May 31, 2020 2:20:46 pm
Scientists at the University of Maryland School of Medicine (UMSOM) have developed an experimental diagnostic test for COVID-19 that can visually detect the presence of SARS-CoV-2 in 10 minutes.
The development comes as the number of cases of the virus continues to rise even as governments of many countries have started loosening restrictions on their residents. With relatively free movement, the chances of the infection spreading are greater and therefore, tests that can deliver results as quickly, like this naked eye test, may be crucial in containing the spread of the disease.
The test uses a highly specific molecule that attaches itself to gold nanoparticles, which is able to detect a specific protein, which is a part of the genetic sequence unique to the virus. The authors have published their findings in the journal ACS Nano.
How does the test work?
Through this “naked eye” test, a nasal swab or a saliva sample is taken from the patient and mixed with a simple laboratory test, which contains a liquid mixed with gold nanoparticles attached to a molecule that binds itself to SARS-CoV-2. If the solution turns to a deep blue colour, it indicates that the virus is present. On the other hand, if the solution does not contain the virus in it, it does not change its colour and retains its purple hue.
In a press release issued by the UMSOM, Dipanjan Pan, PhD, professor of diagnostic radiology and nuclear medicine and pediatrics at UMSOM and the study’s leader was quoted as saying, “Based on our preliminary results, we believe this promising new test may detect RNA material from the virus as early as the first day of infection. Additional studies are needed, however, to confirm whether this is indeed the case”.
How does this method compare with other tests used for coronavirus testing?
This method is faster than other tests such as the conventional RT-PCR test since it does not require the use of advanced laboratory techniques, which is the case with techniques commonly used to amplify DNA for analysis.
In the PCR test for instance, the RNA of the SARS-CoV-2 virus is first converted into DNA using a process called reverse transcription after which copies of the DNA are made and amplified. RT-PCR tests can take up to nine hours to show results, however, the overall time, from the time that the samples are collected to the report being delivered can take over 24 hours. The PCR test takes longer also because the swab is screened to decide the family of the virus, following which a second test is done to ascertain if the virus is the novel coronavirus.
In April, states in India started looking at “rapid tests” or serological tests as an alternative to the RT-PCR tests amid the growing number of cases in the country. Rapid tests are blood tests, which can be used to identify if the person has been exposed to a particular pathogen. The serological test screens the plasma for antibodies that the body develops against the virus. It takes less than 30 minutes. Even so, the PCR test is able to identify the virus at an earlier stage than serological tests, which checks for antibodies that can take several days to develop. Significantly, the positive serological tests ultimately go through the PCR filter.
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Further, while rapid tests and RT-PCR tests are capable of delivering false negative results, the chances of that happening with the naked eye test are low. “Many of the diagnostic tests currently on the market cannot detect the virus until several days after infection. For this reason, they have a significant rate of false negative results,” Pan was quoted as saying in the press release.
Moreover, because this test does not require laboratory equipment or trained personnel to run the test and analyse the results, it could be far less expensive than the other tests available in the market. Even so, the researchers say more clinical studies on this test are warranted and the test needs the US Food and Drug Administration’s (FDA) approval before it can be sold in the market.
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