ELISA Antibody Kits

• 15 May 2020

Why in News

Recently, the Indian Council of Medical Research (ICMR) has approved the first batch of antibody testing kits called “Covid KAVACH ELISA” manufactured by Zydus-Cadila to be used in sero-survey.

Key Points

• Covid KAVACH ELISA has been developed at the National Institute of Virology, Pune, by isolating the virus from patients in India.
  
  • Enzyme-Linked Immunosorbent Assay (ELISA) is a test that detects and measures antibodies in blood.
  • The test can be used to determine antibodies related to certain infectious conditions.
  • It can be used to diagnose HIV, which causes AIDS, Zika virus etc.
• The ELISA kits will be used in the new nationwide “sero-survey” of the Ministry of Health.
  
  • Sero-survey is meant to detect the prevalence of antibodies that appear after a patient has recovered.
  • The ICMR will lead the testing of 24,000 individuals in 69 districts at household level as part of this sero-survey.
• According to the ICMR, real-time Reverse Transcription Polymerase Chain Reaction (RT-PCR) is still the frontline test for clinical diagnosis of Covid-19, but the antibody tests are critical for surveillance to understand the proportion of population exposed to infection.
  
  • The antibody test for Covid-19 acts as a screening process that gives quick results in a few hours.
  • The antibody test detects the body’s response to the virus. It gives an indication that a person has been exposed to the virus.
  • If the test is positive, the swab is collected and an Ribonucleic Acid (RNA) test is done using the Polymerase Chain Reaction (PCR) kit.
• ELISA antibody tests are different from the rapid antibody tests previously used by Indian authorities.
  
  • ELISA kits are more reliable and cheaper than rapid antibody testing kits.
  • The ELISA kit has a sensitivity of 98.7% and a specificity of 100%.
    
    • Sensitivity signifies accurate positive test results, whereas specificity signifies accurate negative test results.
  • According to the World Health Organisation (WHO) the kits are suitable for “for testing large numbers of samples per day, as well as in blood banks or for surveillance studies”.
• ELISA has minimal biosafety and biosecurity requirements as compared to the real-time RT-PCR test.
• Moreover, ELISA-based testing is easily possible even at the district level as the test kit has inactivated virus.

Antibody

• Antibody, also called immunoglobulin is a protective protein produced by the immune system in response to the presence of a foreign substance, called an antigen.
  
  • A wide range of substances are regarded by the body as antigens, including disease-causing organisms and toxic materials.
• Antibodies recognize and attack onto antigens in order to remove them from the body.

PCR Test

• Kary Mullis, the American biochemist invented the PCR technique. He was awarded the Nobel Prize for Chemistry in 1993.
• Under this, copies of a segment of DNA (deoxyribonucleic acid) are created using an enzyme called Polymerase.
  
  • The ‘chain reaction’ signifies how the DNA fragments are copied, exponentially — one is copied into two, the two are copied into four, and so on.
• A fluorescent DNA binding dye called the “probe” is added to DNA, which shows the presence of the virus on a fluorometer.
• However, coronavirus is made of RNA (ribonucleic acid).
• Therefore to detect coronavirus, RNA is converted into DNA using a technique called reverse transcription.
  
  • A ‘reverse transcriptase’ enzyme converts the RNA into DNA.
• Copies of the DNA are then made and amplified.
• Generally, the entire process of PCR test takes 24 hours to deliver the result.

Indian Council of Medical Research

• Indian Council of Medical Research (ICMR) is the apex body in India for the formulation, coordination and promotion of biomedical research.
• Its mandate is to conduct, coordinate and implement medical research for the benefit of the Society; translating medical innovations into products/processes and introducing them into the public health system.
• It is funded by the Government of India through the Department of Health Research, Ministry of Health & Family Welfare.

Source: IE