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HelpTest Code PBGU Porphobilinogen, Quantitative, Random, Urine
Reporting Name
Porphobilinogen, QN, Random, UUseful For
First-order test for evaluating a suspected acute porphyria: acute intermittent porphyria, hereditary coproporphyria, and variegate porphyria
Testing Algorithm
For more information see:
-The Heme Biosynthetic Pathway
Method Name
Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
UrineShipping Instructions
Ship specimen protected from light.
Necessary Information
Include a list of medications the patient is currently taking.
Specimen Required
Patient Preparation: Patient must not consume any alcohol for at least 24 hours prior to collection.
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 above 5.0.
3. Specimens should be protected from light and frozen immediately following collection.
Specimen Minimum Volume
15 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Urine | Frozen (preferred) | 7 days | LIGHT PROTECTED |
| Refrigerated | 7 days | LIGHT PROTECTED |
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Special Instructions
Reference Values
≤1.3 mcmol/L
Day(s) Performed
Monday through Friday
CPT Code Information
84110
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| PBGU | Porphobilinogen, QN, Random, U | 2811-8 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 29365 | Porphobilinogen, U | 2811-8 |
| 29366 | Interpretation (PBGU) | 59462-2 |
| 35032 | Reviewed By | 18771-6 |
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 (PBGD_ / Porphobilinogen Deaminase, 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 (APGP / Acute Porphyria Gene Panel, Varies), 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.
For more information, see the following or call 800-533-1710 to discuss testing strategies:
-The Heme Biosynthetic Pathway
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.
Cautions
It is recommended that specimen collection occur during the acute phase. Porphobilinogen (PBG) may be normal when the patient is not exhibiting symptoms.
If the specimen is collected after treatment is initiated, the level of PBG excreted may be decreased.
Specimens should be protected from light and frozen immediately following collection. PBG is susceptible to degradation at high temperatures, at pH below 5.0, and on prolonged exposure to light.
Method Description
Porphobilinogen (PBG) in urine is quantified by liquid chromatography tandem mass spectrometry after addition of stable isotope-labeled PBG internal standard and solid phase extraction.(Ford RE, Magera MJ, Kloke KM, et al. Quantitative measurement of porphobilinogen in urine by stable-isotope dilution liquid chromatography-tandem mass spectrometry. Clin Chem. 2001 September;47[9]:1627-1632; Stolzel U, Doss MO, Schuppan D. Clinical guide and update on porphyrias. Gastroenterology. 2019;157(2):365-381.e4. doi:10.1053/j.gastro.2019.04.050)
Report Available
2 to 4 daysTest 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.Disease States
- Porphyria