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 ?
Biochemical assay includes elevated plasma fractionated metanephrines or elevated 24-h urinary fractionated metanephrines10.
According to the North American Neuroendocrine Tumor Society guidelines, the initial testing for pheochromocytoma or paraganglioma must include measurements of fractionated metanephrines in plasma, urine, or both, as available.
Measurement of plasma free metanephrine and normetanephrine or 24-h urinary fractionated metanephrines are considered to be the most accurate biochemical tests for pheochromocytoma (4).
Representation of the analytical alterations Patient values Potassium 3.19 mmol/L [down arrow] Aldosterone 21.9 ng/mL [up arrow] Active renin 0.8 uU/mL [down arrow] Aldosterone/active renin index 27.4 ng/mL/h [up arrow] Vanilmandelic acid (Urinary) 7.46 mg/24h [up arrow] Metanephrines and 114 mcg/24h [down arrow] normetanephrines (Urinary) 141 mcg/24h [down arrow] Reference values Potassium 3.5-5-1 mmol/L Aldosterone > 20 ng/mL Active renin 7-76 uU/mL Aldosterone/active renin index > 25 ng/mL/h Vanilmandelic acid (Urinary) 2.0-7.0 mg/24h Metanephrines and <350 mcg/24h normetanephrines (Urinary) <600 mcg/24h
Pre-operative diagnostic tests include 24-hour urine or plasma fractionated catecholamines and metanephrines. However, these tests may be normal in certain tumours that only produce small levels of catecholamines or exclusively secrete dopamine.
A minimum 6-point calibration range covering the therapeutic range for the measurement of plasma catecholamines and metanephrines.
Serum aldosterone, dexamethasone suppression test, dehydroepiandrosterone sulfate, and 24-hour urine metanephrines were within normal limits.
As such, testing for catecholamine and metanephrines is recommended in symptomatic patients [29, 33].
Laboratory results, including cancer biological markers, liver function and renal tests, and serum hormone profile (cortisol, aldosterone, calcium, urinary catecholamines, 5-HIAA, and metanephrines), were within normal limits.
We measured plasma metanephrines in EDTA plasma by LC-MS/MS (28) and urine metanephrines by HPLC with electrochemical detection (Chromsystems).
Serum CgA can be used as a screening or monitoring test for NET in combination with the specific metabolic test for that particular NET (e.g., plasma fractionated metanephrines for pheochromocytoma, plasma 5-hydroxyindoleacetic acid for carcinoid, plasma gastrin for gastrinomas, plasma glucagon for glucagonomas) and necessary radiological investigation(s), all of which will help to diagnose the burden and progress of the tumor.