Covid-19 testing: What are the different types of tests being used in India for Covid-19 detection?

World Health Organisation’s advice on strategy to deal with Covid-19 pandemic is Test, isolate and trace. Although India has been conducting around 3 lakh tests daily, India’s tests per million continue to be among the lowest in the world, because of the huge population of over 1.3 billion.

According to Factly, India is using multiple types of tests to detect Covid-19. Even though reverse transcription-polymerase chain reaction (RT-PCR) remains the gold standard of covid-19 testing, the government gradually introduced a range of other testing modalities.

Here are the types of  Covid-19 tests in India

RT-PCR test

RT-PCR Test implies ‘Reverse Transcription – Polymerase Chain Reaction’ test. It requires nasal and throat swabs and are used to directly detect the presence of the virus rather than antibodies. The price for the test is between Rs 2,200 and Rs 3,000.

Process: A sample is collected from deep inside your nose and the back of your throat with a swab. The sample is treated with chemical solutions that remove proteins and fats, leaving only RNA present in the sample.

The sample is sent to the laboratory for analysis, where a RT-PCR machine is used to detect the virus. The average time taken is around 4-5 hours from receipt of the sample to getting the result.

Rapid Antibody tests

The antibody tests require a blood sample to determine whether the human body has antibodies for coronavirus. Antibodies are proteins produced by a human body and used by the immune system to identify and neutralise foreign objects such as bacteria and viruses. The test costs between Rs 500 and Rs 600.

Process: The test 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.

TrueNat tests

These tests are commonly used for detection of Tuberculosis and HIV. TrueNat is developed by an Indian firm MolBio Diagnostics’ Pvt ltd. The working principle of the test is same as that of RT-PCR but uses a smaller kit. The tests costs around Rs 1,300

Process: A TrueNat machine is chip-based, small and portable, and mostly runs on batteries. It detects the virus in nasal or oral swabs. In the first step, which is an E-gene screening assay, all samples of suspect cases are tested. All negatives are considered as True Negative. All positives are subjected to second step of the assay. It is equipped to detect RdRp enzyme found in the RNA of the virus. All the samples tested positive are considered as True-positive.

Rapid Antigen detection tests

The test detects the virus rather than the antibodies produced by the body. An antigen refers to any toxin in the body that triggers an immune response.

Standard Q COVID-19 Ag detection kit developed by SD Biosensor, a South Korea based company is approved by ICMR. The company has a manufacturing unit in Manesar, Gurugram, India. The test costs around Rs 450.

Process: Only a Nasal swab is collected, which is then immersed and squeezed into the viral extraction buffer. This buffer inactivates the virus and mitigates bio safety concerns. The sample is then placed in a well of test strip. It takes around 15 minutes to interpret positive or negative result.  It is a point-of-care test that is performed outside the conventional laboratory setting, and is used to quickly obtain a diagnostic result.