribution, plasma or fecal porphyrins, or genetic testing. Lower-than-expected values are usually not concerning on their own.
Follow the collection instructions carefully, including light protection, and try to test during active symptoms if advised. Decisions about treatment or further evaluation are based on the overall clinical picture rather than a single laboratory number.
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.
Porphyrins degrade with light and time. Urine should be collected in a light-protected container, kept cool, and delivered promptly to reduce the risk of falsely low results.
Results are normalized to creatinine, but very dilute or very concentrated urine, extreme exercise, or very low muscle mass can still skew the ratio and interpretation.
Porphyrinogenic drugs (for example certain barbiturates, antiepileptics, rifampin, sulfonamides), hormones, alcohol, and heavy metal exposure can raise urinary coproporphyrins. Do not stop medicines without medical advice; bring a full medication list.
Cholestasis, hepatitis, inherited bilirubin transport disorders, and pregnancy-related cholestasis can alter the amount and isomer pattern of urinary coproporphyrins.
Newborns and young infants have different baseline porphyrin excretion and isomer patterns. Laboratories use age-specific interpretation to account for these differences.
Because results are indexed to creatinine, significant renal impairment or very low creatinine output can affect accuracy and may require cautious interpretation.
For suspected acute porphyria, collecting during or soon after symptoms improves diagnostic yield. Testing remote from symptoms may appear normal even with disease.
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