by Shahbaz Ahmed
Vacuum fills the evacuated collection tubes with a predetermined volume of blood. Availability of different sizes of tubes makes them easy to use for pediatric and small volume collections. The tubes can have different additives or coatings so the mixing of blood from one tube to another should not be done. When blood is collected, it mixes with the different additives present in the tubes Color coding of the plastic caps specifies the additives contained in that test tube.
The additives may include anticoagulants (EDTA, sodium citrate, and heparin) or a gel with intermediate density between blood cells and serum. Some tubes contain substances that preserve certain chemicals or substances within the blood, such as glucose. When the serum separator tube is centrifuged, the blood cells sink to the bottom of the tube, are covered by a layer of the gel, and the serum is left on top. The gel enables the tube to be tipped upside-down and transported without the blood cells remixing with the serum. When a tube that does not contain gel or a clotting agent is centrifuged, the clear liquid is plasma, which contains platelets.
Manufacturers standardize the colors for additives in collection tubes for Phlebotomy. Gold or ‘Tiger’ Red/Black top: Used in chemistry, immunology and serology determinations. Contain clot activator and gel for serum separation, and no other additives. Orange or Grey/Yellow ‘Tiger’ Top: Used for STAT serum testing. Contain Thrombin, which is a rapid clot activator.
Green: have Sodium Heparin or Lithium Heparin which inactivates thrombin and thromboplastin, used for plasma determinations. For lithium level, sodium heparin is used. Use sodium or lithium heparin for ammonia level. Light Green or Green/Gray ‘Tiger’: contain anticoagulant lithium heparin, Plasma Separating Tube (PST), used in blood chemistry. Plasma is separated at the bottom of the tube with PST gel.
Purple or lavender: Purple tubes are used when whole blood is required for complete blood counts (CBC) and blood smears or blood typing, and screening in blood banking procedures. Tubes contain EDTA (the potassium salt of EDTA) which is a strong anticoagulant. To prevent clotting and platelet clumping full draw and mixing 8 times is required. Grey: Specifically used for blood glucose determination, requires full draw. Sodium fluoride and Potassium oxalate are present in the tubes. Glycolytic enzymes in the blood are inhibited by Fluoride so glucose is not used up during storage. Anticoagulant used is Oxalate.
Light blue: A reversible anticoagulant Sodium citrate in measured amount is present. Used for coagulation assays (Prothrombin time, Partial Thromboplastin Time). Full draw is essential since dilution factor with liquid citrate should be maintained. Dark Blue: anticoagulant sodium heparin is added, sometimes contain EDTA as an additive or contain no additive. These tubes are used for trace metal analysis and toxicology tests. Pink: contain Potassium EDTA similar to purple tubes, pink tubes are used for blood banking and Molecular/viral load testing .
Red tubes (glass): Tests for antibodies, chemistries, and drugs used these tubes as they contain no additives. Blood cells and serum is separated by centrifugation. Light yellow: Blood culture specimens use tubes which contain sodium polyanethol sulfonate (SPS). Acid-Citrate-Dextrose (ACD) as an additive is used for blood bank studies, HLA phenotyping, and parental testing. Tan: These tubes are certified not to contain lead, hence used for lead determinations. Tubes contain sodium heparin or potassium EDTA.
In addition to teaching collection techniques, correct procedures and order of draw as specified by NCCLS, accredited phlebotomy training courses, also prepare the phlebotomist for understanding proper laboratory procedures in order to avoid contamination or infection control requirements and prepare the phlebotomist to handle emergency situations.
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Tube tops are color coded to indicate the additive present.
Vacuum fills the evacuated collection tubes with a predetermined volume of blood. Availability of different sizes of tubes makes them easy to use for pediatric and small volume collections. The tubes can have different additives or coatings so the mixing of blood from one tube to another should not be done. When blood is collected, it mixes with the different additives present in the tubes Color coding of the plastic caps specifies the additives contained in that test tube.
The additives may include anticoagulants (EDTA, sodium citrate, and heparin) or a gel with intermediate density between blood cells and serum. Some tubes contain substances that preserve certain chemicals or substances within the blood, such as glucose. When the serum separator tube is centrifuged, the blood cells sink to the bottom of the tube, are covered by a layer of the gel, and the serum is left on top. The gel enables the tube to be tipped upside-down and transported without the blood cells remixing with the serum. When a tube that does not contain gel or a clotting agent is centrifuged, the clear liquid is plasma, which contains platelets.
Manufacturers standardize the colors for additives in collection tubes for Phlebotomy. Gold or ‘Tiger’ Red/Black top: Used in chemistry, immunology and serology determinations. Contain clot activator and gel for serum separation, and no other additives. Orange or Grey/Yellow ‘Tiger’ Top: Used for STAT serum testing. Contain Thrombin, which is a rapid clot activator.
Green: have Sodium Heparin or Lithium Heparin which inactivates thrombin and thromboplastin, used for plasma determinations. For lithium level, sodium heparin is used. Use sodium or lithium heparin for ammonia level. Light Green or Green/Gray ‘Tiger’: contain anticoagulant lithium heparin, Plasma Separating Tube (PST), used in blood chemistry. Plasma is separated at the bottom of the tube with PST gel.
Purple or lavender: Purple tubes are used when whole blood is required for complete blood counts (CBC) and blood smears or blood typing, and screening in blood banking procedures. Tubes contain EDTA (the potassium salt of EDTA) which is a strong anticoagulant. To prevent clotting and platelet clumping full draw and mixing 8 times is required. Grey: Specifically used for blood glucose determination, requires full draw. Sodium fluoride and Potassium oxalate are present in the tubes. Glycolytic enzymes in the blood are inhibited by Fluoride so glucose is not used up during storage. Anticoagulant used is Oxalate.
Light blue: A reversible anticoagulant Sodium citrate in measured amount is present. Used for coagulation assays (Prothrombin time, Partial Thromboplastin Time). Full draw is essential since dilution factor with liquid citrate should be maintained. Dark Blue: anticoagulant sodium heparin is added, sometimes contain EDTA as an additive or contain no additive. These tubes are used for trace metal analysis and toxicology tests. Pink: contain Potassium EDTA similar to purple tubes, pink tubes are used for blood banking and Molecular/viral load testing .
Red tubes (glass): Tests for antibodies, chemistries, and drugs used these tubes as they contain no additives. Blood cells and serum is separated by centrifugation. Light yellow: Blood culture specimens use tubes which contain sodium polyanethol sulfonate (SPS). Acid-Citrate-Dextrose (ACD) as an additive is used for blood bank studies, HLA phenotyping, and parental testing. Tan: These tubes are certified not to contain lead, hence used for lead determinations. Tubes contain sodium heparin or potassium EDTA.
In addition to teaching collection techniques, correct procedures and order of draw as specified by NCCLS, accredited phlebotomy training courses, also prepare the phlebotomist for understanding proper laboratory procedures in order to avoid contamination or infection control requirements and prepare the phlebotomist to handle emergency situations.
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