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RT-PCR tests: What it is and how it is done?

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RT-PCR tests: What it is and how it is done?

What to study?

For Prelims and Mains: RT- PCR tests- procedure, significance and challenges, comparison with other relevant tests.

Context: Bombay High Court has said all frontline workers, including those who are asymptomatic, in hospitals and containment zones in Vidarbha shall be entitled to be tested for COVID-19 using RT-PCR (Rapid Antibody and Reverse Transcription Polymerase Chain Reaction) method.

What happened?

It was announced based on a public interest litigation (PIL) seeking these tests on medical staff, police personnel and others working with COVID-19 patients.

Need for:

Frontline workers, including doctors, nurses, police personnel, and sanitation workers are performing a “herculean” task by putting their lives at risk to protect the lives of others. They are the warriors and soldiers in this process. Therefore, these workers are covered under the definition of suspected cases and hence, should be tested.

How RT-PCR is used for detecting Covid-19? 

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.

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.

How it is carried out?

The SARS-CoV-2 RNA is generally detectable in respiratory specimens during the acute phase of infection.

  1. For that upper and lower respiratory specimens (such as nasal, nasopharyngeal) are collected.
  2. 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. 
  3. Real-time RT-PCR setup usually goes through 35 cycles, which means that by the end of the process, around 35 billion new copies of the sections of viral DNA are created from each strand of the virus present in the sample.
  4. As new copies of the viral DNA sections are built, the marker labels attach to the DNA strands and then release a fluorescent dye, which is measured by the machine’s computer and presented in real-time on the screen. The computer tracks the amount of fluorescence in the sample after each cycle. When the amount goes over a certain level of fluorescence, this confirms that the virus is present. 


Prelims Link:

  1. Difference between RNA and DNA.
  2. Differences between RT PCR and antibody tests.
  3. What is a RNA virus? How it survives?
  4. What are antibodies?

Mains Link:

Discuss the significance of RT- PCR test.

Sources: the Hindu.