The Indian Council of Medical Research (ICMR) on April 2 issued an interim advisory for the use of rapid antibody tests for COVID-19 in ‘hotspot areas’.
The medical body said, “Population in hotspot areas may be tested using rapid antibody test. And antibody positives to be confirmed by RT-PCR using throat/nasal swab, antibody negatives to be quarantined at home.”
But what are rapid antibody tests?
These tests, also known as serological tests, are blood-based tests that can be used to identify whether people have been exposed to a particular pathogen. These tests are commonly used to screen a person for an HIV infection; it can detect the HIV antibodies in the blood or oral fluid in under 30 minutes.
The US Food and Drug Administration (FDA) had approved the use of five such test kits for COVID-19 on March 20, 2020. “We approve kits that are registered and used in countries with advanced technology and wide experience with COVID-19. We want the people to have access to testing, but of course, proper evaluation and safeguards will still be in place,” FDA Director-General Eric Domingo had said.
He added that these kits will yield a faster result compared to PCR-based kits, but it is important that a trained health professional evaluate and interpret the results.
So how are we currently screening patients for COVID-19?
Currently, the real-time reverse transcription-polymerase chain reaction-based tests (RT-PCR) are the recommended diagnostic tests for COVID-19. These typically involve the use of a nasal or throat swab to test for the presence of the coronavirus’ genomic sequences and take anywhere between 24 to 48 hours to yield results and show whether a person has an active infection or not.
The appeal of rapid antibody tests for COVID-19 and risks involved
These serological tests for COVID-19 are attractive under the current circumstances, especially because of the relatively shorter time involved in diagnosis.
According to a report in the Financial Times, these tests also gain significance in light of the coronavirus outbreak and the lockdown that followed since they could be used to assess who may be immune to the infection and could be allowed to leave lockdown to return to normal life — or to help others, in the case of healthcare workers.
However, the ICMR had earlier said in its March 28 guidelines that these rapid kits can only be a preliminary screening test for the coronavirus infection. This is because these tests only measure the antibodies and not the viral load itself. As a result, there might be cases of false negatives for patients who have indeed been infected as the body takes time to develop antibodies.
“A positive result due to cross-reaction with other bacteria or viruses is also possible, which is why a confirmatory PCR-based test is still required,” FDA Director-General Domingo had said.