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Test Code UPGDW Uroporphyrinogen Decarboxylase, Washed Erythrocytes

Reporting Name

UPG Decarboxylase, RBC

Useful For

Diagnosis of porphyria cutanea tarda type II and hepatoerythropoietic porphyria

Testing Algorithm

A stepwise approach is typically most effective when evaluating patients with suspected porphyria. See Porphyria (Cutaneous) Testing Algorithm or call 800-533-1710 to discuss testing strategies. If guidance is needed for an acute form of porphyria, the Porphyria (Acute) Testing Algorithm is also available.

Method Name

High-Performance Liquid Chromatography (HPLC)

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Washed RBC


Ordering Guidance


Porphyria cutanea tarda (PCT) type I (sporadic), the most common form of PCT, exhibits normal erythrocyte enzyme activity. The preferred test for diagnosis of PTC type 1 is PQNU / Porphyrins, Quantitative, 24 Hour, Urine or PQNRU / Porphyrins, Quantitative, Random, Urine.



Necessary Information


Include a list of medications the patient is currently taking.



Specimen Required


Patient Preparation: For 24 hours before specimen collection, patient must not consume any alcohol. This is essential as alcohol suppresses enzyme activity for 24 hours after ingestion.

Collection Container/Tube:

Preferred: Green top (sodium heparin)

Acceptable: Lavender top (EDTA) or green top (lithium heparin)

Submission Container/Tube: Plastic vial

Specimen Volume: Entire washed erythrocyte suspension

Collection Instructions:

Collect and process whole blood specimen as follows:

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

2. Centrifuge specimen at 4° C for 10 minutes at 2000 rpm.

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

4. Discard supernatant plasma.

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

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

7. Transfer washed erythrocytes into a plastic vial and freeze.


Specimen Minimum Volume

Washed and resuspended erythrocytes: 1 mL

Specimen Stability Information

Specimen Type Temperature Time
Washed RBC Frozen (preferred) 14 days
  Refrigerated  14 days
  Ambient  4 days

Reject Due To

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Reference Values

≥1.00 RU (Normal)

0.80-0.99 RU (Indeterminate)

<0.80 RU (Indicative of porphyria cutanea tarda type II)

 

RU = Relative Units

Day(s) Performed

Tuesday

CPT Code Information

82657

LOINC Code Information

Test ID Test Order Name Order LOINC Value
UPGDW UPG Decarboxylase, RBC 49596-0

 

Result ID Test Result Name Result LOINC Value
31892 UPG Decarboxylase, RBC 49596-0
606381 Interpretation 59462-2
606382 Reviewed By 18771-6

Report Available

3 to 9 days

Forms

1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

2. If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.

Test Classification

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