Scientists have developed a quick, sensitive test for antibodies against the novel coronavirus in human blood that could help doctors track a person's exposure to COVID-19, as well as confirm suspected cases that tested negative by other methods.
Because COVID-19 symptoms range from mild to severe, with some people apparently having no symptoms, the number of people who have been infected with the SARS-CoV-2 virus at some point is likely much higher than the number of confirmed cases, the researchers said.
Although more research needs to be done, it is possible that people with antibodies to the virus could be immune to future COVID-19 outbreaks, according to the research published in the journal Analytical Chemistry.
To help identify people with current or past exposure to SARS-CoV-2, the researchers, including those from Southern Medical University in China, wanted to develop a fast, sensitive antibody test.
They based their test on a technique called a lateral flow immunoassay (LFA); a home pregnancy test is an example of this kind of assay.
The team attached a viral coat protein to a specific region on a strip of nitrocellulose, and then added human serum.
The serum flowed from one end of the strip to the other, and any antibodies against the viral protein bound to that region on the strip.
The researchers then 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, they said.
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, they said.
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.
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