India currently uses the molecular assays method of testing
There are two methods of testing available to find out if a person is infected with the novel coronavirus (SARS-CoV-2) or not. These two methods are: Molecular assays and immunoassays.
India currently uses the molecular assays method of testing.
Molecular assays can either be manual or automated. In this method, an oral swab sample is taken. Viral Ribonucleic Acid (RNA) material is isolated from the swab using several chemicals, since the novel coronavirus is an RNA virus.
The amount taken, however, is little, making it impossible to find the pathogen directly from such a sample.
A technique called the polymerase chain reaction technique (PCR) is used to increase the material.
An additional step of treating the sample with an enzyme, called reverse transcriptase, is needed to use the PCR technique.
The RNA is then converted into a complementary strand of Deoxyribonucleic Acid (DNA). This DNA is then usually replicated around 40 times over.
Enzymes and nucleotides, fluorescent probes and other primers — specific to the viral genetic material — are added during the replication process.
The fluorescent probes provide a visual signal and are released from each DNA strand, when replication of the strand is complete.
Replication would occur and the visual signal would be seen if the sample contained the novel coronavirus RNA.
India currently uses imported RT-PCR test kits to carry out testing using this method.
The Indian Council of Medical Research approved two test kits on March 23, 2020 after finding them to be 100 per cent sensitive to true positive and true negative samples.
Immunoassays — also called rapid tests — follow the same principle used in pregnancy tests.
They identify Immunoglobulin M and Immunoglobulin G antibodies developed against the SARS-CoV-2.
Blood, serum and plasma can be used for the test. Antibodies, if present in the sample, bind to the antigen immobilised on the test strip and give a coloured reaction.
These test kits are easy to use, provide quick results and are also effective in identifying asymptomatic patients.
The results from this method, however, need to be confirmed using a more advanced test as there is a risk of getting false positives.
Many such tests are available globally, but not in India.
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