The test strip will determine the blood type
A centrifuge for typing blood was placed in a flash drive
Denis Strigun, Naked Science
Chinese scientists have developed a one-time rapid test on a paper basis, which allows to determine a person's blood type with an accuracy of more than 99.9 percent. The results of the study are published in Science Translational Medicine (Zhang et al., A dye-assisted paper-based point-of-care assay for fast and reliable blood grouping).
The ability to quickly and accurately determine the blood type is important in emergency situations, since a large volume of blood transfusion with incompatibility increases the risk of death of the recipient. According to the indicator of such mortality, the most important are the AB0 and Rh blood typing systems. The criterion of the AB0 system is the presence of agglutinins α and β in plasma and agglutinogens A and B in erythrocytes. Combinations of these proteins correspond to four blood groups: 0, or I (α and β), A, or II (A and β), B, or III (B and α), AB, or IV (A and B). In turn, the Rh system types blood by the presence of specific types of immune antigens on erythrocytes, the most common of which, type D, indicates a "positive" (presence of antigen) or "negative" (absence of antigen) Rh factor. In total, the Rh system takes into account 50 antigens, including types C, c, E and e.
Modern blood typing technologies based on the use of special tablets or workstations require a relatively long time (from 30 minutes) and high qualifications. In particular, to increase the reliability of the results, typing according to the AB0 system is cross-sectional and is carried out by direct and reverse methods. In this case, the samples are pre-centrifuged
they are divided into erythrocytes and plasma. Whereas the existing prototypes of express tests are not designed for direct and reverse analyses for both typing systems and are characterized by low reliability.
In a new article, scientists from the Third Military Medical University presented and tested three variants of an express test for whole blood analysis: typing AB0 by direct method; direct and reverse methods; and parallel typing AB0/Rh. The device is based on the concept of a test on a paper substrate using dye (dye-assisted paper-based assay). The system is a miniature tablet with three or seven wells, a membrane module for sample separation, platforms for plasma and erythrocyte analysis and a plastic case. At the first stage, the sample is placed in the central well, after which it is cleaned with a washing buffer. The membrane separates the sample, and the plasma (thanks to serum albumin) reacts with the bromocresol green indicator, and one of the seven types of antigens (A, B, D, C, C, E, E) on erythrocytes reacts with immunoglobulins M (IgM). Color combinations, clearly distinguishable in the wells, allow you to establish the blood group and Rh factor.
Variants of the test for typing by direct (A) and direct and reverse (B) methods,
multiplex testing (C) for ABO/Rh and for rare blood group systems (D)
(figure from an article in Science Translational Medicine).
According to the authors, 100 microliters of blood is enough for the analysis, which lasts from 30 seconds to two minutes. Comparison with traditional typing technologies also showed that the new test has high accuracy and reliability. Statistically significant error was observed only in the case of extremely rare combinations of antigens. When developing the test, the researchers analyzed 3,550 blood samples typed using a workstation.
In the future, the new technology may also help in the diagnosis of diseases. Previously, scientists created a test that allows detecting the presence of a tumor and, theoretically, its localization by a drop of blood. Another group of specialists showed that this method is also suitable for the diagnosis of multiple sclerosis.
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17.03.2017