Selenium
Selenium is an essential element that is a cofactor for glutathione peroxidase (GSH-Px). The normal daily dietary intake of selenium is 0.01 to 0.04 parts per million (ppm), which is similar to the typical content of soil (0.05 ppm) and sea water (0.09 ppm). Selenium is included in many over-the-counter vitamins because its antioxidant activity has been rumored to prevent cancer.
Selenium deficiency leads to decreased GSH-Px activity, which is associated with cell membrane damage by free radicals. The most serious complication of selenium deficiency is cardiomyopathy due to myocardial cell death and replacement by fibrous tissue.
In the United States, the most common cause of selenium deficiency is use of total parenteral nutrition. Patients are treated with selenium supplements to maintain the serum concentration above 70 ng/mL.
Selenium is measured by inductively coupled plasma mass spectrometry (ICP-MS). Reference range for blood levels of selenium in adults is 150-240 ng/mL.
Specimen is whole blood collected into a royal blue-top (EDTA) Vacutainer tube, which is free of trace elements. 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.
