A team of researchers at the Southern Medical University, Guangzhou, China, and collaborators report development of a rapid diagnostic assay for detection of SARS-CoV-2 antibodies in human blood. They report accurate detection with patient samples, with only 10 minutes to get a readout per blood sample.
The new method is a lateral flow assay, much like a home pregnancy test. Human serum is obtained from a test patient and added onto one side of the device, where it flows through the paper due to capillary action. The researchers impregnated COVID-19 proteins in a thin line on this paper to bind the antibodies. If the anti-COVID-19 antibodies are present, they will bind along this line, else, there will be no binding activity. To improve resolution, the researchers also use secondary binding of rabbit anti-human IgG antibodies, linked with a fluorescent reporter, allowing for greater accuracy than an unassisted visual readout.
The researchers tested the assay on seven serum samples from known COVID-19 positive patients, and twelve patients indicated as negatives by RT-PCR. The new assay correctly diagnosed all seven samples as positive, and a negative case that had suspicious clinical symptoms was also found to contain COVID-19 human antibodies. The test took only 10 minutes per patient and the researchers say the test could help confirm negative diagnosis, monitor COVID-19 recovery, study past exposure, and identify recovered individuals with high antibody levels as plasma donors.
The publication in journal Analytical Chemistry: Rapid and sensitive detection of anti-SARS-CoV-2 IgG using lanthanide-doped nanoparticles-based lateral flow immunoassay