Antigen testing detects SARS-CoV-2 better than PCR

A team of U.S. scientists say that rapid antigen testing for Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) will determine the actual infection status of patients with coronavirus disease 2019 (COVID-19) more than they really are. Shows that it is effective for. Time polymerase chain reaction (RT PCR) based test. Research is currently medRxiv* Preprint server.

SARS-CoV-2, the pathogen responsible for the COVID-19 pandemic, is a single-stranded RNA virus that spreads rapidly from person to person, primarily via respiratory droplets. The average incubation period of the virus is 5.8 days and can be extended up to 14 days. Studies show that viral RNA can be detected by the polymerase chain reaction (PCR), but about eight days after the onset of symptoms, no infectious virus (live virus) remains in the patient’s specimen.

For the detection of SARS-CoV-2, the US Food and Drug Administration (FDA) recently approved an antigen-based test for the rapid diagnosis of COVID-19. These tests are immunoassays that directly detect the presence of a target viral protein (antigen) in a biological sample. There is evidence that antigen-based test results correlate better with culture-based test results compared to PCR-based test results.

Current research purpose

Given the importance of antigen-based testing in the definition of infectivity, the current study is aimed at evaluation. Effectiveness of An antigen-based SARS-CoV-2 test to distinguish between infectious and non-communicable individuals compared to PCR-based tests.

Current research design

Scientists performed both PCR-based and antigen-based tests using respiratory swab samples from different regions throughout the United States. The results were compared to the SARS-CoV-2TMPRSS2 culture, a sensitive virus culture test used as a reference method to determine infectivity.

Important findings

In virus culture tests, of the 38 PCR-derived positive samples, 28 were positive and 10 were negative. By comparing antigen-based test results, scientists observe that all but one sample is positive in both PCR-based and culture-based tests, and is also positive in antigen-based tests. Did. Of the 10 samples that were positive in PCR but negative in virus cultures, 2 were positive in antigen-based tests. These findings indicate that antigen-based test results correlate better with virus culture results.

In addition, scientists found that out of 38 PCR-positive samples, 9 were negative on antigen-based tests. Viral RNA loading was significantly lower in these 9 samples compared to the other samples. By comparing the viral RNA load to the test type, scientists observed that there was no difference between the antigen test and the viral culture in providing positive results. However, the PCR test gave positive results with a much lower RNA load, with minimal similarity to viral cultures.

Regarding the efficacy of the test, the antigen test showed 96% sensitivity and 98% specificity, while the PCR test showed 100% sensitivity and 95% specificity. Antigen and PCR tests showed positive predictions of 90% and 73%, respectively, with a study prevalence of 11% determined by virus culture positive results (251 samples total).

Importance of current research

Current research results show that both antigen and PCR tests have about the same sensitivity in detecting SARS-CoV-2 over a period of less than 8 days after the onset of symptoms. However, like the virus culture test, the antigen test is better at detecting the presence of infectious virus in a patient’s sample than a PCR-based test. Even after the infectious virus has been completely attenuated, PCR testing can still detect viral RNA in respiratory swab samples.

Studies have shown that in COVID-19 patients, infectious virus cannot be detected in samples taken from the upper respiratory tract 10 days after the onset of symptoms. Therefore, the chances of getting a virus from these people are very low.

Antigen testing may be more effective in distinguishing between infectious and non-communicable people quickly and in a timely manner, as it has a relatively higher predictive value of positive than PCR tests.

*Important Notices

medRxiv Publish preliminary scientific reports that should not be considered definitive as they are not peer-reviewed, guide clinical / health-related behaviors, and should not be treated as established information.