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HelpTest ID: PBGDW Porphobilinogen Deaminase, Washed Erythrocytes
Reporting Name
PBG Deaminase, RBCUseful For
Confirmation of a diagnosis of acute intermittent porphyria using washed erythrocyte specimens
Testing Algorithm
The following algorithms are available:
-Porphyria (Acute) Testing Algorithm
Specimen Type
Washed RBCOrdering Guidance
This test is for diagnosis of acute intermittent porphyria. Porphobilinogen deaminase, also known as uroporphyrinogen I synthase, is commonly confused with uroporphyrinogen III synthase, the enzyme deficient in congenital erythropoietic porphyria (CEP). For CEP cases, order UPGC / Uroporphyrinogen III Synthase (Co-Synthase), Erythrocytes.
Necessary Information
1. Volume of packed cells and total volume of specimen (red cells + saline) are required and must be sent with specimen.
2. Patient's age is required
3. 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 ethanol induces porphobilinogen deaminase activity, which may lead to a false-normal result.
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 packed erythrocytes 2 times by resuspension of at least an equal amount of cold 0.9% saline, mix, and centrifuge for 5 minutes at 2000 rpm, discarding supernatant after each washing.
6. 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 | Special Container |
|---|---|---|---|
| Washed RBC | Frozen (preferred) | 14 days | |
| Refrigerated | 14 days | ||
| Ambient | 48 hours |
Reference Values
Reference ranges have not been established for patients who are younger than 16 years of age.
≥7.0 nmol/L/sec
6.0-6.9 nmol/L/sec (indeterminate)
<6.0 nmol/L/sec (diminished)
Day(s) Performed
Thursday
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.CPT Code Information
82657
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| PBGDW | PBG Deaminase, RBC | 2812-6 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 31944 | PBG Deaminase, RBC | 2812-6 |
| 31945 | Interpretation | 59462-2 |
| BG575 | Total cell Suspension | 94496-7 |
| BG576 | Packed cell volume | 94497-5 |
| 606471 | Reviewed By | 18771-6 |
Genetics Test Information
This test is for diagnosis of acute intermittent porphyria.
Clinical Information
The porphyrias are a group of inherited disorders resulting from enzyme defects in the heme biosynthetic pathway. Acute intermittent porphyria (AIP) is caused by diminished erythrocyte activity of porphobilinogen deaminase (PBGD), also known as uroporphyrinogen I synthase or hydroxymethylbilane synthase (HMBS).
Onset of AIP typically occurs during puberty or later. Individuals may experience acute episodes of neuropathic symptoms. Common symptoms include severe abdominal pain, peripheral neuropathy, and psychiatric symptoms. Crises may be precipitated by a broad range of medications (including barbiturates and sulfa drugs), alcohol, infection, starvation, heavy metals, and hormonal changes. AIP is inherited in an autosomal dominant manner. At-risk family members of patients with a biochemical diagnosis of AIP should undergo appropriate testing. Timely diagnosis is important as acute episodes of AIP can be fatal. Treatment of AIP includes the prevention of symptoms through avoidance of precipitating factors. More than 80% of individuals with a deficiency variant in the HMBS gene remain asymptomatic throughout their lives.
The biochemical diagnosis of AIP is made by demonstrating increased urinary excretion of porphobilinogen (PBG) and is most accurate during an acute episode. In addition, the diagnosis of AIP can be confirmed through the measurement of PBGD enzyme activity in erythrocytes, although 5% to 10% of affected individuals exhibit normal erythrocyte PBGD activity. In addition, molecular genetic confirmation (CGPH / Custom Gene Panel, Hereditary, Next-Generation Sequencing, Varies; specify gene list ID: IEMCP-WCJKC9) is available on a clinical basis and can be particularly helpful in identifying asymptomatic family members at risk of acute symptoms.
The workup of patients with a suspected porphyria is most effective when following a stepwise approach. See Porphyria (Acute) Testing Algorithm or call 800-533-1710 to discuss testing strategies.
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.
Clinical Reference
1. Tortorelli S, Kloke K, Raymond K. Disorders of porphyrin metabolism. In: Dietzen DJ, Bennett MJ, Wong ECC, eds. Biochemical and Molecular Basis of Pediatric Disease. 4th ed. AACC Press; 2010:307-324
2. Nuttall KL, Klee GG. Analytes of hemoglobin metabolism-porphyrins, iron, and bilirubin. In: Burtis CA, Ashwood ER, eds. Tietz Textbook of Clinical Chemistry. 5th ed. WB Saunders Company; 2001:584-607
3. Anderson KE, Sassa S, Bishop DF, Desnick RJ. Disorders of heme biosynthesis: X-linked sideroblastic anemia and the porphyrias. In: Valle DL, Antonarakis S, Ballabio A, Beaudet AL, Mitchell GA. eds. The Online Metabolic and Molecular Bases of Inherited Disease. McGraw-Hill; 2019. Accessed April 19,2024. Available at https://ommbid.mhmedical.com/content.aspx?bookid=2709§ionid=225540906
Report Available
2 to 8 daysMethod Name
Enzymatic End Point/Spectrofluorometric
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.
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