Test ID: PBGU
Porphobilinogen, Quantitative, Random, Urine
Useful For 
Suggests clinical disorders or settings where the test may be helpful
First-line test for establishing a tentative diagnosis for acute neuropathic porphyria including acute intermittent porphyria, hereditary coproporphyria, and variegate porphyria.
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Urinary porphobilinogen (PBG) is elevated during the acute phase of the neurologic porphyrias: acute intermittent porphyria (AIP), hereditary coproporphyria (HCP), and variegate porphyria (VP). Acute attacks may produce symptoms of cerebral dysfunction and damage (confusion, "psychiatric disease"), autonomic neuropathy, constipation, urinary retention, tachycardia, hypertension, and severe (sometimes chronic) abdominal pain. In the acute phase, these disorders can be life threatening. Between attacks patients have mild symptoms that may include psychoneuroses. Several studies indicate that approximately 1 in 300 psychiatric patients have AIP.
The common symptoms of AIP, HCP, and VP mimic many other diseases from acute appendicitis to acute schizophrenia. Acute episodes usually begin with or include abdominal discomfort ranging from mild cramping to severe pain that suggests a need for surgical intervention. These symptoms and outward signs are common to a variety of medical problems and diagnosis usually depends on timely, accurate laboratory testing. Frequently, surgical intervention can be avoided if the laboratory returns an elevated level for urinary PBG. For additional information on the recommended order of testing, see Porphyria (Acute) Testing Algorithm and Porphyria (Cutaneous) Testing Algorithm in Special Instructions. Refer to The Challenges of Testing For and Diagnosing Porphyrias, Mayo Medical Laboratories Communique 2002 Nov;27(11) for more information regarding diagnostic strategy.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
< or =1.3 mcmol/L
Interpretation Provides information to assist in interpretation of the test results
Increased urinary porphobilinogen (PBG) excretion in the presence of suggestive clinical symptoms is consistent with a biochemical diagnosis of acute porphyria (acute intermittent porphyria [AIP], variegate porphyria [VP], and hereditary coproporphyria [HCP]).
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_/88925 Porphobilinogen (PBG) Deaminase, Whole Blood). VP and HCP can be confirmed by measurement of fecal porphyrins (FQPPS/81652 Porphyrins, Feces).
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Ideally, specimen collection should occur during the acute phase. Porphobilinogen (PBG) may be normal when the patient is not exhibiting symptoms.
PBG is susceptible to degradation at high temperatures, at pH <5.0, and on prolonged exposure to light. Specimens should be frozen immediately following collection and protected from light.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Tefferi A, Colgan JP, Solberg LA Jr: Acute porphyrias: diagnosis and management. Mayo Clin Proc 1994 October;69(10):991-995
2. Mattern SE, Tefferi A: Acute porphyria: the cost of suspicion. Am J Med 1999 December;107(6):621-623
3. Nuttall KL: Teitz Textbook of Clinical Chemistry. 5th edition. Edited by CA Burtis, ER Ashwood. Philadelphia, WB Saunders Company, 1994, pp 2073-2106
External
link
PDF
document
Excel
document
Word
document