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Test Code UPGC Uroporphyrinogen III Synthase (Co-Synthase) (UPG III S), Erythrocytes

Reporting Name

Uroporphyrinogen III Synthase, RBC

Useful For

Diagnosis of congenital erythropoietic 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)

Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type

WB Heparin


Advisory Information


This test is most appropriately used for pediatric patients.

 

This test measures uroporphyrinogen (UPG) III synthase to confirm congenital erythropoietic porphyria, which is typically seen in early infancy. It does not measure UPG I synthase (also known as porphobilinogen deaminase), the enzyme deficient in acute intermittent porphyria (AIP). For AIP (and UPG I synthase), order PBGD_ / Porphobilinogen (PBG) Deaminase, Whole Blood.



Necessary Information


1. Physician name and phone number are required. Due to the high frequency of incorrect test orders, all UPGC test requests are confirmed by a genetic counselor as appropriate prior to the test being run. A letter is faxed to the ordering physician with options for alternative testing. If a response is not received from the physician within 1 week, the test will be canceled and the specimen will be held for 1 month.

2. Include a list of medications the patient is currently taking.



Specimen Required


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

 

Patient Preparation: Patient should abstain from alcohol for 24 hours.

Container/Tube: Green top (heparin)

Specimen Volume: Full tube

Collection Instructions:

1. Patient should abstain from alcohol for 24 hours.

2. Immediately place specimen on wet ice.

Additional Information:

1. Include a list of medications the patient is currently taking.

2. This test is most appropriately used for pediatric patients.

3. Due to the high frequency of incorrect test orders, all UPGC test requests are confirmed by a genetic counselor as appropriate prior to the test being run. A letter is faxed to the ordering physician with options for alternative testing. If a response is not received from the physician within 1 week, the test will be canceled and the specimen will be held for 1 month.


Specimen Minimum Volume

3 mL

Specimen Stability Information

Specimen Type Temperature Time
WB Heparin Refrigerated 7 days

Reject Due To

Hemolysis

Mild reject; Gross reject

Lipemia

NA

Icterus

NA

Other

Ambient or frozen whole blood

Reference Values

≥75 Relative Units (normal)

 

See The Heme Biosynthetic Pathway in Special Instructions.

Day(s) and Time(s) Performed

Varies

The order for this test is confirmed by a genetic counselor prior to the test being run.

CPT Code Information

82657

LOINC Code Information

Test ID Test Order Name Order LOINC Value
UPGC Uroporphyrinogen III Synthase, RBC In Process

 

Result ID Test Result Name Result LOINC Value
80288 Uroporphyrinogen III Synthase, RBC 11066-8

Analytic Time

7 days (Not reported on Saturday or Sunday)

Interpretation

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 a laboratory director in case the referring physician has additional questions.

Cautions

This test is not useful for ruling out acute intermittent porphyria (AIP) a disorder caused by decreased uroporphyrinogen I synthase (also known as porphobilinogen deaminase). For AIP, order PBGD_ / Porphobilinogen Deaminase (PBGD), Whole Blood.

 

This test does not reliably distinguish between individuals who are carriers for congenital erythropoietic porphyria (CEP), and are at risk for having an affected child.

 

If possible, specimens from patients suspected of having CEP should be drawn prior to blood transfusions; uroporphyrinogen (UPG) III synthase activity in transfused erythrocytes can cause false-negative results.

 

Abstinence from alcohol for at least 24 hours is essential for accurate results. While the effects of alcohol on this enzyme have not yet been determined, alcohol is known to suppress or induce other enzymes in the heme biosynthetic pathway.

Method Description

Washed cells are incubated with aminolevulinic acid as substrate and the series I and III porphyrin isomers formed are measured. The proportion of series III isomers formed in relation to total porphyrins (I + III isomers) represents the uroporphyrinogen III synthase activity. The values are reported as Relative Units.(Unpublished Mayo method)

Clinical Information

The porphyrias are a group of inherited disorders resulting from enzyme defects in the heme biosynthetic pathway. Congenital erythropoietic porphyria (CEP) is an extremely rare, autosomal recessive porphyria that typically presents in early infancy. Also known as Gunther disease, CEP results from a deficiency of uroporphyrinogen III (co-) synthase (UROIIIS). In most cases, the disorder is suggested during the first few days or weeks of life by pink, violet, or brown urinary staining of diapers. Clinical symptoms include hemolytic anemia, hepatosplenomegaly, skin photosensitivity, scarring and blistering, red or brown dental discoloration (erythrodontia), and hypertrichosis (excess body hair). Growth and cognitive developmental delays are commonly observed in individuals with CEP. A few cases of adult-onset CEP have been reported, typically associated with a myelodysplastic syndrome.

 

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.

Specimen Retention Time

2 weeks

Genetics Test Information

This test is not appropriate for assessment of acute abdominal pain.

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.

Forms

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.