PORPHOBILINOGEN DEAMINASE, ERYTHROCYTE

Code
900.3680
Name
PORPHOBILINOGEN DEAMINASE, ERYTHROCYTE
Category
None
Department
Send-Out
Start Date
Expiration Date
Synonyms
PBG-D
CPT Codes
82657
Site
SBMF
Reference Test
44447
ATLAS Test Code

Specimen Information

Type

Lavender, EDTA Whole Blood

Volume

3.0 ml

Transport Info

Do not centrifuge
Do not remove plasma from cells
Refrigerated

Fasting Required?
False
Patient Instructions

Reference Range

Adult: 2.10-4.30 mU/g Hb
Porphobilinogen (PBG) deaminase (hydroxymethylbilane synthase or uroporphyrinogen I synthase) is expressed in units of mU per gram hemoglobin at 37°C. In persons genetically susceptible to acute intermittent porphyria (AIP), PBG deaminase concentrations are approximately half of reference values. Normal concentrations of erythrocyte PBG deaminase may include abnormal forms of hepatic PBG deaminase.
This test is most useful for family studies to determine which family members are at risk for acute intermittent porphyria. It is best performed in association with a specimen from the proband. Because of ambiguous results, this test is not generally recommended for diagnosis of individuals.

Methodology

Quantitative Enzymatic/Fluorometry

Clinical Significance

Porphobilinogen (PBG) deaminase (also called uroporphyrinogen I synthase or hydroxymethylbilane synthase) catalyzes the formation of hydroxymethylbilane from porphobilinogen. In persons genetically susceptible to acute intermittent porphyria (AIP), PBG deaminase levels are approximately half of usual values. Normal concentrations of erythrocyte PBG deaminase, however, may include rare abnormal forms of hepatic PBG deaminase. Since reticulocytes contain higher amounts of this enzyme, hemolytic processes cause an increase in the measured activity. Measurement of porphobilinogen deaminase activity is of limited use in assessing patients with latent acute intermittent porphyria. High urinary excretion of aminolevulinic acid and porphobilinogen are found in overt clinical disease, but these findings are absent in the latent form. PBG deaminase may show decreased activity in gene carriers without overt disease. The recommended approach to the diagnosis of the "acute porphyrias" (e.g., acute intermittent porphyria, hereditary coproporphyria, and variegate porphyria) is to measure urinary PBG. The clinical usefulness of PBG deaminase is limited. This test is most useful for family studies to determine which family members are at risk for acute intermittent porphyria. It is best performed in association with a specimen from the proband. Because of ambiguous results, this test is not generally recommended for studies on an individual.

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