Antigen tests not fully reliable to detect coronavirus: Experts

The concept of antibody tests using rapid testing kits was rejected in TN in April because of non-efficacy and low accuracy in the testing strategy. Experts say the accuracy of antigen tests can be less than 50%. "The antigen test has been initiated in Delhi and can be used to check if people were exposed to the virus. Once an individual is exposed, they are likely to develop antibodies and would indicate IgM presence in the antigen test. However, an antigen test cannot be an indicator of the presence of the virus. The RT-PCR is the standard test for that. The antigen tests can be only used for monitoring and check eligibility of the person for plasma donations," said Dr Vivek Dixit, senior research scientist at AIIMS.

Experts also said that false negative results are very likely in frontline workers and positive results would only indicate exposure to the virus. "The positive results would indicate exposure to the virus in the recent past or recovery due to the presence of antibodies. However, negative results are about 60-70% false negative cases," said Dr Sivakumar, chief of medicine at Villupuram Government Medical College and Hospital.

However, public health experts and virologists also say that antigen testing can be futile if the right amount of virus particles are not tested. Deputy director of National Institute of Epidemiology Dr Prabhdeep Kaur said there is a wide variation among antigen testing kits. "The antigen test is not necessary for people of Tamil Nadu in general. However, RT-PCR tests are mandatory for confirmation to check if an individual is infected," she said.