Researchers develop a fast, sensitive antibody blood test for COVID-19

A team of researchers here has developed a quick, sensitive test of antibodies against Coronavirus in human blood, which could help doctors track a person's exposure to the disease, as well as confirm suspected Covid-19 cases which have been tested negative by other methods.

Published in the journal Analytical Chemistry, the study revealed that researchers from China wanted to develop a fast, sensitive antibody test to help identify people with current or past exposure to novel Coronavirus.

The researchers based their test on a technique called lateral flow immunoassay (LFA); a home pregnancy test is an example of this kind of assay. They attached a viral coat protein to a specific region on a strip of nitrocellulose -- a highly flammable compound formed by nitrating cellulose through exposure to nitric acid -- and then added human serum. The serum flowed from one end of the strip to the other, and an antibody against the viral protein bound to that region on the strip. Then, the team detected the anti-SARS-CoV-2 antibodies with a fluorescently labelled antibody.

This fluorescence-based detection is much more sensitive than some other LFAs, such as pregnancy tests, that can be read by the naked eye. According to the study, the researchers tested the new assay on seven serum samples from Covid-19 patients and 12 samples from people who had tested negative for the disease by reverse transcriptase-polymerase chain reaction (RT-PCR), a common diagnostic test that occasionally fails to detect positive cases.

The new assay correctly diagnosed all seven samples as positive -- as well as an additional 'negative' case that had suspicious clinical symptoms -- in only 10 minutes per sample.

The immunoassay could be helpful in confirming negative diagnoses, monitoring a patient's recovery, studying past exposures, and identifying recovered individuals with high levels of antibodies as potential convalescent plasma donors, the researchers said.