Diagnosis in ten minutes
As signs of a smoothing of the COVID-19 incidence curve in the U.S. and other countries have emerged, health officials are trying to figure out how many people have been infected. Since COVID-19 symptoms range from mild to severe, and some have none at all, the number of people infected with the SARS-CoV-2 virus is probably much higher than the number of confirmed cases. As states begin to relax restrictions, large-scale testing of the general population will be important to identify people in the early stages of the disease or people who have no symptoms but who may still infect others. In addition, there is a possibility that people with antibodies to the virus may be immune to future COVID-19 outbreaks. To help identify people with current or past exposure to SARS-CoV-2, a team of researchers has developed a rapid and sensitive antibody test for the virus.
The test is based on lateral flow immunoassay (LFA); a home pregnancy test is an example of this kind of analysis. The researchers placed the viral protein on a strip of nitrocellulose, and then added human blood serum. The serum flowed from one end of the strip to the other, and the antibodies against the viral protein present in it were bound by the viral protein on the strip. The team then detected antibodies against SARS-CoV-2 using fluorescein-labeled antibodies. The fluorescence-based test is much more sensitive than other LFA, such as pregnancy tests, which can be evaluated with the naked eye.
The new test makes it possible to detect antibodies to coronavirus, which manifest as a bright orange line when placed on a fluorescent reader.
The researchers tested the new test on seven serum samples from COVID-19 patients and 12 samples from people who tested negative for the disease using reverse transcription polymerase chain reaction (RT-PCR), a common diagnostic test that sometimes gives false negative results. The new test correctly diagnosed all seven samples as positive, as well as an additional "negative" case that had suspicious clinical symptoms – in just 10 minutes per sample.
According to the researchers, immunoassay can be useful for confirming negative diagnoses, monitoring the patient's recovery, studying past contacts with the virus and identifying recovered people with high levels of antibodies as potential plasma donors.
Article Z.Chen et al. Rapid and Sensitive Detection of anti-SARS-CoV-2 IgG, Using Lanthanide-Doped Nanoparticles-Based Lateral Flow Immunoassay is published in the journal Analytical Chemistry.
Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru based on ACS materials: Sensitive new test detects antibodies against SARS-CoV-2 in only 10 minutes.