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Test ID: PBGU Porphobilinogen, Quantitative, Random, Urine

Reporting Name

Porphobilinogen, QN, Random, U

Useful For

First-order test for evaluation of a suspected acute porphyria: acute intermittent porphyria, hereditary coproporphyria, and variegate porphyria

Testing Algorithm

The following algorithms are available in Special Instructions:

-Porphyria (Acute) Testing Algorithm

-Porphyria (Cutaneous) Testing Algorithm

Specimen Type

Urine


Specimen Required


Supplies: Urine Container-Amber, 60 mL (T596)

Specimen Volume: 20 mL

Collection Instructions:

1. Collect a random urine specimen.

2. No preservative necessary but pH must be >5.0.

3. Specimens should be frozen immediately following collection and protected from light.


Specimen Minimum Volume

15 mL

Specimen Stability Information

Specimen Type Temperature Time
Urine Frozen (preferred) 7 days
  Refrigerated  7 days

Reference Values

≤1.3 mcmol/L

Day(s) and Time(s) Performed

Monday through Friday; 8 a.m.

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

84110

LOINC Code Information

Test ID Test Order Name Order LOINC Value
PBGU Porphobilinogen, QN, Random, U In Process

 

Result ID Test Result Name Result LOINC Value
29365 Porphobilinogen, U 2811-8
29366 Interpretation (PBGU) 59462-2
35032 Reviewed By No LOINC Needed

Clinical Information

The porphyrias are a group of inherited disorders resulting from enzyme defects in the heme biosynthetic pathway. Depending on the specific enzyme involved, various porphyrins and their precursors accumulate in different specimen types. The patterns of porphyrin accumulation in erythrocytes and plasma and excretion of the heme precursors in urine and feces allow for the detection and differentiation of the porphyrias.  

 

The porphyrias are typically classified as erythropoietic or hepatic based upon the primary site of the enzyme defect. In addition, hepatic porphyrias can be further classified as chronic or acute, based on their clinical presentation.

 

The primary acute hepatic porphyrias: acute intermittent porphyria (AIP), hereditary coproporphyria (HCP), and variegate porphyria (VP), are associated with neurovisceral symptoms that typically onset during puberty or later. Common symptoms include severe abdominal pain, peripheral neuropathy, and psychiatric symptoms. A broad range of medications (including barbiturates and sulfa drugs), alcohol, infection, starvation, heavy metals, and hormonal changes may precipitate crises. Photosensitivity is not associated with AIP, but may be present in HCP and VP.

 

Urinary porphobilinogen (PBG) is elevated during the acute phase of the neurologic porphyrias. Urine and fecal porphyrin analysis should be performed to confirm the diagnosis and to distinguish between AIP, HCP and VP. A biochemical diagnosis of AIP can be confirmed by measurement of PBG deaminase activity using PBGD_ / Porphobilinogen Deaminase (PBGD), Whole Blood. VP and HCP can be confirmed by measurement of fecal porphyrins (FQPPS / Porphyrins, Feces). Once the biochemical diagnosis of an acute porphyria is established, molecular genetic testing is available for AIP (HMBSZ / HMBS Gene, Full Gene Analysis), HCP (CPOXZ / CPOX Gene, Full Gene Analysis), or VP (PPOXZ / PPOX Gene, Full Gene Analysis) which allows for diagnosis of at-risk family members.

 

The workup of patients with a suspected porphyria is most effective when following a stepwise approach. See Porphyria (Acute) Testing Algorithm and Porphyria (Cutaneous) Testing Algorithm in Special Instructions or contact Mayo Medical Laboratories 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, and recommendations for additional testing when indicated and available, and a phone number to reach one of the laboratory directors in case the referring physician has additional questions.

Clinical Reference

1. Tortorelli S, Kloke K, Raymond K: Chapter 15: Disorders of porphyrin metabolism. In Biochemical and Molecular Basis of Pediatric Disease. Fourth edition. Edited by DJ Dietzen, MJ Bennett, ECC Wong. AACC Press, 2010, pp 307-324

2. Nuttall KL, Klee GG: Analytes of hemoglobin metabolism-porphyrins, iron, and bilirubin. In Tietz Textbook of Clinical Chemistry. Fifth edition. Edited by CA Burtis, ER Ashwood. Philadelphia, WB Saunders Company, 2001, pp 584-607

3. Anderson KE, Sassa S, Bishop DF, Desnick RJ: X-Linked sideroblastic anemia and the porphyrias. In Disorders of Heme Biosynthesis. Edited by D Valle, AL Beaudet, B Vogelstein, et al. New York: McGraw-Hill; 2014. Accessed June 27, 2016. Available at http://ommbid.mhmedical.com/content.aspx?bookid=971&Sectionid=62638866

Analytic Time

2 days (not reported on Saturday or Sunday)

Method Name

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) Stable Isotope Dilution Analysis

Forms

New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (T576) is available in Special Instructions.

Mayo Medical Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

mml-biochemical