Porphobilinogen (PBG), Quantitative, 24-Hour Urine
| Porphobilinogen (PBG), Quantitative, 24-Hour Urine | | | |
| Number | | 003103 |
| CPT | | 84110 |
| Related Information | | Porphobilinogen (PBG), Quantitative, Random Urine Urine Testing: Preservative Quick Reference Chart |
| Synonyms | | PBG, Quantitative, 24-Hour Urine ; Quantitative Porphobilinogen, 24-Hour Urine |
| Special Instructions | | Record total 24-hour urine volume on the request form. Use test 003053 for random urine. |
| Specimen | | Urine (24-hour), frozen and protected from light |
| Volume | | 10 mL aliquot |
| Minimum Volume | | 1 mL aliquot |
| Container | | Plastic 24-hour urine container with 30 mL of 30% glacial acetic acid. Use amber plastic cup and amber top; order LabCorp No 20656. (If amber cups are unavailable, cover plastic container completely, top and bottom, with aluminum foil. Identify specimen with patient name directly on the container and on the outside of the aluminum foil. Secure with tape.) |
| Collection | | Instruct patient to void at 8 AM (or 8 PM) and discard the specimen. Then collect all the urine including the final specimen voided at the end of the 24-hour collection period (ie, 8 AM (or 8 PM) the following day). Specimen must be kept refrigerated during collection. Label container with patient's name, and date and time collection started and finished. Measure and record total urine volume. Mix well; send aliquot to laboratory. |
| Storage Instructions | | Freeze immediately and protect from light. Urine is stable when preserved with sodium carbonate to pH of 8 and frozen to up to 8 months or when refrigerated for up to 72 hours. Stable when preserved with 30% glacial acetic acid and frozen for up to 1 month and when refrigerated for up to 24 hours. |
| Causes for Rejection | | Specimen not refrigerated during collection; specimen not protected from light; specimen not a 24-hour collection; specimen not frozen; improper or no preservative |
| Reference Interval | | 0.0-1.5 mg/24 hours |
| Use | | Porphobilinogen levels in the urine should be measured during acute attacks of abdominal pain, extremity pain or paresthesias, tachycardia, nausea and vomiting, neurologic abnormalities, and to investigate dark urine. It is an initial test for acute intermittent porphyria, which is characterized by urinary excretion of porphobilinogen and delta aminolevulinic acid during acute attacks. Increased urinary excretion of porphobilinogen may be caused also by acute attacks of variegate porphyria or of hereditary coproporphyria, and also in lead poisoning (rarely). In lead poisoning, urinary aminolevulinic acid measurement is more useful. |
| Methodology | | Ion-exchange chromatography/spectrophotometry |
| Additional Information | | Acute attacks of acute intermittent porphyria are precipitated by drugs, including barbiturates, hydantoins, hormones, infection, and diet. The most common symptom of acute intermittent porphyria is abdominal pain. The most common sign is tachycardia.1 Subjects with the porphyrias may pass urine the color of port wine. The term porphyria derives from the Greek “porphyria,” an expression for the color purple.1 Quantitative porphobilinogen will pick up many but not all patients with acute intermittent porphyria in the latent period. |
| Footnotes | | - Bloomer JR and Bonkovsky HL, “The Porphyrias,” Dis Mon, 1989, 35(1):1-54
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