Problems to be noticed in clinical application of separation gel blood collection tube

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Separation gel blood collection tubes have been widely used in clinical laboratories. Separation gel can form an isolation layer between cell components and serum (plasma), effectively prevent the exchange of substances between blood cells and serum (plasma), and ensure serum (plasma) within a certain period of time. ) Stability of ingredients. There are generally two types of separation gel blood collection tubes commonly used in laboratories: serum separation gel coagulation tube and plasma separation gel anticoagulation tube.

The serum separating gel coagulation tube is to add a coagulant to the blood collection tube to shorten the blood coagulation time, get the serum quickly, and report the result in the shortest time. The glass blood collection tube does not need to add a coagulant, and blood contact with the glass tube wall will trigger blood coagulation. When the coagulation factors Ⅺ and Ⅻ come into contact with plastic blood collection tubes, their ability to be activated is very weak, and coagulants need to be added to shorten the clotting time. The plasma separator gel anticoagulant tube is sprayed with anticoagulant such as lithium heparin on the inner wall of the separator gel blood collection tube to meet the needs of rapid plasma biochemical emergency testing.

In practical applications, it is often encountered that the separation effect of the separation gel blood collection tube is not good, for example: in some separation tubes, there are separation gel fragments or oil droplets floating on the surface of the serum or suspended in the serum; the separation gel layer floats on the serum layer Wait up. The separation gel will also interfere with certain test results. In the following, Desheng mainly analyzes from two aspects, namely, the reason for the poor separation effect of the separation gel and the influence of the introduction of the separation gel on the measurement.

1. Reasons for the different specific gravity of separation rubber:

The mechanism of separation gel to separate serum and plasma. The separation gel is a thixotropic mucus colloid composed of hydrophobic organic compounds and silica powder. The structure contains a large number of hydrogen bonds. The existence of hydrogen bonds constitutes the chemical basis of the thixotropy of the separation gel. The specific gravity of the separation rubber is maintained at 1. 05. The proportion of blood liquid components is about 1. 02. The proportion of blood formed components is about 1. 08. When the separation gel and coagulated blood (or anticoagulated whole blood) are centrifuged in the same test tube, the hydrogen bond network structure is destroyed due to the centrifugal force applied to the separation gel and becomes a chain structure, and the separation gel becomes viscosity Low fluid. Due to the difference in specific gravity, the separation gel has reversed phenomenon and stratified into three layers of blood clot (anticoagulated whole blood)/separation gel/serum (plasma). When the centrifuge stops rotating and loses the centrifugal force, the chain-like particles in the separation gel are again formed by hydrogen bonds to form a network structure, which restores the initial high-viscosity gel state, forming an isolation layer between the serum (plasma) and blood clot (anticoagulated whole blood) .

2. Reasons for the poor separation effect of the separation gel

(1) Quality of separation gel

The specific gravity of the separation gel is between serum (plasma) and blood cells, which is the physical basis for the reversibility of the separation gel and the separation of serum (plasma). If the quality of the separation gel for blood collection tubes is poor and the specific gravity cannot meet the requirements, it will inevitably affect the separation of serum (plasma), and the separation gel and serum (plasma) are likely to be intertwined.

(2) Incomplete blood clotting

After centrifugation, sometimes the separation of the separation gel compartment and serum, blood clots is not complete, and fibrin filaments appear in the serum. The reason is often that the blood did not completely coagulate before centrifugation. Insufficient blood coagulation can mix fibrin in the barrier layer. The serum separation hose must be used correctly according to the instructions, and after the blood is completely coagulated (generally plastic tubes containing coagulant should be placed upright for about 30 minutes, blood collection tubes without coagulant should be placed upright for 60 to 90 minutes) and centrifuge to separate the serum. In order to prepare high-quality serum samples.

(3) Centrifugal temperature

The centrifugation temperature has a significant effect on the separation of serum by the gel coagulation tube. In the inert separation gel accelerator tube separated by ordinary centrifuge at room temperature, the serum is clear, but oily beads of different sizes appear in 15% to 20% of the samples. No oily beads were found in the serum separated from the test tube centrifuged in a low-temperature centrifuge. When the temperature exceeds the storage temperature required by the separation hose, the inert separation gel will dissolve in the serum. It will not only block and contaminate the sample needle and reaction cup of the biochemical analyzer, but also have a relatively large impact on the results of some biochemical assays.

(4) Centrifugal operation

Centrifugation is an important part of the preparation of high-quality serum samples with the separation gel coagulation tube. The separation gel of BD Company requires that immediately after blood collection, it is required to gently invert and mix at 180° for 8 to 10 times, and place it upright for 30 minutes. After the sample is fully coagulated, use the horizontal type. Centrifuge for 10 minutes in a centrifuge, and maintain the centrifugal force at 1 300 2 000 × g, so that the serum (plasma) and the blood clot are completely separated by the separating gel. If the centrifugal force is too low, the force acting on the separation gel will be weak, making the separation gel poorly reversible. Fibrin condensate may stay in the serum or colloid layer, which can easily block the sample needle of the automatic analyzer. On the contrary, if the centrifugation time is too long, it is difficult to form a network structure after the hydrogen bond is cut in the separation colloidal aggregate, and the thixotropy is lost.

(5) Serum/plasma density

Fatás et al. discovered the abnormal phenomenon that the separation gel layer is located above the plasma layer, and used physiological saline solutions of dextran with different density and viscosity to simulate blood in different states to study the reason why the separation gel cannot separate serum/plasma normally. It is found that the density of serum (plasma) is the main reason that affects the floating of the separating gel, not the viscosity. Any factor that causes the density of serum (plasma) to increase and exceeds the density of the separation gel can cause abnormal reversal of the separation gel. For example: high total protein (TP), high blood sodium, angiography, etc. Such blood samples should be collected using blood collection tubes without additives, and the collection should be performed at an appropriate time.

3. Reasons for the different components of the separating gel

Although the components of the separation gel are inert to the blood, it cannot be guaranteed that it will not affect all manufacturers' detection systems and all items. There are many manufacturers of blood collection tubes, and each company has different components and ratios of the separation gel, and unique materials are mixed to maintain its stability. Therefore, the transparency, color and performance of the separation gel of each company are different. In terms of impact on the test results, some manufacturers' blood collection tubes interfere with certain routine items, such as LI+, TG, homocysteine, etc. The interference of some manufacturers (mainly imported blood collection tubes) on the test is only concentrated in some special items, such as methadone, triiodothyronine, total free fatty acids, etc. The separation gel may also bind to certain hydrophobic drugs, causing its concentration to decrease. Separating gel or oil droplets floating on the surface of the supernatant may interfere with the sample needle and reaction cup of the analytical instrument, and may also cause physical interference to the immunological reaction and affect the accuracy of the test results.

4. Reasons for non-standard operation:

Solution In the clinical application of separation gel blood collection tubes, many irregular operations will affect the separation effect, and some separation gel blood collection tubes will interfere with some testing items. These problems are not easy to be found in daily quality control and routine testing. In order to ensure the authenticity and credibility of the test results, it is very important to do a good job of quality control of blood samples before testing.

Desheng has formed independent intellectual property rights and professional production R&D capabilities in blood collection tube additives. Provide products and raw material solutions for more than 100 domestic and foreign manufacturers. Blood sample anticoagulation products include heparin sodium, heparin lithium, trisodium citrate, EDTA dipotassium, EDTA tripotassium, potassium oxalate, etc.; blood sample procoagulant products include blood coagulation powder, blood coagulant, etc.; blood samples The materials used in the pretreatment include separating gel, siliconizing agent and so on.