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Test Code UPGDW Uroporphyrinogen Decarboxylase (UPG D), Washed Erythrocytes

Reporting Name

UPG Decarboxylase, RBC

Useful For

Diagnosis of porphyria cutanea tarda type II and hepatoerythropoietic porphyria

Testing Algorithm

The following algorithms are available in Special Instructions:

-Porphyria (Acute) Testing Algorithm

-Porphyria (Cutaneous) Testing Algorithm

Method Name

High-Performance Liquid Chromatography (HPLC)/Incubation of Lysed Erythrocytes

Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type

Washed RBC

Advisory Information

This test should only be ordered when the specimen will be received at Mayo Medical Laboratories within 24 hours of collection. The preferred test for analysis of UPGD enzyme is UPGD / Uroporphyrinogen Decarboxylase (UPG D), Whole Blood.


Porphyria cutanea tarda (PCT) type I, the most common form of PCT, exhibits normal RBC enzyme activity. The preferred test for diagnosis is PQNU / Porphyrins, Quantitative, 24 Hour, Urine or PQNRU / Porphyrins, Quantitative, Random, Urine.

Specimen Required

All porphyrin tests on erythrocytes can be performed on 1 draw tube.


Patient Preparation: Patient should abstain from alcohol for 24 hours. Abstinence from alcohol is essential for at least 24 hours as alcohol suppresses enzyme activity for 24 hours after ingestion.

Collection Container/Tube:

Preferred: Green top (heparin)

Acceptable: Lavender top (EDTA)

Submission Container/Tube: Plastic vial

Specimen Volume: Washed erythrocyte suspension

Collection Instructions: Collect and process whole blood specimen as follows:

1. Immediately place specimen on wet ice.

2. Transfer entire specimen to a 12-mL graduated centrifuge tube.

3. Centrifuge specimen for 10 minutes at 2,000 rpm.

4. Record volume of packed cells and the total volume of the specimen.

5. Discard supernatant plasma.

6. Wash erythrocytes 2 times by resuspension with 5 mL of cold 0.9% saline, discarding supernatant after each washing.

7. Resuspend packed cells to the original total volume with 0.9% saline. Invert specimen gently to mix.

Specimen Minimum Volume

1 mL of washed and resuspended erythrocytes

Specimen Stability Information

Specimen Type Temperature Time
Washed RBC Frozen 24 hours

Reject Due To









Reference Values

>1.0 Relative Units (normal)

0.80-0.99 Relative Units (indeterminate)

<0.80 Relative Units (porphyria cutanea tarda or hepatoerythropoietic porphyria)

Day(s) and Time(s) Performed

Tuesday, Thursday; 8 a.m.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
UPGDW UPG Decarboxylase, RBC In Process


Result ID Test Result Name Result LOINC Value
31892 UPG Decarboxylase, RBC 49596-0


Alcohol ingestion within 24 hours of testing may lead to a false-positive result.


Exposure of specimens to significant heat during the summer months may cause a decrease in the UPGD enzyme activity.

Method Description

This procedure is performed by incubation of lysed red cells with delta-aminolevulinic acid as the substrate followed by analysis of the porphyrins formed.(Unpublished Mayo method)

Analytic Time

3 days (Not reported on Saturday or Sunday)

Specimen Retention Time

2 weeks


Abnormal results are reported with a detailed interpretation that may include an overview of the results and their significance, a correlation to available clinical information provided with the specimen, differential diagnosis, recommendations for additional testing when indicated and available, and a phone number to reach one of the laboratory directors in case the referring physician has additional questions.

Clinical Information

The porphyrias are a group of inherited disorders resulting from enzyme defects in the heme biosynthetic pathway. Porphyria cutanea tarda (PCT) is the most common porphyria resulting from a partial deficiency of hepatocyte and/or erythrocyte uroporphyrinogen decarboxylase (UROD). PCT is classified into 3 subtypes. The most frequently encountered is type I, a sporadic or acquired form, typically associated with concomitant disease or other precipitating factors. Patients exhibit normal UROD activity in erythrocytes but decreased hepatic activity. This differs from type II PCT in which patients exhibit approximately 50% activity in both erythrocytes and hepatocytes. Type II accounts for about 20% of cases and is inherited in an autosomal dominant manner with low penetrance. Type III is a rare familial form seen in less than 5% of PCT cases. As in type I, patients with type III PCT have normal UROD activity in erythrocytes with decreased hepatic activity. Type III cases are distinguished from type I by the history of other affected family members.


Hepatoerythropoietic porphyria (HEP) is a rare autosomal recessive form of porphyria that typically presents in early childhood. Patients have a severe deficiency of UROD, with activity levels 10% of normal in both hepatocytes and erythrocytes.


All forms of PCT and HEP result in accumulation of uroporphyrin and intermediary carboxyl porphyrins in skin, subcutaneous tissues, and the liver. The most prominent clinical characteristics are cutaneous photosensitivity and scarring on sun-exposed surfaces. Patients experience chronic blistering lesions resulting from mild trauma to sun-exposed areas. These fluid-filled vesicles rupture easily, become crusted, and heal slowly. Secondary infections can cause areas of hypo- or hyperpigmentation or sclerodermatous changes and may result in the development of alopecia at sites of repeated skin damage. Liver disease is common in patients with PCT as evidenced by abnormal liver function tests and with 30% to 40% of patients developing cirrhosis. In addition, there is an increased risk of hepatocellular carcinoma.


The workup of patients with a suspected porphyria is most effective when following a stepwise approach. See Porphyria (Cutaneous) Testing Algorithm in Special Instructions or contact Mayo Medical Laboratories to discuss testing strategies.

Genetics Test Information

Uroporphyrinogen decarboxylase (UPGD) is deficient in cases of type II porphyria cutanea tarda (PCT). Enzyme analysis is uninformative in sporadic PCT cases.


Due to limited stability for this test, the preferred test for analysis of UPGD enzyme is UPGD / Uroporphyrinogen Decarboxylase (UPG D), Whole Blood.


New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (T576) is available in Special Instructions.

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.