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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 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: Patient must not consume any alcohol for 24 hours before specimen collection. 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.
Reject Due To
| All specimens will be evaluated at Mayo Clinic Laboratories for test suitability. |
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Washed RBC | Frozen (preferred) | 14 days | |
| Refrigerated | 14 days | ||
| Ambient | 4 days |
Specimen Minimum Volume
1 mL of washed and resuspended erythrocytes
Special Instructions
Day(s) Performed
Tuesday, Thursday
Specimen Retention Time
14 daysReport Available
2 to 6 daysReference Values
≥1.00 RU (normal)
0.80-0.99 RU (indeterminate)
<0.80 RU (indicative of PCT type II)
RU = Relative Units
Useful For
Diagnosis of porphyria cutanea tarda type II and hepatoerythropoietic porphyria
Testing Algorithm
The workup of patients with a suspected porphyria is most effective when following a stepwise approach. 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 |
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.