Serum-separating tube
Serum-separating tubes, also known as serum separator tubes or SSTs, are used in medical clinical chemistry tests requiring blood serum.
SSTs are sometimes called "marble-top tubes," "target-tops," or "gold-topped tubes", referring to the stoppers which are either gold, red with a gold ring on top, or marbled red and grey. Marble-top tubes are also referred to as "tiger-tops" in some clinics. SPS tubes have a paler colour, sometimes leading confusion, these are known as "Yellow tops" not "Gold". Trademarked versions include Covidien "Corvac" tubes.
They contain a special gel that separates blood cells from serum, as well as particles to cause blood to clot quickly. The blood sample may then be centrifuged, allowing the clear serum to be removed for testing.[1]
These tubes should be used with care when measuring therapeutic drug levels because the drug/hormone may diffuse from the serum into the gel, causing a reduction in measured drug level. The gel in SST II tubes (which appears slightly less opaque) is supposed to have less effect on drug levels in serum.
References
- ↑ Blood sampling in sheep (170kb pdf) from Purdue University, 2003.