1 mL serum from a royal blue trace metal-free tube without additive. Centrifuge sample and separate serum from cells within 2 hours of collection. Transfer serum to a plastic transport tube. Clearly label tube as serum from a royal blue top tube. Refrigerate.
Diet, medication, and nutritional supplements may introduce interfering substances. Patients should be encouraged to discontinue nutritional supplements, vitamins, minerals and non-essential over-the-counter medications (upon the advice of their physician) for 1 week prior to collection. Avoid exposure to contrast media for 96 hours prior to collection.