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SalivaDirect: Covid-19 Test

  • 17 Aug 2020
  • 3 min read

Why in News

The USA Food and Drug Administration (FDA) has authorised the emergency use of a new saliva-based laboratory diagnostic test for Covid-19 - ‘SalivaDirect’.

Key Points

  • About SalivaDirect:
    • It is a new rapid diagnostic test for novel coronavirus infection that uses saliva samples. It is simpler, less expensive and less invasive than the traditional method for such testing known as nasopharyngeal (NP) swabbing.
      • NP swab is used to detect upper respiratory tract infections, such as whooping cough and Covid-19. It is used in Polymerase Chain Reaction (PCR) and antigen tests.
      • In this test, secretions from the back of the nose and upper throat are collected using a swab.
      • The secretions are sent to a laboratory where they are grown in order to make it easier to identify which viruses, bacteria or fungi are present.
    • Collecting and testing saliva samples include three steps:
      • Saliva is collected without preservative buffers.
      • It is first treated with proteinase K followed by a heat inactivation step (to remove contamination).
      • It is then directly used as an input in the dualplex RT-qPCR mechanism.
        • In Quantitative Reverse Transcription Polymerase Chain Reaction (RT-qPCR) mechanism, the viral RNA is quantified to detect the novel coronavirus.
        • Coronavirus is made up of Ribonucleic Acid (RNA).
  • Benefits:
    • High Sensitivity: The sensitivity is about 93%. SalivaDirect test can detect when the number of virus copies in the saliva sample is as low as 6-12 copies per microlitre.
    • Non-Invasive: It uses saliva, instead of relying on nasopharyngeal (nasal) specimens, which makes the sample collection non-invasive.
    • Protects Healthcare Workers: Collecting the sample from the nasopharyngeal region requires a swab to be inserted into the back of the nostrils, which very often causes irritation leading to sneezing and coughing, thus exposing healthcare workers from getting exposed to the virus.
    • Large-scale Testing:
      • Saliva samples are a viable alternative to nasopharyngeal swabs and could allow for at-home, self-administered sample collection for accurate large-scale SARS-CoV-2 testing.
      • Further, collecting nasopharyngeal samples can be uncomfortable to people, discouraging them from getting tested. The saliva test is likely to increase testing compliance.

Source: TH

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