Porphyrins, Urine

Synonym/acronym: Coproporphyrin, porphobilinogen, urobilinogen, and other porphyrins.

Common use

To assess for porphyrias in the urine to assist with diagnosis of genetic disorders associated with porphyrin synthesis as well as heavy metal toxicity.

Specimen

Urine (10 mL) from a random or timed specimen collected in a clean, amber-colored plastic collection container with sodium carbonate as a preservative.

Normal findings

(Method: High-performance liquid chromatography for porphyrins; spectrophotometry for δ-aminolevulinic acid and porphobilinogen)

Test	Conventional Units	SI Units
		(Conventional Units × 1.53)
Coproporphyrin I	0–24 mcg/24 h	0–36.7 nmol/24 hr
Coproporphyrin III	0–74 mcg/24 hr	0–113.2 nmol/24 hr
		(Conventional Units × 1.43)
Uroporphyrins	0–24 mcg/24 hr	0–34.3 nmol/24 hr
		(Conventional Units × 1.34)
Hexacarboxylporphyrin	Less than 1 mcg/24 hr	Less than 1.34 nmol/24 hr
		(Conventional Units × 1.27)
Heptacarboxylporphyrin	Less than 4 mcg/24 hr	Less than 5.1 nmol/24 hr
		(Conventional Units × 4.42)
Porphobilinogen	Less than 2 mg/24 hr	Less than 8.8 micromol/24 hr
		(Conventional Units × 7.626)
δ-Aminolevulinic acid	1.5–7.5 mg/24 hr	11.4–57.2 micromol/24 hr

Description

Porphyrins are produced during the synthesis of heme. If heme synthesis is disturbed, these precursors accumulate and are excreted in the urine in excessive amounts. Conditions producing increased levels of heme precursors are called porphyrias. The two main categories of genetically determined porphyrias are erythropoietic porphyrias, in which major abnormalities occur in red blood cell chemistry, and hepatic porphyrias, in which heme precursors are found in urine and feces. Erythropoietic and hepatic porphyrias are rare. Acquired porphyrias are characterized by greater accumulation of precursors in urine and feces than in red blood cells. Lead poisoning is the most common cause of acquired porphyrias. Porphyrins are reddish fluorescent compounds. Depending on the type of porphyrin present, the urine may be reddish, resembling port wine. Porphobilinogen is excreted as a colorless compound. A color change may occur in an acidic sample containing porphobilinogen if the sample is exposed to air for several hours.

This procedure is contraindicated for

N/A

Indications

Assist in the diagnosis of congenital or acquired porphyrias characterized by abdominal pain, tachycardia, emesis, fever, leukocytosis, and neurological abnormalities
Detect suspected lead poisoning, as indicated by elevated porphyrins

Potential diagnosis

Increased in

Accumulation of porphyrins or porphyrin precursors in the body is common to the various types of porphyrias. Excessive amounts of circulating porphyrins and precursors are excreted in the urine.
Acute intermittent porphyria (related to an autosomal dominant disorder resulting in a deficiency of the enzyme porphobilinogen deaminase and increased excretion of porphobilinogen and delta-aminolevulinic acid [δ-ALA] in the urine)
Acquired or chemical porphyrias (heavy metal, benzene, or carbon tetrachloride toxicity; drug induced) (related to a disturbance in the heme biosynthetic pathway and increased excretion of delta-aminolevulinic acid in the urine)
ALAD deficiency porphyria (related to an autosomal recessive disorder resulting in a deficiency of the enzyme delta-aminolevulinic acid dehydratase and increased excretion of δ-ALA in the urine)
Hepatoerythropoietic porphyria (related to an autosomal recessive disorder resulting in a deficiency of the enzyme uroporphyrinogen decarboxylase and increased excretion of uroporphyrin and heptacarboxylporphyrin in the urine)
Hereditary coproporphyria (related to an autosomal dominant disorder resulting in a deficiency of the enzyme coproporphyrinogen oxidase and increased excretion of porphobilinogen, δ-ALA, and coproporphyrin in the urine)
Porphyria cutanea tarda (related to an acquired deficiency of the enzyme uroporphyrinogen decarboxylase activated by exposure to triggers such as iron, alcohol, hepatitis C virus, HIV, or estrogens and increased excretion of uroporphyrin, heptacarboxylporphyrin, and coproporphyrin in the urine)
Variegate porphyrias (related to an autosomal dominant disorder resulting in a deficiency of the enzyme protoporphyrinogen oxidase and increased excretion of porphobilinogen, coproporphyrin, and δ-ALA in the urine during attacks; excretion of normal levels may be found between attacks)

Decreased in

N/A

Critical findings

N/A

Interfering factors

Drugs that may increase urine porphyrin levels include acriflavine, aminopyrine, ethoxazene, griseofulvin, hexachlorobenzene, oxytetracycline, and sulfonmethane.
Numerous drugs are suspected as potential initiators of acute attacks, but drugs classified as unsafe for high-risk individuals include aminopyrine, aminoglutethimide, antipyrine, barbiturates, N-butylscopolammonium bromide, carbamazepine, carbromal, chlorpropamide, danazol, dapsone, diclofenac, diphenylhydantoin, ergot preparations, ethchlorvynol, ethinamate, glutethimide, griseofulvin, N-isopropyl meprobamate, mephenytoin, meprobamate, methyprylon, novobiocin, phenylbutazone, primidone, pyrazolone preparations, succinimides, sulfonamide antibiotics, sulfonethylmethane, sulfonmethane, synthetic estrogens and progestins, tolazamide, tolbutamide, trimethadione, and valproic acid.
Exposure of the specimen to light can falsely decrease values.
Screening methods are not well standardized and can produce false-negative results.
Failure to collect all urine and store specimen properly during the 24-hour test period will interfere with results.

Nursing Implications and Procedure

Pretest

Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
Patient Teaching: Inform the patient this test can assist in evaluating for conditions producing increased levels of heme precursors called porphyrias.
Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
Obtain a history of the patient’s hematopoietic system, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values).
Review the procedure with the patient. Provide a nonmetallic urinal, bedpan, or toilet-mounted collection device. Address concerns about pain and explain that there should be no discomfort during the procedure.
Usually a 24-hr time frame for urine collection is ordered. Inform the patient that all urine must be saved during that 24-hr period. Instruct the patient not to void directly into the laboratory collection container. Instruct the patient to avoid defecating in the collection device and to keep toilet tissue out of the collection device to prevent contamination of the specimen. Place a sign in the bathroom to remind the patient to save all urine.
Instruct the patient to void all urine into the collection device and then to pour the urine into the laboratory collection container. Alternatively, the specimen can be left in the collection device for a health-care staff member to add to the laboratory collection container.
Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
Note that there are no food, fluid, or medication restrictions unless by medical direction.

Intratest

Potential complications: N/A
Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
Instruct the patient to cooperate fully and to follow directions.
Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection.

Random Specimen (Collect in Early Morning)

Clean-Catch Specimen
Instruct the male patient to (1) thoroughly wash his hands, (2) cleanse the meatus, (3) void a small amount into the toilet, and (4) void directly into the specimen container.
Instruct the female patient to (1) thoroughly wash her hands; (2) cleanse the labia from front to back; (3) while keeping the labia separated, void a small amount into the toilet; and (4) without interrupting the urine stream, void directly into the specimen container.

Indwelling Catheter

Put on gloves. Empty drainage tube of urine. It may be necessary to clamp off the catheter for 15 to 30 minutes before specimen collection. Cleanse specimen port with antiseptic swab, and then aspirate 5 mL of urine with a 21- to 25-gauge needle and syringe. Transfer urine to a sterile container.

Timed Specimen

Obtain a clean 3-L urine specimen container, toilet-mounted collection device, and plastic bag (for transport of the specimen container). The specimen must be refrigerated or kept on ice throughout the entire collection period. If an indwelling urinary catheter is in place, the drainage bag must be kept on ice.
Begin the test between 6 and 8 a.m. if possible. Collect first voiding and discard. Record the time the specimen was discarded as the beginning of the timed collection period. The next morning, ask the patient to void at the same time the collection was started and add this last voiding to the container. Urinary output should be recorded throughout the collection time.
If an indwelling catheter is in place, replace the tubing and container system at the start of the collection time. Keep the container system on ice during the collection period, or empty the urine into a larger container periodically during the collection period; monitor to ensure continued drainage, and conclude the test the next morning at the same hour the collection was begun.
At the conclusion of the test, comparethe quantity of urine with the urinary output record for the collection; if the specimen contains less than what was recorded as output, some urine may have been discarded, invalidating the test.
Include on the collection container’s label the amount of urine, test start and stop times, and ingestion of any foods or medications that can affect test results.

General

Promptly transport the specimen to the laboratory for processing and analysis.

Post-Test

Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
Nutritional Considerations: Increased δ-ALA levels may be associated with an acute porphyria attack. Patients prone to attacks should eat a normal or high-carbohydrate diet. Dietary recommendations may be indicated and will vary depending on the condition and its severity; however, restrictions of or wide variations in dietary carbohydrate content should be avoided, even for short periods of time. After recovering from an attack, daily intake of carbohydrates should be 300 grams or more per day.
Recognize anxiety related to test results. Discuss the implications of abnormal test results on the patient’s lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate. Educate the patient regarding access to counseling services. Provide contact information, if desired, for the American Porphyria Foundation (www.porphyriafoundation.com).
Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

Related tests include δ-aminolevulinic acid, erythrocyte protoporphyrin, and lead.
Refer to the Hematopoietic System table at the end of the book for related tests by body system.