Types of Vacuumized Tubes for Blood Tests
| Color of Stopper | Substance in Tube | Action of Substance | Tests Used/Not Used for |
|---|---|---|---|
Red, pink | None | None | Used for tests in which serum is required (e.g., many chemistry and serology tests); serum is plasma that has been withdrawn from the body and in which the fibrinogen has been used during normal coagulation of the sample Not used for test requiring whole, uncoagulated blood |
| Lavender, purple | Ethylenediaminetetra-acetic acid (EDTA) | Blocks coagulation by binding calcium Causes minimal distortion of the size and shape of blood cells Prevents platelet aggregation | Used mainly for hematology tests |
| Light blue | Sodium citrate | Blocks coagulation by binding calcium May result in dilution of the specimen due to volume needed to anticoagulate the sample | Most frequently used in coagulation studies Not used for cell counts or chemistry studies |
| Green (navy blue, tan) | Sodium heparin | Prevents coagulation by blocking the action of thrombin Does not alter blood cell size May cause a bluish background when blood smears are stained | Used for red blood cell osmotic fragility studies May also be used for selected chemistry and toxicology studies Not used for coagulation studies |
| Gray | Sodium fluoride and potassium oxalate | Blocks coagulation by binding calcium Blocks action of enzymes in red blood cells, which break down glucose and alcohol May also inactivate cardiac and liver enzymes | Used primarily for blood glucose and alcohol testing Not used for blood glucose tests if the laboratory uses an enzyme testing procedure for determining blood glucose levels Not used for studies of cardiac and liver enzymes |
| Black | Sodium oxalate | Blocks coagulation by binding calcium May distort blood cells May result in dilution of the specimen due to the volume needed to anticoagulate the sample | Used for coagulation studies Not used for blood smears, cell counts, or chemistry tests |
| Yellow | Sodium polyanethol sulfonate (SPS) | Blocks coagulation Inactivates white blood cells and antibiotics | Used primarily for blood cultures (blood sample must be added to blood culture bottle containing additional SPS withing 1 hour of obtaining sample) |