Novel antibody test detects Covid without blood sample

Researchers in Japan have developed a new antibody-based method for the rapid and reliable detection of SARS-CoV-2 that does not require a blood sample. The ineffective identification of SARS-CoV-2-infected individuals has severely limited the global response to the COVID-19 pandemic, and the high rate of asymptomatic infections (16-38 per cent) has exacerbated this situation, the researchers said, according to a report in PTI.

One of the methods for the confirmation of COVID-19 infection involves the detection of SARS-CoV-2-specific antibodies. Testing strips based on gold nanoparticles are currently in widespread use for point-of-care testing in many countries.

These tests produce sensitive and reliable results within 10-20 minutes, but they require blood samples collected via a finger prick using a lancing device. This is painful and increases the risk of infection or cross-contamination, and the used kit components present a potential biohazard risk, the researchers said, the PTI report added.

"To develop a minimally invasive detection assay that would avoid these drawbacks, we explored the idea of sampling and testing the interstitial fluid (ISF), which is located in the epidermis and dermis layers of human skin," said Leilei Bao from the University of Tokyo.

"Although the antibody levels in the ISF are approximately 15-25 per cent of those in blood, it was still feasible that anti-SARS-CoV-2 IgM/IgG antibodies could be detected and that ISF could act as a direct substitute for blood sampling," said Bao, lead author of the study published in the journal Scientific Reports.

After demonstrating that ISF could be suitable for antibody detection, the researchers developed an innovative approach to both sample and test the ISF.

"First, we developed biodegradable porous microneedles made of polylactic acid that draws up the ISF from human skin," said Beomjoon Kim, senior author of the study.
"Then, we constructed a paper-based immunoassay biosensor for the detection of SARS-CoV-2-specific antibodies," Kim said.

By integrating these two elements, the researchers created a compact patch capable of on-site detection of the antibodies within three minutes, said the PTI report.
This novel detection device has great potential for the rapid screening of COVID-19 and many other infectious diseases, and is safe and acceptable to patients, the researchers said.

It holds promise for use in many countries regardless of their wealth, which is a key aim for the global management of infectious disease, they added.