Porphyrins, Fractionated, Quantitative and Porphobilinogen, 24-Hour Urine

17198

Porphyrins, Fractionated, Quantitative, 24-Hour Urine (Coproporphyrin I, Coproporphyrin III, Heptacarboxyporphyrin, Hexacarboxyporphyrin, Pentacarboxyporphyrin, Uroporphyrin I, Uroporphyrin III, Total Porphyrins)
Porphobilinogen, Quantitative, 24-Hour Urine

CPT code 81050 may be added at an additional charge for volume measurement

4 mL of 24-hour urine containing sodium carbonate, collected in a plastic leak-proof container

2 mL

24-hour urine, collection should be adjusted to a pH of 6-7 with 5 g sodium carbonate (Na2CO3). Add the sodium carbonate at the start of the collection. The urine should be refrigerated and protected from light during collection.

Whenever possible, the specimen should be collected during an acute episode because porphobilinogen (PBG) may decrease rapidly upon remission. PBG may also degrade when samples are exposed to UV light for extended periods, or are transported at ambient temperature. If an amber collection jug/urine cup is not available, the sample must be protected from light by completely wrapping the container in aluminum foil. Twenty-four hour specimens should be refrigerated and protected from UV light during collection. PBG is most stable at pH 6-7, but samples may be sent with or without preservative. All results should be interpreted in the context of clinical findings, relevant history, and other laboratory data.

Refrigerated (cold packs)

Room temperature: Unacceptable
Refrigerated: 7 days
Frozen: 30 days

Not protected from light • pH <4.0 (acidified urine)

Set up: Sun, Tues-Fri; Report available: 5-7 days

Porphyrins, Fractionated, Quantitative, 24-Hour Urine

Uroporphyrin I	4.1-22.4 mcg/24 h
Uroporphyrin III	0.7-7.4 mcg/24 h
Heptacarboxyporphyrin	≤3.3 mcg/24 h
Hexacarboxyporphyrin	≤10 mcg/24 h
Pentacarboxyporphyrin	≤4.6 mcg/24 h
Coproporphyrin I	7.1-48.7 mcg/24 h
Coproporphyrin III	11.0-148.5 mcg/24 h
Total Porphyrins	35.0-210.7 mcg/24 h

Porphobilinogen, Quantitative, 24-Hour Urine

Pediatric	Not established
Adult	<0.34 mg/24 h

Urinary Porphobilinogen is the first step in the diagnosis of acute porphyrias such as acute intermittent porphyria (AIP). AIP is an autosomal dominant disorder characterized by deficiency of porphobilinogen deaminase. An acute attack usually includes gastrointestinal disturbance and neuropsychiatric disorders.