To measure the amount of selenium in the blood (serum/plasma) in order to identify/diagnose deficiency/toxicity or to monitor the response to supplementation
A blood sample taken from a vein in your arm.
This test measures the amount of selenium in the serum/plasma. Selenium is an essential trace element with important functions throughout the body. Selenium has several important roles including the synthesis and metabolism of thyroid hormones, immune function and in antioxidative processes.
Selenium is found in many foods but has highest quantities in brazil nuts, seafood, kidney and meat.
The selenium content of rice and cereals varies depending upon the geographical region as some soils are high in selenium (USA) whereas others have low levels (New Zealand). Selenium is well absorbed from the gastrointestinal tract and homeostasis is achieved by excretion in the urine.
If selenium deficiency is severe it can present clinically with muscle weakness, dizziness, nausea and cardiomyopathy. Toxicity may also occur following over-ingestion of supplements/foods or through occupational exposure e.g manufacturing processes such as ceramics, glass and semiconductors. Symptoms of toxicity include irritation to eyes and mucus membranes, altered consciousness and cardio-respiratory arrest.
How is the sample collected for testing?
A blood sample is taken from a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
How is it used?
When is it requested?
When a person has suspected selenium deficiency or toxicity. In particular selenium is measured in individuals receiving supplements, especially those who are receiving total parenteral nutrition (TPN) which is supplemented via the non-oral route.
What does the test result mean?
Serum/plasma selenium concentrations can decrease during the acute phase response to illness or trauma. This does not necessarily infer selenium deficiency but may be a response to a redistribution of selenium (into tissues). Functional selenium deficiency can be assessed by measurement of the enzyme activity of selenium-dependent proteins e.g glutathione peroxidase. Serum/plasma selenium concentrations correspond to recent selenium intake whereas the measurement of whole blood selenium or glutathione peroxidase activity correlates with longer-term selenium status.
Is there anything else I should know?
Low selenium intake and deficiency has been associated with increased risk of cancer and cardiomyopathy. Supplementation may improve brain function in particular it is thought to improve mood, depression, anxiety and confusion.
Should I take selenium supplements?
Most individuals have an adequate supply of selenium in their diet and supplementation is not necessary. However, if you have any concerns please consult your GP who can review your dietary intake, investigate any symptoms and advise if testing is required.
When is it recommended to measure glutathione peroxidase activity?
If a person has a low serum/plasma selenium this may suggest the possibility of selenium deficiency. Glutathione peroxidase activity is a measure of functional selenium deficiency since low selenium concentrations do not necessarily mean a person is selenium deficient.