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HelpTest Code UPGDW Uroporphyrinogen Decarboxylase, Washed Erythrocytes
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Reporting Name
UPG Decarboxylase, RBCSpecimen Type
Washed RBCOrdering 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.
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Washed RBC | Frozen (preferred) | 14 days |
| Refrigerated | 14 days | |
| Ambient | 4 days |
Specimen Minimum Volume
Washed and resuspended erythrocytes: 1 mL
Special Instructions
Day(s) Performed
Tuesday
Specimen Retention Time
14 daysReport Available
3 to 9 daysReference Values
≥1.00 RU (Normal)
0.80-0.99 RU (Indeterminate)
<0.80 RU (Indicative of porphyria cutanea tarda type II)
RU = Relative Units
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.
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 |
Method Description
This procedure is performed by incubation of lysed red blood cells with aminolevulinic acid as the substrate followed by analysis of the porphyrins formed.(Unpublished Mayo method)
Genetics Test Information
Uroporphyrinogen decarboxylase is deficient in cases of type II porphyria cutanea tarda (PCT). Enzyme analysis is uninformative in sporadic PCT cases.
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.