Metanephrines

Metanephrines

Synonym/acronym: N/A.

Common use

To assist in the diagnosis of cancer of the adrenal medulla or to assess for the cause of hypertension.

Specimen

Urine (25 mL) from a timed specimen collected in a clean amber plastic collection container with 6N hydrochloride as a preservative.

Normal findings

(Method: High-pressure liquid chromatography)
AgeConventional UnitsSI Units
Normetanephrines (Conventional Units × 5.07)
3 mo–4 yr54–249 mcg/24 hr274–1,262 micromol/day
5–9 yr31–398 mcg/24 hr157–2,018 micromol/day
10–17 yr67–531 mcg/24 hr340–2,692 micromol/day
18–39 yr35–482 mcg/24 hr177–2,444 micromol/day
Greater than 40 yr88–676 mcg/24 hr446–3,427 micromol/day
Metanephrines, Total (Conventional Units × 5.07)
3 mo–4 yr79–345 mcg/24 hr401–1,749 micromol/day
5–9 yr49–409 mcg/24 hr248–2,074 micromol/day
10–17 yr107–741 mcg/24 hr543–3,757 micromol/day
18–39 yr94–695 mcg/24 hr477–3,524 micromol/day
40–49 yr182–739 mcg/24 hr923–3,747 micromol/day
Greater than 50 yr224–832 mcg/24 hr1,136–4,218 micromol/day

Description

Metanephrines are the inactive metabolites of epinephrine and norepinephrine. Metanephrines are either excreted or further metabolized into vanillylmandelic acid. Release of metanephrines in the urine is indicative of disorders associated with excessive catecholamine production, particularly pheochromocytoma. Vanillylmandelic acid and catecholamines are normally measured with urinary metanephrines. Creatinine is usually measured simultaneously to ensure adequate collection and to calculate an excretion ratio of metabolite to creatinine.

This procedure is contraindicated for

    N/A

Indications

  • Assist in the diagnosis of suspected pheochromocytoma
  • Assist in identifying the cause of hypertension
  • Verify suspected tumors associated with excessive catecholamine secretion

Potential diagnosis

Increased in

  • Ganglioneuroma
  • Neuroblastoma
  • Pheochromocytoma
  • Severe stress

Decreased in

    N/A

Critical findings

    N/A

Interfering factors

  • Drugs that may increase metanephrine levels include monoamine oxidase inhibitors and prochlorperazine.
  • Methylglucamine in x-ray contrast medium may cause false-negative results.
  • All urine voided for the timed collection period must be included in the collection or else falsely decreased values may be obtained. Compare output records with volume collected to verify that all voids were included in the collection.

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 diagnosing adrenal gland health and hypertension.
  • 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 endocrine system, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Note any recent procedures that can interfere with test results.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
  • 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.
  • At the conclusion of the test, compare the 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, thus invalidating the test.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Instruct the patient to avoid excessive exercise and stress during the 24-hr collection of urine.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.

Intratest

  • Potential complications: N/A
  • Ensure that the patient has complied with activity restrictions during the procedure.
  • 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.
  • 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, compare the 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 and test start and stop times.
  • 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.
  • Instruct the patient to resume usual activity, as directed by the HCP.
  • Recognize anxiety related to test results, and be supportive of fear of shortened life expectancy. 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.
  • 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 angiography adrenal, cancer antigens, catecholamines, CT renal, HVA, renin, and VMA.
  • Refer to the Endocrine System table at the end of the book for related tests by body system.
References in periodicals archive ?
Evaluation includes biochemical diagnosis with elevated plasma or urine catecholamines and metanephrines (plasma metanephrines are preferred).
Urinary fractionated metanephrines and peer-based laboratory proficiency testing [Letter].
PCC is diagnosed by measurements of catecholamines and metanephrines in the serum and in a 24-hour urine collection, with a 98% sensitivity and specificity.
10] Clinically, patients present with paroxysmal hypertension, palpitations, flushing, diaphoresis and elevated levels of cathecholamines, vanillylmandelic acid and metanephrines.
A metabolic workup typically includes serum electrolytes, cortisol, adrenocorticotropic hormone, aldosterone, renin, urinary catecholamines, metanephrines, vanillylmandelic acid, 17-ketosteroids, and 17-hydroxycorticoids.
The patient's 24-hour urine metanephrines were markedly elevated at 4057 mcg (reference range, 0-899), with normetanephrines of 4015 mcg (reference range, 0-599) and a metanephrine-to-creatinine ratio of 2352 (reference range, 0-599).
If suspected, a detailed family history should be obtained and measurement of plasma or urinary metanephrines or catecholamines performed.
The postoperative urinary metanephrines and MIBG scan were normal.
Systemic systolic hypertension in the elderly: correlation of hemodynamics, plasma volume, renin, aldosterone, urinary metanephrines and response to thiazide therapy.
Figure 4 shows a 48-yearold man with elevated catecholamines and metanephrines with uncontrolled hypertension.
The simplest and most reliable test for evaluating pheochromocytoma is measurement of plasma free metanephrines rather than traditional testing by quantitating urinary vanillylmandelic acid or catecholamines.
Biochemical evaluation should include a 24-hour urine collection for norepinephrine, epinephrine, metanephrines, normetanephrines, dopamine, and VMA, or plasma metanephrines and normetanephrines, which is expensive, but more sensitive, especially in patients who may harbor occult diagnoses of familial syndromes, such as multiple endocrine neoplasia Type 2, Von Hippel Lindau or familial paragangliomas.