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Test Code ASU Arsenic, 24 Hour, Urine

Reporting Name

Arsenic, 24 Hr, U

Useful For

Preferred screening test for detection of arsenic exposure

Method Name

Inductively Coupled Plasma-Mass Spectrometry (ICP-MS)

Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type

Urine

Specimen Required

Collection Container/Tube: Clean, plastic urine container with no metal cap or glued insert

Submission Container/Tube: Plastic, 10-mL urine tube (Supply T068) or clean, plastic aliquot container with no metal cap or glued insert

Specimen Volume: 10 mL
Collection Instructions:

1. Collect urine for 24 hours.

2. Refrigerate specimen within 4 hours of completion of 24-hour collection.

3. Patient should not eat seafood for a 48-hour period prior to start of collection.

4. See Trace Metals Analysis Specimen Collection and Transport in Special Instructions for complete instructions.

Additional Information:

1. 24-Hour volume is required.

2. See Urine Preservatives in Special Instructions for multiple collections.

3. High concentrations of gadolinium and iodine are known to interfere with most metals tests. If either gadolinium- or iodine-containing contrast media has been administered, a specimen should not be collected for 96 hours.

 

Urine Preservative Collection Options

Ambient

Yes

Refrigerated

Preferred

Frozen

Yes

6N HCl

Yes

50% Acetic Acid

Yes

Na2CO3

No

Toluene

Yes

6N HNO3

No

Boric Acid

No

Thymol

No

Specimen Minimum Volume

2 mL

Specimen Stability Information

Specimen Type Temperature Time
Urine Refrigerated (preferred) 28 days
  Ambient  28 days
  Frozen  28 days

Reject Due To

Hemolysis

NA

Lipemia

NA

Icterus

NA

Other

NA

Reference Values

0-35 mcg/specimen

Reference values apply to all ages.

Day(s) and Time(s) Performed

Monday through Friday; 3 p.m.–9 p.m., Saturday; 8 a.m.–3 p.m.; Continuously

CPT Code Information

82175

LOINC Code Information

Result ID Reporting Name LOINC Code
31086 Arsenic, 24 Hr, U 5587-1
TIME3 Collection Duration 13362-9
VL14 Urine Volume 3167-4
859 As Concentration 21074-0

Clinical Information

Arsenic is perhaps the best known of the metal toxins, having gained notoriety from its extensive use by Renaissance nobility as an antisyphilitic agent and, paradoxically, as an antidote against acute arsenic poisoning. Even today, arsenic is still 1 of the more common toxicants found in insecticides, and leaching from bedrock to contaminate groundwater.

 

The toxicity of arsenic is due to 3 different mechanisms, 2 of them related to energy transfer. Arsenic covalently and avidly binds to dihydrolipoic acid, a necessary cofactor for pyruvate dehydrogenase. Absence of the cofactor inhibits the conversion of pyruvate to acetyl coenzyme A, the first step in gluconeogenesis. This results in loss of energy supply to anaerobic cells, the predominant mechanism of action of arsenic on neural cells that rely on anaerobic respiration for energy. Neuron cell destruction that occurs after long-term energy loss results in bilateral peripheral neuropathy.

 

Arsenic also competes with phosphate for binding to adenosine triphosphate during its synthesis by mitochondria via oxidative phosphorylation, causing formation of the lower energy adenosine diphosphate monoarsine. This results in loss of energy supply to aerobic cells. Cardiac cells are particularly sensitive to this form of energy loss; fatigue due to poor cardiac output is a common symptom of arsenic exposure.

 

Arsenic furthermore binds avidly with any hydrated sulfhydryl group on protein, distorting the 3-dimensional configuration of that protein, causing it to lose activity. Interaction of arsenic with epithelial cell protein at the sites of highest physiologic concentration, the small intestine and proximal tubule of the kidney, results in cellular degeneration. Epithelial cell erosion in the gastrointestinal tract and proximal tubule are characteristic of arsenic toxicity. Arsenic is also a known carcinogen, but the mechanism of this effect is not definitively known.

 

A wide range of signs and symptoms may be seen in acute arsenic poisoning including headache, nausea, vomiting, diarrhea, abdominal pain, hypotension, fever, hemolysis, seizures, and mental status changes. Symptoms of chronic poisoning, also called arseniasis, are mostly insidious and nonspecific. The gastrointestinal tract, skin, and central nervous system are usually involved. Nausea, epigastric pain, colic abdominal pain, diarrhea, and paresthesias of the hands and feet can occur.

 

Arsenic exists in a number of different forms; organic forms are nontoxic, inorganic forms are toxic. See ASFR / Arsenic Fractionation, 24 Hour, Urine for details about arsenic forms.

 

Because arsenic is excreted predominantly by glomerular filtration, analysis for arsenic in urine is the best screening test to detect arsenic exposure.

Interpretation

Normally, humans consume 5 to 25 mcg of arsenic each day as part of their normal diet; therefore, normal urine arsenic output is <25 mcg/specimen. After a seafood meal (seafood contains a nontoxic, organic form of arsenic), the urine output of arsenic may increase to 300 mcg/specimen for 1 day, after which it will decline to <25 mcg/specimen.

 

Exposure to inorganic arsenic, the toxic form of arsenic, causes prolonged excretion of arsenic in the urine for many days.

 

Urine excretion rates >1,000 mcg/specimen indicate significant exposure. The highest level observed at Mayo Clinic was 450,000 mcg/specimen in a patient with severe symptoms of gastrointestinal distress, shallow breathing with classic "garlic breath," intermittent seizure activity, cardiac arrhythmias, and later onset of peripheral neuropathy.

Cautions

Consumption of seafood before collection of a urine specimen for arsenic testing is likely to result in a report of an elevated concentration of arsenic found in the urine, which can be clinically misleading.

 

High concentrations of gadolinium and iodine are known to interfere with most metals tests. If either gadolinium- or iodine-containing contrast media has been administered, a specimen should not be collected for 96 hours.

Method Description

This assay is performed on an inductively coupled plasma-mass spectrometer. Calibrating standards and blanks are diluted with an aqueous acidic diluent containing internal standard(s). Quality control specimens and patient samples are diluted in an identical manner. In turn, all diluted blanks, calibrating standards, quality control specimens, and patient specimens are aspirated into a pneumatic nebulizer and the resulting aerosol directed to the hot plasma discharge by a flow of argon. In the annular plasma the aerosol is vaporized, atomized, then ionized. The ionized gases plus neutral species formed in the annular plasma space are aspirated from the plasma through an orifice into a quadrapole mass spectrometer. The mass range from 1 to 263 amu is rapidly scanned multiple times and ion counts tabulated for each mass of interest. Instrument response is defined by the linear relationship of analyte concentration vs. ion count ratio (analyte ion count/internal standard ion count). Analyte concentrations are derived by reading the ion count ratio for each mass of interest and determining the concentration from the response line.(Nixon DE, Moyer TP: Routine clinical determination of lead, arsenic, cadmium, and thallium in urine and whole blood by inductively coupled plasma mass spectrometry. Spectrochimica Acta B 1996;51:13-25)

Analytic Time

1 day

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.