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Rapid Test

  • 01 Apr 2020

  • In order to tackle suspicions of whether the novel coronavirus has spread into the community and if not prevent such a scenario, the Kerala government recently announced ‘rapid tests’ that will ensure speedy results within half an hour.

About Rapid Test

  • Essentially, a rapid test is conducted to determine whether there has been any kind of recent viral infection in a person’s body.
  • When a pathogen enters a human body, specific antibodies are released as a response to the virus.
  • A rapid test can detect the presence of such antibodies in blood, serum or plasma samples quickly, indicating a viral infection.
  • Rapid testing is conducted usually to check for community transmission of a virus during an epidemic.

Indian Council of Medical Research Guidelines Regarding Rapid Test

  • The ICMR guidelines released on March 28th, 2020, clearly say the rapid antibody kits are not recommended for diagnosis of coronavirus infection.
  • It can only be a preliminary screening test. Positive test indicates exposure to SARS-CoV-2. Negative test does not rule out Covid-19 infection.
  • The person still has to be subjected to the polymerase chain reaction (PCR) test for confirmation of the SARS-CoV-2 virus.

Advantages of Rapid Test

  • It will help screen more people in a mass way on a daily basis and is much cheaper than the present RT-PCR testing method.
  • Moreover, it can be repeated when a patient is in isolation/quarantine to check IgG AB levels, which can reveal the extent of recovery.

Drawback

  • Even though a rapid test can be extremely helpful to check for community transmission during a global pandemic such as this, it is not a confirmatory test for SARS-CoV-2 that causes the coronavirus infection.

Rapid Test Vs Reverse Transcriptase Polymerase Chain Reaction

  • So far, India has used the reverse transcriptase polymerase chain reaction(RT-PCR ) test on nasal or throat swab samples of suspected patients to test for Covid-19.
  • The PCR test checks for the presence of the virus genetic material in an individual’s blood. However, they can take anywhere between 12-24 hours to show results.
  • In comparison, the rapid antibody tests identify disease-fighting antibodies in blood samples and can deliver results in 45 minutes to two hours.
  • However, since antibodies are usually detectable only after around 7-10 days of being infected by the virus, such tests could throw up false negatives – an infected person may appear normal in the blood test.

Reverse Transcription Polymerase Chain Reaction (RT-PCR)

  • RT-PCR is a laboratory technique combining reverse transcription of RNA into DNA (in this context called complementary DNA or cDNA) and amplification of specific DNA targets using polymerase chain reaction (PCR).
  • It is primarily used to measure the amount of a specific RNA.
  • This is achieved by monitoring the amplification reaction using fluorescence, a technique called real-time PCR or quantitative PCR (qPCR).

Applications

RT-PCR is used in research laboratories to study gene expression, for example in experiments to distinguish exons from introns, and can be used clinically to diagnose genetic diseases and monitor drug therapy.


So, why is Kerala insisting for Rapid Test?

  • According to the Kerala government, while the rapid tests cannot determine if there is an active infection of the coronavirus, it will determine if there has been any viral infection in the recent past.
  • The use of the rapid tests in the community will also be able to help determine if there is any community transmission of the coronavirus disease.
  • It will help to identify those with suspected infection, put them under observation and if required, subject them to the PCR test for coronavirus confirmation.