In wake of the rising coronavirus cases in the country and the mounting pressure on the laboratories to meet the testing target, the Indian Council of Medical Research (ICMR) approved the first test kit for COVID-19. The approved home-based rapid antigen testing (RAT) kit costs just ₹250 and gives results within 15 minutes.

LEARNING WITH TIME/FROM HOME/WITHOUT CLASSES

 The real-time reverse transcription-polymerase chain reaction or RT-PCR is the ‘gold standard’ frontline test for COVID-19. The RT-PCR test is a method of testing by taking a nasal/throat swab from a patient. It involves extracting ribonucleic acid or RNA, which is the genetic material of the virus. If it shares the same genetic sequence as SARS-CoV-2 virus, then it is deemed positive.

It is primarily based on PCR, a process that repeatedly copies and amplifies the specific genetic fragments of the virus, ensuring that there is enough of a sample to conduct the analysis. Coronaviruses have RNA or ribonucleic acid as their genetic material. However, swabs from patients yield only a tiny quantity of RNA, which is not adequate for the testing process. To overcome this problem, the RNA — a single-strand molecule — is converted into a two-strand DNA using an enzyme. This is known as reverse transcription.

ANTIGEN TESTING

The new antigen tests that have been approved for Covid-19 diagnosis in India give results in 30 minutes. These tests are designed to detect a specific protein in the virus that elicits the body’s immune response. In the case of Covid-19, it is the ‘spike protein’ present on the surface of the coronavirus that facilitates its entry into the human cell. An antigen refers to any toxin in the body that triggers an immune response.

ANTIBODY TESTING/also known as serological tests

Rapid antibody testing involves taking a blood sample from the finger and putting it in a testing template. The blood is then examined for two types of antibodies — IgM antibodies, which appear early in an infection, and IgG antibodies, which are more likely to show up later. This process also detects the quantity of antibodies that are produced by the immune system.

Antibody tests can be useful to carry out surveys to check whether a population has been exposed to the virus. These are currently only being used for research and surveillance purposes. Antibodies are naturally produced by the body’s immune system to fight off infections.