Sign in →

Test Code PBGD_ Porphobilinogen Deaminase, Whole Blood

Reporting Name

PBG Deaminase, WB

Useful For

Confirmation of a diagnosis of acute intermittent porphyria

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Whole blood


Ordering 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. Patient’s age is required

2. 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.

Container/Tube:

Preferred: Green top (sodium heparin)

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

Specimen Volume: 4 mL

Collection Instructions: Refrigerate specimen as soon as possible.


Specimen Minimum Volume

3 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole blood Refrigerated (preferred) 8 days
  Ambient  7 days

Reference Values

Reference ranges have not been established for patients who are younger than 16 years.

 

≥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
PBGD_ PBG Deaminase, WB 12810-8

 

Result ID Test Result Name Result LOINC Value
4022 PBG Deaminase, WB 12810-8
28400 Interpretation 59462-2
606470 Reviewed By 18771-6

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.

Cautions

A normal result does not rule-out acute intermittent porphyria; 5% to 10% of affected individuals will have normal erythrocyte porphobilinogen deaminase activity. Additionally, enzyme activity may be increased during an acute attack; therefore, the enzyme level should be assessed when the patient is asymptomatic.

Report Available

2 to 8 days

Reject Due To

Gross hemolysis Reject

Method 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.