Rapid antibody test to trace COVID cases

The National Task Force deliberated with experts to ascertain the use of these rapid tests kits, and the draft of the suggested algorithm was also discussed in detail with technical experts from the Health Ministry, said ICMR director general ICMR chief Balram Bhargava in a communication to Union Health Secretary Preeti Sudan.

Till now, India has been using reverse transcriptase polymerase chain reaction (RT-PCR) test, which checks for the virus in the DNA from throat or nasal swab samples from suspected cases. It takes about 12-24 hours for the results to come, which can lead to delays and backlog.

In contrast, the rapid antibody test checks for the presence of antibodies in blood samples, the results of which would be available within a maximum of two hours. The idea is, if a person has had a mild coronavirus infection, the body would have produced an antibody to fight it.

Thus, a person testing positive – showing the presence of the antibody – is an indication that she has been infected. In that case, the RT-PCR test is conducted.

There, however, are risks as well. Antibodies are often found only after a week or so since the infection, due to which there could be false negatives as well. Hence, the ICMR advisory says all persons in clusters other hotspots who have influenza like illnesses (ILI) should be advised home quarantine for 14 days.

According to the advisory, persons with ILI symptoms should be tested using rapid antibody tests. Even if negative, the doctors may either recommend RT-PCR test or repeat the antibody test after 10 days – during which the person should be in home quarantine. If positive (that is, there are antibodies in the body indicating infection), the person should be clinically assessed, treated in hospital or isolation and initiate contact tracing.