COVID-19 test kit: RT-PCR is the diagnostic assay for COVID 19. To better understand the transmission and develop effective measures against it, antigen- and antibody-based immunoassays is essential. We at Oncquest will perform both antibody and antigen tests additionally to RTPCR. Do you know its main advantage? The main advantage is its sensitivity and speed. The PCR limits diagnosis to the acute phase of the infection and requires high-quality specimens. SARS-CoV-2 loads within the tract vary considerably. This may cause high false-negative rates, despite taking multiple swabs. There's also a problem of scale. RTPCR testing requires specialised infrastructure, BSL 2 Labs, highly trained skill force, cost, reagents and far more.
Immunoassays over PCR
Immunoassays show some distinct benefits over PCR. Antibodies and antigens are considerably more durable than RNA and fewer at risk of spoliation during transport & storage, thus reduce the prospect of false-negative results. The very fact additionally improves testing accuracy that antigens and antibodies are more uniformly available in sputum and blood samples. However, the essential advantage of immunoassays is its ability to detect past infections.
What after COVID-19 Recovery?
- Once a patient has recovered from coronavirus, viral RNA is not any longer available for detection, leaving only a brief window during the acute stage of infection, within which SARS-CoV-2 may be detected. While it works for the analysis of ongoing diseases, it does not indicate whether a patient has had the virus within the past and what's their immune status (i.e. if they're proof against COVID-19 or still vulnerable to disease).
- Unlike RNA, antibodies are long-lasting and might move the bloodstream for long, after infection. As such, immunoassays help us to spot patients that have had COVID-19, retrospectively. The sort of antibody, its relative levels could even be accustomed to indicate the stage of infection and estimate time since exposure for contact tracing. However, antibody tests have their limitations too. The body’s antibody response to COVID-19 is slow – considerably slower.
- The initial IgM antibody response doesn't peak until 7-9 days after initial infection and also the IgG antibody response doesn't rise until day 9-11. Thus, antibodies are unlikely to create useful markers of acute COVID-19 disease. The combined RT-PCR/antibody testing can reduce false-negative rates, but the utilization of antibody just for acute-phase diagnosis alone may be a risky strategy.
How are antibodies valuable?
However, antibodies have many valuable applications. By conducting random antibody a sampling of health & industrial workers, office staff, general public etc., health bodies could better estimate verity levels of exposure and develop a better understanding of population immunity and identifying potential geographical ‘hot-spots’. This may help in making the proper public health decisions, for estimating transmission rates, case numbers etc. and allocation of the resources in an exceedingly better manner.
Who Is Eligible for Antigen Testing and Anti Body Testing?
While antibodies aren’t suitable for diagnosing active COVID-19 infections, antigens are likely detectable within the nasal swab from the onset of symptoms. With the employment of Rapid antigen detection (PoC) now it's possible to try and do rapid community screening, and even door-to-door testing has now become a reality. People who suspect infection to induce quick ends up in half-hour and determine whether or not they should isolate and seek medical aid. The most significant advantage of the Rapid Antigen test is scalability and its affordable cost. Also, they are doing not require high skill force, the expensive infrastructure, equipment, and reagents as compared to RTPCR. They will be quickly done on the spot in doctor’s clinics home, daycare centres, hospitals, emergency, industries than on.
Conclusion: The challenge in Rapid Ag test is that they're inherently less sensitive. As a result, most antigen tests have a sensitivity of anywhere between 60% and 90%—in other words, one in two infected people might incorrectly be told they are doing not have the virus. Knowing that SARS-CoV-2 spreads so quickly, and misdiagnosis is worse than no diagnosis.
(With inputs from Dr. Ravi Gaur, Coo and Lab Director, Senior Member FICCI)
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