Tubes and Additives
Blood collection tubes come in many different sizes with different color stoppers that represent the type of additive inside the tube. Most of them are now made of safety-engineered plastic instead of glass, for safety and the lessened chance of one breaking should it be dropped. The tubes are designed with markers that indicate the amount of specimen to be collected into it. Blood collection tubes can come in sterile or non-sterile. Many tubes are designed to perform directly with testing instruments, in that the tube is identified by the barcode on the label and pierced by the machine to extract blood, plasma, or serum for testing. Many labs are moving toward using heparinized whole blood specimens to cut down on processing time, because you eliminate the need to centrifuge the sample.
Additives are used to either keep blood from clotting (anti-coagulants), or aid in quicker clotting. Anticoagulants often contain preservatives that extend the metabolism of red blood cells (RBC’s) after collection, and are usually used when whole blood or plasma is needed for analysis. Here are the anticoagulants used in blood collection:
- EDTA (ethylene diaminetetraacetic acid)
The first 3 prevent coagulation by removing calcium & forming insoluble calcium salts, this means that they must not be used in the testing of calcium assays. Citrates are usually used in coagulation studies. EDTA is usually used for platelet tests and blood smears. Heparin acts as an anticoagulant by inactivating the blood-clotting chemicals thrombin and factor x . It is used in tests such as ammonia and plasma hemoglobin, and is also used for arterial blood gas samples.
Pediatric tubes also have additives, just less, and they use the same color coding system as the full-sized tubes.
Click here to view and/or print a chart that describes the tubes, the correct order in which they are to be drawn, the additives in each tube, and number of times each tube should be inverted for proper mixing of the blood with the additive.
Q: [Centrifuge] - An apparatus that rotates at high speed and by centrifugal force separates substances of different densities, as in the components of blood. [Image]
Q: [Thrombin] - Thrombin is a biochemical substance that naturally functions as a blood clotting factor to convert fibrinogen to fibrin
Q: [Hemoglobin] - The iron-containing pigment of red blood cells; functions primarily in transporting oxygen from the lungs to the body tissues
Q: [Plasma] - The yellow-colored liquid component of blood, in which blood cells are suspended