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Test ID: ASFRU Arsenic Fractionation, Random, Urine

Reporting Name

Arsenic Fractionation, Random, U

Useful For

Diagnosis of arsenic intoxication in random urine specimens

Clinical Information

Arsenic (As) exists in a number of different forms; some are toxic, while others are not. The toxic forms are the inorganic species of As(+3) (As-III), As(+5) (As-V), and their partially detoxified metabolites, monomethylarsine, and dimethylarsine. As-III is more toxic than As-V and both are more toxic than mono- and dimethylarsine. The biologic half-life of inorganic arsenic is 4 to 6 hours, while the biologic half-life of the methylated metabolites is 20 to 30 hours. Target organs of As-III-induced effects are the heart, gastrointestinal tract, skin and other epithelial tissues, kidney, and nervous system.

 

Inorganic arsenic is carcinogenic to humans. Symptoms of chronic poisoning, 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.

 

Nontoxic, organic forms of arsenic are present in many foods. Arsenobetaine and arsenocholine are the 2 most common forms of organic arsenic found in food. The most common foods that contain significant concentrations of organic arsenic are shellfish and other predators in the seafood chain (cod, haddock, etc). Some meats, such as from chickens that have been fed on seafood remnants, may also contain the organic forms of arsenic.

 

Following ingestion of arsenobetaine and arsenocholine, these compounds undergo rapid renal clearance to become concentrated in the urine. Organic arsenic is completely excreted within 1 to 2 days after ingestion and there are no residual toxic metabolites. The biologic half-life of organic arsenic is 4 to 6 hours.

 

For reporting purposes, the concentrations of the inorganic forms (As[+3] and As[+5]) along with the methylated forms (monomethylarsine and dimethylarsine) will be summed and reported together as 'Inorganic' arsenic. This is consistent with how the biological exposure index (BEI) reference range is reported.

Interpretation

The quantitative reference range for fractionated arsenic applies only to the inorganic forms. Concentrations of 20 mcg inorganic arsenic per liter or higher are considered toxic.

 

There is no limit to the normal range for the organic forms of arsenic, since they are not toxic and are normally present after consumption of certain food types. For example, a typical finding in a urine specimen with total 24-hour excretion of arsenic of 350 mcg/24 hours would be that more than 95% is present as the organic species from a dietary source, and less than 5% is present as the inorganic species. This would be interpreted as indicating the elevated total arsenic was due to ingestion of the nontoxic form of arsenic, usually found in food.

 

A normal value for blood arsenic does not exclude a finding of elevated urine inorganic arsenic, due to the very short half-life of blood arsenic.

Testing Algorithm

Total arsenic will be performed first. If the total arsenic concentration is 15 mcg/L or greater, then fractionation will be performed and reported.  If total arsenic is below 15 mcg/L, total arsenic will be reported as less than 15 mcg/L and fractionation will not be performed.

Analytic Time

2 days

Day(s) and Time(s) Performed

Monday through Friday; 8 a.m.

Clinical Reference

Caldwell KL, Jones RL, Verdon CP, et al: Levels of urinary total and speciated arsenic in the US population: National Health and Nutrition Examination Survey 2003-2004. J Expo Sci Environ Epidemiol 2009;19:59-68

Method Name

Ion Chromatography Extraction/Inductively Coupled Plasma-Mass Spectrometry (IC-ICP-MS)

Specimen Type

Urine


Specimen Required


Patient Preparation:

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

2. 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.

Supplies:

Urine Tubes, 10 mL (T068)

Aliquot Tube, 5 mL (T465)

Collection Container/Tube: Clean, plastic urine collection container

Submission Container/Tube: Plastic, 5-mL tube (T465) or a clean, plastic aliquot container with no metal cap or glued insert

Specimen Volume: 5 mL

Collection Instructions:

1. Collect a random urine specimen.

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


Specimen Minimum Volume

3 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Urine Refrigerated (preferred) 28 days
  Frozen  28 days
  Ambient  72 hours

Reference Values

TOTAL ARSENIC

<20 mcg/L

 

INORGANIC ARSENIC

<20 mcg/ L

 

Reference values apply to all ages.

 

*Biological exposure indices (BEI) for arsenic is 35 mcg/L based on the concentration of inorganic arsenic plus methylated metabolites.

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.

CPT Code Information

82175

LOINC Code Information

Test ID Test Order Name Order LOINC Value
ASFRU Arsenic Fractionation, Random, U 54454-4

 

Result ID Test Result Name Result LOINC Value
32311 Inorganic Arsenic (Toxic) 12481-8
32312 Organic Arsenic (Non-Toxic) 53778-7
113134 Total Arsenic 5586-3
Mayo Clinic Laboratories | Neurology Catalog Additional Information:

mml-Behavioral, mml-Neuromuscular