The results are positive for antigen test developers, who have seen demand drop after the vaccine is launched.
A small study funded by the National Institutes of Health (NIS) found that the Covid-19 lateral flow test (LFT) is as effective as the polymerase chain reaction (PCR) test in detecting SARS-CoV-2 infection. It is performed every three days One screening.
PCR tests are considered the gold standard for diagnosing Covid-19 infection, but their widespread use as screening tools is limited because they need to be processed in the laboratory and the results may take several days to reach patients.
In contrast, LFT can provide results in as little as 15 minutes, and users don’t even need to leave home.
Researchers affiliated with the NIH Diagnostic Rapid Acceleration Program reported the results of 43 people infected with Covid-19. Participants were from the University of Illinois at Urbana-Champaign (UIUC) SHIELD Illinois Covid-19 screening program. They either tested positive themselves or were in close contact with people who tested positive.
Participants were admitted within a few days of exposure to the virus, and the test results were negative within 7 days before enrollment.
They all provided saliva samples and two forms of nasal swabs for 14 consecutive days, which were then processed by PCR, LFT, and live virus culture.
Virus culture is a highly labor and cost-intensive process that is not used in routine Covid-19 testing, but helps to highly determine the nature of the virus from the sample. This can help researchers estimate the onset and duration of Covid-19 contagion.
Christopher Brooke, Professor of Molecular and Cell Biology at UIUC, said: “Most tests detect genetic material related to the virus, but this does not mean that there is a live virus. The only way to determine whether there is a live, infectious virus is to perform Infectivity determination or culture.”
Then, the researchers compared three Covid-19 virus detection methods-PCR detection of saliva, PCR detection of nasal samples, and rapid Covid-19 antigen detection of nasal samples.
The saliva sample results are performed by an authorized PCR test based on saliva developed by UIUC, called covidSHIELD, which can produce results after approximately 12 hours. A separate PCR test using the Abbott Alinity device is used to obtain results from nasal swabs.
Rapid antigen detection was performed using Quidel Sofia SARS antigen fluorescence immunoassay, LFT, which is authorized for immediate care and can produce results after 15 minutes.
Then, the researchers calculated the sensitivity of each method in detecting SARS-CoV-2, and also measured the presence of live virus within two weeks of the initial infection.
They found that PCR testing is more sensitive than rapid Covid-19 antigen testing when testing for the virus before the infection period, but pointed out that PCR results may take several days to be returned to the person being tested.
The researchers calculated the test sensitivity based on the test frequency and found that the sensitivity of detecting infection is higher than 98% when the test is performed every three days, whether it is the rapid Covid-19 antigen test or the PCR test.
When they evaluated the detection frequency once a week, the sensitivity of PCR detection for nasal cavity and saliva was still high, about 98%, but the sensitivity of antigen detection dropped to 80%.
The results show that using the rapid Covid-19 antigen test at least twice a week for the Covid-19 test has comparable performance to the PCR test and maximizes the possibility of detecting the infected person in the early stages of the disease.
These results will be welcomed by rapid antigen test developers, who recently reported that the demand for Covid-19 testing has decreased due to the introduction of the vaccine.
Both BD and Quidel’s sales in the latest earnings were lower than analysts’ expectations, and after the demand for Covid-19 testing fell sharply, Abbott lowered its 2021 outlook.
During the pandemic, clinicians disagree on the efficacy of LFT, especially for large-scale testing programs, as they tend to perform poorly in detecting asymptomatic infections.
A study published by the US Centers for Disease Control and Prevention in January showed that Abbott’s rapid instant test BinaxNOW may miss nearly two-thirds of asymptomatic infections.
At the same time, the Innova test used in the UK showed that the sensitivity to symptomatic Covid-19 patients was only 58%, while limited pilot data showed that asymptomatic sensitivity was only 40%.
Post time: Jul-05-2021