2 mL serum from a royal blue trace metal-free tube without
additive. Allow tube to clot for at least 60 minutes, then
centrifuge sample and separate serum from cells within
2 hours of collection. Transfer 2 mL serum to a plastic
transport tube. Clearly label tube as serum from a royal
blue top tube. Room temperature.

Diet, medication, and nutritional supplements may introduce
interfering substances. Patient should be encouraged to
discontinue nutritional supplements, vitamins, minerals,
and non-essential over-the-counter medications (upon the
advice of their physician).