Serum is an important sample for clinical biochemical detection. At present, the main way to obtain serum samples is to collect venous blood and centrifuge after blood coagulation. Under normal circumstances, blood samples in vitro need more than 60 minutes to complete coagulation, or even no coagulation, which is difficult to meet the needs of laboratory rapid detection. At this time, blood samples need to be processed to speed up the speed of blood coagulation. The commonly used method to promote blood coagulation is to add some coagulants, such as clay and cephalin, into the collected blood samples. When these coagulants are added into the blood appropriately, they can provide the active surface for coagulation factors to contact with foreign bodies and activate coagulation factors.
Several factors affecting the effect of coagulation promotion are as follows
1. Coagulation rate: blood coagulation mechanism is a process in which a series of coagulation factors are activated successively and finally form fibrin clots. Sometimes, there are filaments and lumps of fibrin in the vacuum blood collection vessel containing coagulant, which is caused by the lack of standardized use of coagulant promoting blood collection vessel.
In the preparation of vacuum blood collection vessel, the selection of coagulant with too fast coagulation speed will lead to the rapid contraction of fibrin, and the fragility of red blood cells will be broken, resulting in mild hemolysis. The proportion of blood clot is greater than that of serum, so the serum is under the upper blood clot, and the lower end of serum is still in contact with the upper end of blood cell. The cells can still use the nutrients in the serum to reduce the blood glucose measurement value, lactate dehydrogenase and serum potassium determination When using the gel accelerating tube, the specific gravity of the gel is higher than that of the blood clot. Therefore, the upper layer is the serum, the middle layer is the separation gel, and the lower layer is the blood clot. Therefore, the various components in the serum maintain physiological levels.
2. Coagulation temperature: the natural coagulation of blood is related to temperature. Blood can coagulate in a glass tube in a 37 ° water bath for 30 minutes. However, it should be pointed out that if the blood and coagulant are not fully mixed or the blood is not completely coagulated, it is easy to form fibrin gel like coagulation or fibrin filaments, whose specific gravity is smaller than the blood clot, so it remains in the serum layer and partially adheres to the separation gel. If the blood is directly used at this time, the blockage of the automatic analysis blood sampling needle can be caused.
3. Dosage of coagulant: the relative amount of coagulant needed to make blood reach the best coagulation effect. When the coagulant was used up on the next day, the coagulant was not prepared well on the next day. Fibrinogen in the blood gradually changes into insoluble fibrin under the action of coagulant. If the coagulation time is prolonged due to insufficient or ineffective coagulant dosage, centrifugation can lead to the precipitation of fibrin.
4. Whether the operation is standard or not: there are the following reasons for the precipitation of fibrin: the coagulant should be slightly reversed and mixed 4-5 times in order to make the coagulant evenly distributed in the blood, so that the center of the blood collection vessel and the surrounding blood coagulate at the same time. If the blood is not completely coagulated, that is, centrifugation can cause the precipitation of fibrin. Gel like and fragment like appeared in the upper part of serum and mixed with blood. Fibrin filaments are caused by the incomplete contraction of fibrin.
The coagulant should be sprayed quantitatively and dried under the condition of less than 45 ° C; if it is higher than 50 ℃, the coagulant effect may decrease. The coagulant prepared with distilled water or anhydrous ethanol should have standard quality management and be sprayed quantitatively. Only by using the coagulant tube containing neutralizing heparin to separate serum can high quality serum samples be separated correctly.
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