When having blood drawn for laboratory tests, seeing all the different tubes can be a bit overwhelming. The health care professional that is performing the venipuncture is trained to differentiate the different blood tests and tube colors required to collect the specimen.
Coagulant Blood Tests
Coagulant blood tests are performed to test an individual’s ability to clot properly. The test is generally ordered prior to a surgical procedure, when a patient is diagnosed with a bleeding disorder, or if a patient is being treated with blood thinner medications.
Gold or red/gray rubber top tube known as a tiger tube contains a clot activator and gel and is used for serum separation.
Red top tube also has a clot activator and is used to collect serum to test for infectious diseases, or routine blood donor screening.
Orange or grey/yellow rubber top contains thrombin, which is used as a rapid clot activator, used for serum testing required right away.
Anticoagulant Blood Tests
An anticoagulant is added to various different types of tubes to prevent coagulation, or blood clotting from occurring. This additive binds to calcium ions, which inhibits the proteins responsible for coagulation from acting and causing the blood to clot.
Lavender or Pink rubber top tube contains an additive called ethylenediaminetetraacetic acid (EDTA), or potassium salt. This tube is used for full blood counts (CBC) required for blood banks, blood type screening, or blood cross-match.
Light blue top tube contains citrate as an additive, which is a reversible anticoagulant. This additive will dilute the blood and is used for platelet function and coagulation assays.
Green top tubes contain sodium or lithium heparin and used in chemistry for plasma determination.
Light Green or Green/Gray top tubes are similar to the green tube in plasma determination. The difference is this tube contains lithium heparin and a gel for plasma separation.
Grey top tube contains potassium oxalate and sodium fluoride and used for glucose determinations.
Dark blue top tube contains sodium heparin and can also contain EDTA. It is used to analyze if there is trace metal in the blood supply.
Other Types of Tests and Tubes
There are other types of tubes used for various tests that are ordered by a healthcare professional, but are not classified as a coagulant or anticoagulant.
Red top tube, which contains no additives, is used to test for antibodies, or for drug testing.
Light yellow top tube contains the additive sodium polyanethol sulfonate (SPS) or acid citrate dextrose additives. This tube is used for blood bank studies, human leukocyte antigen (HLA) phenotyping, DNA, and paternity testing.
Tan top tube is used specifically to test for lead and is certified to have less than .01 micrograms per milliliter of lead. The tube contains EDTA as an additive.
White top tube contains EDTA with gel as an additive and is used in molecular diagnostic testing to include polymerase chain reaction (PCR) or branched DNA amplification.
Standard Order of Blood Draw
The order of tubes used in a blood draw is important when collecting a blood sample to prevent cross contamination in the various tubes used. The first draw is the blood culture, then the coagulation tube, non-additive tube, followed by additive tubes. There are variances in the order of tubes used in the collection and the healthcare professional is trained in the appropriate methods.