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|Methodology:||Inductively Coupled Plasma/Mass Spectroscopy (ICP/MS)|
|Performed:||Tuesday, Thursday, Saturday|
|Released:||1-4 days after setup at PeaceHealth Laboratories’ reference lab|
|Specimen Collection Details|
|Collection:||One 6 mL royal blue top trace-element serum tube. Also acceptable: One 6 mL royal blue top tube (EDTA) K2. Patient should be encouraged to discontinue nutritional supplements, vitamins, minerals, nonessential over-the-counter medications (upon the advice of their physician).|
|Handling:||Allow to clot, centrifuge and separate serum from cells and immediately pour into either an ARUP Trace Element-Free transport tube, available from PeaceHealth Laboratories Client Services, or a 6 mL royal blue trace element-no additive tube. Do not allow serum to remain on cells. Refrigerate.|
|Stability:||If the sample is drawn and stored in the appropriate container, the trace element values do not change with time.|
|Standard Volume:||2 mL serum or plasma.|
|Minimum Volume:||0.5 mL serum or plasma.|
|Comments:||Useful for monitoring selenium replacement therapy. Elevated results from noncertified trace element-free tubes may be due to contamination. Elevated concentrations of trace elements in serum should be confirmed with a second specimen collected in a trace element-free tube, such as royal blue sterile tube (no additive).|
|Rejection Criteria:||Tube other than specified; specimen not clotted or separated from cells; hemolysis.|
|Selenium is an essential element. It is a cofactor required to maintain glutathione peroxidase (GSH-Px) activity, and enzyme that catalyzes the degradation of organic hydroperoxides. The absence of selenium correlates with loss of GSH-Px activity and is associated with damage to cell membranes due to accumulation of free radicals. In humans, cardiac muscle is the most susceptible to selenium deficiency; with cell membrane damage, normal cells are replaced by fibroblasts. This condition is known as cardiomyopathy and is characterized by an enlarged heart whose muscle is largely replaced by fibrous tissue. In the United States, deficiency is related to use of total parenteral nutrition. This is therapy administered to patients with no functional bowel, such as after surgical removal of the small and large intestine because of cancer, or because of acute inflammatory bowel disease such as Crohn’s disease. Selenium supplementation to raise serum concentration above 90 ng/mL is the usual treatment; serum monitoring done on a semi-annual basis checks the adequacy of supplementation. Selenium toxicity has been observed in animals when daily intake exceeds 4 ppm. Teratogenic effects are frequently noted in the offspring of animals living in regions where soil content is high in selenium such as south central South Dakota and northern coastal regions of California. Selenium is not classified as a human teratogen. Selenium toxicity in humans is not known to be a significant problem except in acute overdose cases. Selenium is found in many over-the-counter vitamin preparations because its antioxidant activity is thought to be anticarcinogenic; there is no supporting evidence that selenium suppresses cancer.
Interpretation: the normal daily intake of selenium is 0.01-0.04 ppm, which is similar to the typical content of soil (0.05 ppm) and sea water (0.09 ppm). Selenium accumulates in biological tissue; the normal concentration in human blood serum is 95-160 ng/mL (0.15 ppm). In the state of selenium deficiency associated with loss of GSH-Px activity, the serum concentration is usually <40 ng/mL.