Based on the color of the cap, venous blood collection tubes are mainly divided into the following types:
1. Green-capped tubes: Contain lithium heparin. Heparin tubes are generally used for biochemical and hemorheological tests and are the best choice for electrolyte testing. Because heparin can cause white blood cell aggregation, it cannot be used for white blood cell counting and differential diagnosis.
2. Red-capped tubes: The inner wall of the tube is evenly coated with silica to prevent adhesion and contains a coagulant. They are generally used for serum immunological tests such as hepatitis virus, thyroid function, drug testing, HIV testing, and tumor markers.
3. Purple-capped tubes: Contain ethylenediaminetetraacetic acid (EDTA) and its salts, usually using EDTA salts as an anticoagulant. Used for general hematological tests such as blood cell counts and differential diagnosis, but not for coagulation, trace element, or PCR tests.
4. Blue-capped tubes: Contain sodium citrate and are mainly used for the detection of fibrinolytic system parameters (prothrombin time, thrombin time, activated partial thromboplastin time, fibrinogen). When collecting blood, please ensure sufficient blood volume and avoid any gaps in the tube that could affect the accuracy of the test results. After blood collection, immediately invert and mix the tube 5-8 times.
5. Black-headed tube: This tube contains sodium citrate and is generally used for erythrocyte sedimentation rate (ESR) testing. When the anticoagulant ratio is too high, the blood is diluted, which can accelerate the ESR.
