Plasma and Urine Porphobilinogen (PBG)
Urinary and plasma porphobilinogen (PBG) measurements are used in the clinical diagnosis and monitoring of the acute porphyrias, a group of inborn errors of heme biosynthesis. These include autosomal dominant acute intermittent porphyria (AIP), hereditary coproporphyria (HCP) and variegate porphyria (VP) and autosomal recessive ALA-dehydratase deficient porphyria (ADP). Gene mutations alone are not sufficient to produce the symptoms of these disorders; other activating factors, such as drugs, hormones, and dietary changes must be present. The characteristic acute attacks almost always start with severe pain in the abdomen but sometimes in the chest, back, or thighs, and are often accompanied by nausea, vomiting, and constipation. Heart rate and blood pressure are commonly increased. These symptoms and signs are all due to the effects of the disease on the nervous system. Confusion, convulsions, and muscular weakness, due to impairment of the nerves controlling the muscles, may lead to paralysis. An acute attack usually lasts for days or weeks. Recovery from severe paralysis is generally slow.
The diagnostic hallmark of an acute attack is the marked increase of plasma and urinary concentrations of the porphyrin precursors, ALA and PBG, particularly urinary PBG. In the three autosomal dominant acute porphyrias, ALA and PBG levels are normal or slightly increased in asymptomatic patients, but maybe increased 200-fold over presymptomatic levels during an acute attack. In ADP, the ALA levels are consistently elevated, but increases occur during acute attacks. Testing is performed by liquid chromatography and tandem mass spectrometry. This test is commonly ordered with urinary and plasma aminolevulinic acid (ALA).
Plasma: 3 ml blood in sodium heparin (green top) tube. Draw in amber tube or protect from light by wrapping in foil. Separate the plasma immediately and freeze.
Urine: 2-5ml urine (random void) in clean container without preservatives. Protect from light by wrapping in foil. Freeze.
Shipping: Ship urine and/or plasma overnight frozen on dry ice.
Turnaround Time: 5 days for routine samples.
Same day results available on an emergency basis. Please call the laboratory prior to sending a sample for STAT analysis.
CPT Codes: 84110, 83789
Consent Form: Biochemical Consent [PDF]
Requisition Form: General Test Requisition [PDF]