India has allowed faster and cheaper antibody tests which are also being referred to as rapid tests to detect coronavirus disease in hot spots--about 20 clusters of infections in the country currently and 22 others with the potential to turn into one. This will not only increase the overall testing capacity and cut costs but will also lead to quicker response to aid containment efforts. The antibody tests or rapid tests do not require testing a throat or a nasal swab from a suspected patient and are done by testing a patients’ blood sample, serum or plasma using simpler testing kits. Here are some important facts about rapid testing.
1. The test process in use till now is called PCR or polymerase chain reaction which identifies the Sars-CoV-2 virus from the throat or nasal swab samples of suspected patients. The PCR test results can take up to five hours while the antibody test results will be available in 15-30 minutes.
2. The antibody test will test blood samples of people in the hotspots to see how many have been infected including those with mild or no symptoms. This is crucial to assess the percentage of infected people who have managed to defeat the virus without significant medical intervention. Such people could also be referred to as “corona-blockers”.
3. Those who test positive in rapid test or antibody test will be tested for confirmation through RT-PCR (reverse transcription-PCR) using throat or nasal swab. This means positive results will be reconfirmed using the PCR test.
4. Now let’s understand how the rapid test works- The antibody test uses a blood sample to detect antibodies against coronavirus in a person’s immune system. Presence of coronavirus antibodies would establish that the person was either infected in the near past or is infected currently.
{{/usCountry}}4. Now let’s understand how the rapid test works- The antibody test uses a blood sample to detect antibodies against coronavirus in a person’s immune system. Presence of coronavirus antibodies would establish that the person was either infected in the near past or is infected currently.
{{/usCountry}}5. Antibody test or the rapid tests are part of the standard testing protocol for several infections including dengue and chikungunya and the Indian testing laboratories have sufficient understanding and experience of carrying out these tests. On top of it, these testing kits can be produced on a mass scale in a relatively shorter span of time.
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6. Rapid testing kits to be used are being approved by the Indian Council of Medical Research (ICMR). These rapid tests are relatively simple to perform and interpret and therefore require limited test operator training. They may be intended either for use in hospital laboratories or near the point-of-care.
7. There are two types of Covid-19 rapid tests currently in use globally or in development- direct SARS-CoV-2 antigen detection and indirect antibody detection tests. Antigen detection tests detect viral components present during the infection in samples like nasopharyngeal secretions but results from these tests have sometimes taken up to two days to reach the point of care, therefore, the antibody test, which detects the antibodies that later appear in serum/blood/plasma as part of the immune response against the virus, are being added to the testing mix for quicker detection and response.
8. It must be noted that SARS-CoV-2 antibody detection tests have a limitation and are unable to detect Covid-19 in cases of recent infections as it can take up to 10 days or more after symptoms emerge for a detectable level of antibodies to build up in the patient. The rapid test can often be positive in a patient who has no symptoms of the disease since the antibodies stay in the blood long after the infection has cleared.
9. Rapid tests are also considered to be less accurate and less sensitive than laboratory-performed diagnostic tests such as PCR, therefore, clinical validation is recommended.
10. The rapid test detects IgM and IgG antibodies to SARS-CoV-2 in whole blood, serum or plasma samples that bind to the virus antigen present in the testing kit.