Is it possible to freeze blood in vacuum test tubes with gel
Why in a test tube gel?
Sashkov VA, biol. Sci., Associate Professor of Moscow State University. VI Lenin
Kovalevskaya SN, assistant of St. Petersburg State Medical University named after ac. IP Pavlova
An indispensable condition that guarantees the receipt ofreliable results of laboratory analyzes, is the preservation of the primary analytical characteristics of samples of venous blood taken for examination. Exclude the influence of preanalytical factors by using standardized methods for taking, transporting and storing samples. One of the modern options for improving the quality of laboratory tests is the use of a closed method of taking venous blood in vacuum tubes with separation gel.
Gel technologies were first used invacuum test tubes Becton Dickinson for taking blood back in 1970 and can significantly reduce the number of errors in the preanalytical stage. In addition, blood samples in such test tubes are easy to transport and store for a long time, which is especially important in the conditions of centralization of laboratory studies.
An important advantage of the gel is the fact thatwhen centrifuged, it forms a stable barrier between the supernatant and the remaining components of the blood (clot, cells). This allows not only to preserve the stability of the analytes in the sample without the need for secondary tubes, but also to significantly increase the shelf life of the samples.
An important aspect when working with gel tubesis the observance of the recommended speed, time and temperature regime (25 ° C) during centrifugation, the use of centrifuges with an unfixed rotor angle, and also no later than 2 hours after taking blood. Compliance with these simple rules will ensure the formation of a qualitative gel barrier between the supernatant and the blood cells. After centrifugation, blood samples in the test tubes with gel can be frozen for subsequent archival storage. For these purposes, the tubes are cooled to + 4 ° C for 2 hours and then frozen at a rate of -0.5 ° C / min to -20 ° C or -70 ° C.
To obtain a high quality serum samplewith the possibility of convenient and safe transportation of the sample, a tube with a coagulation activator and a separation gel was created. Silica (the blood coagulant activator) is applied by spraying on the inner walls of the tube and provides accelerated clot formation in 30 minutes, and also increases the yield of serum, as compared to conventional serum tubes with a red lid. An inert separation gel based on acrylic can be placed at an angle to the bottom of the tube, which significantly improves separation efficiency. The serum obtained in these test tubes has a longer stability of the analytes, a lower probability of formation of a fibrin clot in the serum, and a frequency of hemolysis during transport.
For express-diagnostic laboratories, especiallythe speed of obtaining the result is important. However, when trying to speed up the procedure for handling samples, laboratory technicians may be tempted to neglect the recommended minimum clotting time.
In this case, after centrifugation of the tubeswith not completely clotted blood in the serum can be formed filaments or even clots of fibrin, which can distort the results of analyzes. This leads to the need to re-take blood, and often to expensive repairs of laboratory equipment. To solve these problems, tubes for the accelerated production of serum were developed, in which thrombin is used as an activator of coagulation. The time of blood coagulation in these test tubes is a record 5 minutes, and the serum turns out to be more pure and qualitative.
In addition to rapid diagnostic laboratories, highThe need for the use of tubes with thrombin and gel can be found in patients on anticoagulant therapy. The production of qualitative serum for biochemical analyzes in such patients is not an easy task due to the presence of exogenous anticoagulants in blood and the "gelling" of blood samples. The use of thrombin as an activator of blood coagulation makes it possible to obtain a qualitative blood sample and to avoid repeated blood sampling and associated additional costs for analyzes.
When carrying out biochemical and other types ofAnalyzes in the health facility often also require the need for rapid plasma analysis, with the possible subsequent archival storage of samples. For this purpose, test tubes with lithium heparin and gel were developed. The use of plasma for routine biochemical tests can also reduce the waiting time for clot formation when using serum. An additional advantage of using plasma in front of the serum is its greater yield from the same blood volume and less risk of formation of fibrin filaments in the sample. Plasma can also be the preferred type of sample for biochemical blood tests in patients on anticoagulant therapy.
Treatment of blood samples during analysis forthe viral load often requires obtaining samples of undiluted plasma of high quality, suitable for ultra-sensitive methods of analysis. When carrying out analyzes for HIV, syphilis, hepatitis, when examining the blood of donors in blood banks for infection, not only is the possibility of transportation and short-term storage of plasma after centrifugation, but also its long-term storage in a frozen form. For these purposes, a tube with K2EDTA and a separation gel was developed. The plasma obtained in these tubes is practically free of erythrocytes and granulocytes, the concentration of monocytes and lymphocytes in it is negligible, and the concentration of platelets can be higher than in whole blood. After centrifugation, the erythrocytes and lymphocytes remain under the gel layer, and the plasma with platelets on top of it. When using these tubes, the plasma can be transported directly in the primary tube after centrifugation. It is important to remember that plasma freezing is unacceptable in certain types of analyzes (to determine the viral load in HIV infection due to damage to RNA viruses during the freezing / thawing of the sample).
Thus, it is possible with confidenceto state that gel technologies significantly reduce the time for obtaining high-quality blood samples for various laboratory analyzes, allow to obtain high-quality samples and solve the problem of their transportation and long-term storage of the sample, to shorten TAT, which is especially important in the conditions of centralization of laboratory studies.