University of Tübingen: New rapid test developed for the detection of corona antibodies

An international research team from the Universities of Paraná (Brazil) and Tübingen has developed a rapid test that can reliably detect antibodies against the Covid-19 pathogen SARS-Cov2 in the blood within minutes. As the researchers reported in the journal ACS Sensors, the new method can be carried out without expensive instruments due to a simple measuring principle and is therefore also suitable for mobile test stations or for laboratories in economically less developed regions. The new diagnostic method is also significantly faster than the so-called ELISA method, which has been the gold standard in laboratory diagnosis of antibodies for decades.

“Only a small amount of sample is required for the test: just one drop is enough, which contains two microliters of serum,” said the first author of the study, Professor Luciano F. Huergo from the University of Paraná: “It is also possible to use whole blood, This means that the normally necessary separation of the soluble blood components can be omitted for the diagnosis. ”This enables the test to be used at care and test stations on site. “A fully equipped laboratory and the use of special devices are not absolutely necessary for the implementation”. In addition, the total reaction time is 15 times shorter than that of the classic ELISA test, as Huergo explains: “This means that hundreds of samples can be tested in a few hours. “

The new test procedure is based on magnetic nanoparticles coated with viral antigens. To perform the test, blood serum or blood is applied to the test surface. After about two minutes, the nanoparticles are washed and treated with a developer reagent. If the blood sample shows antibodies against the coronavirus, the color changes. While the result of the traditional ELISA test is available after about three hours, the new method requires only twelve minutes according to the results of the study.

Can be used on acutely ill and convalescent patients
Antibodies against the coronavirus SARS-CoV-2 generally develop eleven to 16 days after the onset of symptoms. However, some patients produce detectable levels of antibodies as early as two to four days after the first symptoms of the disease. Immunological tests can therefore be used as additional tools to identify patients in the acute phase of Covid-19 disease or patients who were tested as false negative in the PCR test.

“Our test performed better than the ELISA method, especially for samples with low antibody titers,” said Professor Karl Forchhammer from the Interfaculty Institute for Microbiology and Infection Medicine at the University of Tübingen. “The method worked with a sensitivity of 87 percent and a specificity of 99 percent of the Covid-19 samples tested.” Positive and negative results could be detected with the naked eye. By using additional instruments, such as a microplate reader, the precision of the test can be further increased. “Another advantage over the ELISA method is that the color result of our new method is directly proportional to the antibody concentration,” said Huergo.

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