Blood Collection Tubes and Tests

Blood Collection Tubes

    Most blood collection tubes contain an additive that either accelerates clotting of the blood (clot activator) or prevents the blood from clotting (anticoagulant). A tube that contains a clot activator will produce a serum sample when the blood is separated by centrifugation and a tube that contains an anticoagulant will produce a plasma sample after centrifugation. Some tests require the use of serum, some require plasma, and other tests require anticoagulated whole blood.

Why are blood collection tubes color coded?

    The reason why tubes are color-coded is for practical and easy identification. These colors indicate the color of the culture bottles necessary for blood culture. These tubes (bottles) contain sodium polyanethole sulfonate (SPS), which serves as an anticoagulant.

Order of Blood Draw Tubes and Additives

     Blood samples must be drawn by phlebotomists in a specific order to avoid cross-contamination of the sample by additives found in different collection tubes. Phlebotomy order of draw is the same for specimens collected by syringe, tube holder, or into tubes preevacuated at the time of collection. The correct order of draw follows:

Blood culture tube or bottle

1.Sodium citrate tube (eg, blue closure)
2.Serum tubes, including those with clot activator and gels (eg, red, red-speckled, gold closures)
3.Heparin tube with or without gel (eg, dark green, light green, speckled green closures)
4.EDTA tube with or without gel separator (eg, lavender, pearl, pink closures)
5.Sodium fluoride/potassium oxalate glycolytic inhibitor (eg, gray closure)

    The placement of tubes not listed here should take into consideration the potential for their additive to alter results obtained from the next tube if carryover were to occur. Plastic serum tubes containing a clot activator may cause interference in coagulation testing. Only blood culture tubes, glass nonadditive serum tubes, or plastic serum tubes without a clot activator may be collected before the coagulation tube.

  The most commonly used blood collection tubes.

Tube cap color	Additive	Function of Additive	Common laboratory tests
Light-blue	3.2% Sodium citrate	Prevents blood from clotting by binding calcium	Coagulation
Red or gold (mottled or "tiger" top used with some tubes)	Serum tube with or without clot activator or gel	Clot activator promotes blood clotting with glass or silica particles. Gel separates serum from cells.	Chemistry, serology, immunology
Green	Sodium or lithium heparin with or without gel	Prevents clotting by inhibiting thrombin and thromboplastin	Stat and routine chemistry
Lavender or pink	Potassium EDTA	Prevents clotting by binding calcium	Hematology and blood bank
Gray	Sodium fluoride, and sodium or potassium oxalate	Fluoride inhibits glycolysis, and oxalate prevents clotting by precipitating calcium.	Glucose (especially when testing will be delayed), blood alcohol, lactic acid