Understanding the "Colorful" Plain Tube for Blood Collection, No Panic When Drawing Blood!

Plain Tube for Blood Collection of Different Colors Meet Different Needs

When undergoing a medical check-up or visiting a doctor in a hospital, you will often see this scene: a nurse takes out a variety of plain tubes for blood collection of different colors to draw blood from a patient. Some may wonder: why can't just one tube of blood be drawn to lessen the pain?

In fact, drawing more than one tube of blood and using different colored tubes is not for aesthetics, but necessary for testing. These colorful plain tubes for blood collection represent different purposes; each color-coded plain tube for blood collection contains specific additives, which serve different testing needs.

Uses of Different Colored Plain Tube for Blood Collection

Actually, using different colored plain tube for blood collection is not for aesthetics, but necessary for testing. These colorful plain tubes for blood collection represent different purposes; each plain tube for blood collection contains specific additives, which serve different testing needs.

Red Cap Tube

The inner wall of the tube is evenly coated with an agent (silicone oil) to prevent blood from sticking. It uses the natural coagulation process of blood to allow it to clot and is then centrifuged after the serum naturally separates.

Green Cap Tube

This tube contains sodium heparin or lithium heparin. Heparin is a polysaccharide containing sulfated groups with a strong negative charge. It enhances the inactivation of serine proteases by antithrombin III, thereby preventing thrombin formation and also inhibiting platelet aggregation, among other anticoagulant actions. Heparin tubes are typically used for emergency biochemistry, TORCH, and blood rheology testing. When testing sodium ions in blood samples, sodium heparin tubes should not be used as they can affect results. They also should not be used for white blood cell counts and classifications as heparin can cause white blood cell aggregation.

Purple Cap Tube

Ethylenediaminetetraacetic acid (EDTA) is an aminopolycarboxylic acid that effectively chelates calcium ions in the blood. Chelating calcium removes calcium from reaction points, thus preventing and terminating the coagulation process, both intrinsic and extrinsic, thereby preventing blood from clotting. Compared to other anticoagulants, EDTA salts (2K, 3K, 2Na) have a lesser effect on blood cell aggregation and morphology, and are thus commonly used as anticoagulants. They are used for general hematology (complete blood count) tests and ammonia testing. They cannot be used for coagulation and trace element tests.

Blue Cap Tube

Sodium citrate chelates calcium ions in blood samples to provide anticoagulation. The ratio of anticoagulant to blood is 1:9, primarily used for testing the fibrinolytic system (prothrombin time, thrombin time, activated partial thromboplastin time, fibrinogen).

Black Cap Tube

The ratio of anticoagulant to blood volume is 1:4, generally used for erythrocyte sedimentation rate (ESR) testing. When the anticoagulant ratio is too high, the blood is diluted, which can accelerate the sedimentation rate. Care should be taken to collect sufficient blood (2ml) to ensure accurate test results, and the sample should be inverted and mixed 8-10 times immediately after collection.

Each color-coded blood collection tube has its specific use, aimed at ensuring the accuracy of laboratory testing. Medical testing is very stringent, and even a minor deviation can affect a doctor's judgment of the condition. Therefore, using different colored plain tube for blood collection is actually designed to more accurately reflect our health status.