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  • Category
    International Relations
  • Published
    25th Jun, 2020

The Indian Council of Medical Research (ICMR) recommended using rapid antigen test kits for diagnosis of Covid-19 in hotspots and healthcare settings in combination with the RT-PCR test.

Context

The Indian Council of Medical Research (ICMR) recommended using rapid antigen test kits for diagnosis of Covid-19 in hotspots and healthcare settings in combination with the RT-PCR test.

About

  • The Standard Q covid-19 Ag detection kit (rapid antigen testkits) is a rapid chromatographic immunoassay for qualitative detection of specific antigens to SARS-CoV-2.
  • It has been developed by SD Biosensor, a South Korea based company, having its manufacturing unit in Manesar, Gurugram, India.
  • The test can be interpreted as positive or negative after 15 minutes of putting the sample into the well by appearance of test and control lines, which can be read with a naked eye, requiring no specialized equipment.
  • Maximum duration for interpreting a positive or negative test is 30 minutes.

What are Antigens?

  • Antigens are substances that cause an immune response in the body by identifying substances in or markers on cells.
  • It is a toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies.
    • Human body produces antibodies to fight antigens, or harmful substances, and tries to eliminate them.

What is real time RT–PCR?

  • Real-Time-Polymerase Chain Reaction Test or Real time RT–PCR is a nuclear-derived method for detecting the presence of specific genetic material in any pathogen, including a virus.
  • Originally, the method used radioactive isotope markers to detect targeted genetic materials, but subsequent refining has led to the replacement of isotopic labelling with special markers, most frequently fluorescent dyes.
  • This technique allows to see the results almost immediately while the process is still ongoing, whereas conventional RT–PCR only provides results at the end of the process.
  • Real time RT–PCR is one of the most widely used laboratory methods for detecting the COVID-19 virus.
  • The causative agent for Covid19 is the SARS-CoV-2 virus. It is an RNA virus, that means it infiltrates a healthy cell to multiply and survive.
    • The SARS-CoV-2 RNA is generally detectable in respiratory specimens during the acute phase of infection.  
    • For that upper and lower respiratory specimens (such as nasal, nasopharyngeal or oropharyngeal swabs, sputum, lower respiratory tract aspirates, bronchoalveolar lavage, and nasopharyngeal wash/aspirate or nasal aspirate) are collected.
    • This sample is treated with several chemical solutions that remove substances, such as proteins and fats, and extracts only the RNA present in the sample. 
  • Thus the RT-PCR test is for the identification of SARS-CoV-2 RNA.
  • In this, the RNA is converted to DNA through a process called 'reverse transcription' for detecting viruses.

Significance of the step  

  • The rapid antigen kits allow faster diagnosis without laboratory examination.
  • Antigen tests directly detect the presence of viral proteins using immunoassay techniques. They require successful swabs and since the tests do not amplify signal like NAATs, the sensitivity is lower.
  • The advantage of antigen tests is that manufacturing such tests are easily scalable. In addition, tests can be run either in a laboratory setting with high throughput analyzers or in a point-of care low throughput setting with rapid lateral flow tests.
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