Serum-separating tube
{{Short description|Test tubes used with blood}}
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A serum-separating tube or serum separator tube (SST) is a test tube used in clinical chemistry tests requiring blood serum.
SSTs are sometimes called "gold-topped tubes", "tiger-tops", or "marble-top tubes", referring to the colored stoppers which are either gold, red with a gold ring on top, or marbled red and grey. Stoppers on SPS (sodium polyanethol sulfonate) tubes have a paler yellow color, sometimes causing confusion; these are known as "yellow tops", not "gold". Trademarked versions of the SST include Covidien "Corvac" tubes.
Features
The tubes have micronized silica particles which help clot the blood before centrifugation, and a gel at the bottom which separates whole blood cells from serum.{{Cite web |title=Greiner Bio-One VACUETTE Z Serum Sep Clot Activator Tubes - Non-ridged (pull cap) | work = Blood, Hematology and Coagulation Testing Products, Blood Specimen Collection |url=https://www.fishersci.com/shop/products/serum-tubes-clot-activator-gel-separator/22040536 |access-date=2022-12-16 | publisher = Thermo Fisher Scientific Inc. |language=en}} Silica nanoparticles induce coagulation through contact activation of coagulation factor XII (Hageman factor).{{cite journal | vauthors = Ilinskaya AN, Dobrovolskaia MA | title = Nanoparticles and the blood coagulation system. Part II: safety concerns | journal = Nanomedicine | volume = 8 | issue = 6 | pages = 969–981 | date = June 2013 | pmid = 23730696 | pmc = 3939602 | doi = 10.2217/nnm.13.49 }} The silica particles are desiccants, which adsorb and hold water vapor.{{cite web | vauthors = Vogelbaun L | date = 14 March 2014 | work = BrainStuff - HowStuffWorks | publisher = YouTube |title=How Does Silica Gel Work? |url=https://www.youtube.com/watch?v=2OsLyBXH3rA |language=en |access-date=2022-12-16}} This is used in the tubes so the blood adheres to the surface of the tiny silica particles and begins to clot. After the blood sample is centrifuged, the clear serum should be removed for testing.{{cite web|url=http://www.ces.purdue.edu/extmedia/AS/AS-557-W.pdf | vauthors = Mitchell B, Neary M, Kelly G |title=Blood sampling in sheep |archive-url=https://web.archive.org/web/20070203031547/http://www.ces.purdue.edu/extmedia/AS/AS-557-W.pdf |archive-date=2007-02-03 |publisher=Purdue University Cooperative Extension Service |date=2003}}{{cite journal | vauthors = Thavasu PW, Longhurst S, Joel SP, Slevin ML, Balkwill FR | title = Measuring cytokine levels in blood. Importance of anticoagulants, processing, and storage conditions | journal = Journal of Immunological Methods | volume = 153 | issue = 1–2 | pages = 115–124 | date = August 1992 | pmid = 1381403 | doi = 10.1016/0022-1759(92)90313-i }}
Use
These tubes should be used with care when measuring drug or hormone levels because the drug or hormone may diffuse from the serum into the gel, causing a reduction in measured level.
The gel in SST II tubes (which appears slightly less opaque) is supposed {{Weasel inline|date=October 2018}} to have less effect on drug levels in serum. {{Citation needed|reason= Who says this? here|date=October 2018}}
Blood samples should be allowed time to form a clot at room temperature for 30–60 min.{{cite journal | vauthors = Tuck MK, Chan DW, Chia D, Godwin AK, Grizzle WE, Krueger KE, Rom W, Sanda M, Sorbara L, Stass S, Wang W, Brenner DE | title = Standard operating procedures for serum and plasma collection: early detection research network consensus statement standard operating procedure integration working group | journal = Journal of Proteome Research | volume = 8 | issue = 1 | pages = 113–117 | date = January 2009 | pmid = 19072545 | pmc = 2655764 | doi = 10.1021/pr800545q }}
CDC recommends a range of time to allow clot formation that was reasonably consistent, from a minimum of 30 min to 60 min maximum.{{cite web | title = Collecting, Preparing, and Shipping Serum Specimens to CDC for Serology Testing | publisher = U.S. Centers for Disease Control and Prevention | url = https://www.cdc.gov/anthrax/pdf/serology-collection-shipping-final-jul2016-508.pdf }}