Porphobilinogen Deaminase, Whole Blood
Use
This test is useful for the confirmation of a diagnosis of acute intermittent porphyria (AIP). AIP is an inherited disorder resulting from enzyme defects in the heme biosynthetic pathway, specifically diminished erythrocyte activity of porphobilinogen deaminase (PBGD), also known as uroporphyrinogen I synthase or hydroxymethylbilane synthase (HMBS). Onset typically occurs during puberty or later, with symptoms such as severe abdominal pain, peripheral neuropathy, and psychiatric issues. Accurate and timely diagnosis is crucial as acute episodes can be fatal and the condition is inherited in an autosomal dominant manner. More than 80% of individuals with a deficiency variant in the HMBS gene remain asymptomatic. Biochemical diagnosis is best made by increased urinary excretion of porphobilinogen and enzyme activity measurement in erythrocytes.
Special Instructions
Patient must not consume any alcohol for 24 hours prior to specimen collection to prevent false-normal results. Informed consent is required for New York clients and must be documented on the request form or electronic order. If not ordering electronically, complete, print, and send the Biochemical Genetics Test Request form with the specimen. Clients are informed that the test requires patient’s age and a list of current medications. The laboratory advises consultation of available testing algorithms for related tests.
Limitations
A normal test result does not exclude acute intermittent porphyria as 5% to 10% of affected individuals may have normal erythrocyte porphobilinogen deaminase activity. Enzyme activity might increase during an acute attack, necessitating assessment while asymptomatic. Diagnosis should be supplemented with clinical judgment and possibly further genetic testing to confirm or rule out asymptomatic carrier status within families.
New York Approved
Methodology
Other (Enzymatic End Point/Spectrofluorometric)
Biomarkers
LOINC Codes
- 12810-8
- 12810-8
- 59462-2
- 18771-6
Result Turnaround Time
2-8 days
Related Documents
For more information, please review the documents below
Specimen
Whole Blood
Volume
4 mL
Minimum Volume
3 mL
Container
Green top (sodium heparin) preferred; Lavender top (EDTA) or Green top (lithium heparin) acceptable
Collection Instructions
Refrigerate specimen as soon as possible.
Patient Preparation
Patient must not consume any alcohol for 24 hours prior to specimen collection.
Causes for Rejection
Gross hemolysis
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 7 days |
| Refrigerated | 8 days |