Training In Phlebotomy: Color Codes For Function
Those brightly colored rubber caps you see on blood collection tubes aren’t a fashion statement — they’re a form and function statement. That’s why anyone training in phlebotomy will be expected to identify what those color-coded stopper tops mean.
In fact, that color-coded system recommended by the Clinical and Laboratory Standards Institute (CLSI) is so important to the patient’s health that it is imperative those training in phlebotomy thoroughly memorize the meaning of each color.
In most cases, the tube’s stopper color is used to identify a particular type of additive that has been placed in the tube — either liquid, spray dried or powdered — by its manufacturer for a specific purpose. Almost all tubes in the evacuated tube system today contain some additive, and occasionally, there may be more than one stopper color for the same additive.
The most common additives are categorized by function; some may or may not cause the blood to clot. If it’s intent is to prevent clotting (such as the anti-coagulants EDTA), citrates, heparin and oxalates), then the ordering physician is asking for a whole blood specimen which may be used directly for testing or may need to be centrifuged to separate the cells from plasma. If the additive is there to activate clotting, the blood sample will be centrifuged to obtain a fluid portion referred to as serum.
Sometimes, however, the stopper color indicates a special property of the tube. A royal blue stopper, for instance, indicates that the tube contains no trace elements.
Some of the more common tube stopper colors and their function are:
— A light blue stopper indicates a tube that contains a sodium citrate additive to prevent clotting, and will be used for a variety of routine coagulation tests.
— A gold or ‘tiger’ or red/black stopper indicates an additive that causes clotting, and is for specimens used in chemistry, immunology and serology.
— Green-stoppered tubes contain sodium heparin or lithium heparin and are used for plasma determinations
— Light green or green/gray ‘tiger’ stoppers are for plasma separating tubes with lithium heparin, and is used in blood chemistry.
— Purple or lavender stoppers are used when whole blood is required for complete blood counts (CBC) and blood smears or blood typing, and screening in blood banking procedures. These tubes contain the anticoagulant.
— Grey stoppers are used on tubes containing glycolytic enzyme inhibitors and used for blood glucose determination.
The color codes are a vital part of the phlebotomists’ order of draw, helping to ensure accurate test results and minimizing the chance of contamination. The order of draw, as recommended by both the CLSI and National Healthcareer Association, is as follows:
- Sterile blood culture tubes or vials
- Blue-top (sodium citrate) coagulation tube
- Red-topped serum tube with or without clot activator, with or without gel
- Green-stoppered (heparin) tube, with or without gel plasma separator
- Lavender stopper tubes containing EDTA
- Gray stopper (glycolytic inhibitor) tubes
- Sterile tube (blood culture)
- Blue-top coagulation tube
- Serum tube with or without clot activator, with or without gel
- Heparin tube with or without gel plasma separator
- EDTA tube
Phlebotomists should ensure that this order of draw be followed for every draw. A sterile tube drawn after another tube is no longer sterile and contaminates the specimen. Similarly, trace amounts of EDTA on a needle can negatively affect the clotting results in the next draw.
For students training in phlebotomy, the color of the tube’s stopper says plenty — the wise phlebotomist listens.