Porphyrins, Quantitative, 24 Hr Urine (PQNU)

Test Code: PORPHU

Overview
Ordering
Specimen
Performing
Clinical/Interpretive
Contacts
Coding

Synonyms/Keywords

Ref Lab Code: 8562, Acute Intermittent Porphyria (AIP), Congenital Erythropoietic Porphyria (CEP), Coproporphyrin,
Heptacarboxyl Porphyrin, Hereditary Coproporphyria (HCP), Hexacarboxyl Porphyrin, PBG (Porphobilinogen),
Pentacarboxyl Porphyrin, Porphobilinogen (PBG), Porphyria Cutanea Tarda (PCT), Porphyrins, Fractionation, Urine Uroporphyrin, Variegate Porphyria (VP)

Useful For

Preferred screening test during symptomatic periods for acute intermittent porphyria, hereditary coproporphyria, and variegate porphyria (additional confirmatory testing is required to establish a diagnosis)

Preferred screening test to begin assessment for congenital erythropoietic porphyria and porphyria cutanea tarda (additional confirmatory testing is required to establish a diagnosis)

Specimen Requirements

Specimen Type	Preferred Container/Tube	Acceptable Container/Tube	Specimen Volume	Specimen Minimum Volume (allows for 1 repeat)	Pediatric Minimum Volume (no repeat)
Urine	Amber, 60 mL urine bottle (24 hour urine container)		20-50 mL	15 mL

Collection Processing Instructions

1. Patient should abstain from alcohol for 24 hours prior to, as well as during, collection.

2. Collect a 24-hour urine specimen.

3. Add 5 g of sodium carbonate as preservative at start of collection. This preservative is intended to achieve a pH of >7. Do not substitute sodium bicarbonate for sodium carbonate.

4. The container should be refrigerated and protected from light as much as possible during collection.

5. Protect specimen from light.

Additional Information:

1. 24-Hour volume is required.

2. Collection date and time should be documented upon completion of the 24-hour collection.

3. Include a list of medications the patient is currently taking.

4. The pH will generally fall between 7 and 10 if the proper preservative (5 g sodium carbonate) was added to the container before the collection was started.

5. See Urine Preservatives in Special Instructions for multiple collections.
Urine Preservative Cross-Reference Information

Specimen Stability Information

Specimen Type	Temperature	Time
Urine	Frozen	7 days

Rejection Criteria

Specimen not protected from light, pH <5.0

Performing Laboratory Information

Performing Location	Day(s) Test Performed	Analytical Time	Methodology/Instrumentation
Mayo Medical Laboratories	Monday through Friday	2 days (not reported on Saturday or Sunday)	High-Performance Liquid Chromatography (HPLC) with Fluorometric Detection Includes quantitation of coproporphyrins, uroporphyrins, and intermediate porphyrins (heptacarboxyl, hexacarboxyl, and pentacarboxyl). Includes liquid chromatography-tandem mass spectrometry (LC-MS/MS) determination of porphobilinogen.

Reference Lab

Mayo Clinic Laboratories

Test Information

The measurement of PBG in urine is important in the diagnosis of acute, neurologic porphyrias including acute intermittent porphyria (AIP), hereditary coproporphyria (HCP), and variegate porphyria (VP). Urinary porphyrin determination is helpful in the diagnosis of these disorders, as well as other porphyrias including congenital erythropoietic porphyria (CEP) and porphyria cutanea tarda (PCT).

Reference Range Information

UROPORPHYRINS (octacarboxyl)

< or =30 nmol/24 hours

HEPTACARBOXYLPORPHYRINS

< or =9 nmol/24 hours

HEXACARBOXYLPORPHYRINS

< or =8 nmol/24 hours

PENTACARBOXYLPORPHYRINS

< or =10 nmol/24 hours

COPROPORPHYRINS (tetracarboxyl)

Males: < or =230 nmol/24 hours

Females: < or =168 nmol/24 hours

PORPHOBILINOGEN

< or =2.2 mcmol/24 hours

Outreach CPTs

CPT	Modifier (if needed)	Quantity	Description	Comments
84110			Porphobilinogen, urine, quantitation
84120			Porphyrin, urine, quantation and fractionation