Kerala: Antibody tests at airports a waste of time?

THIRUVANANTHAPURAM: The state has begun rapid antibody tests for Covid-19 for those coming from abroad at airports but experts have expressed doubts about the specificity of such tests. A section of medical experts and health campaigners says the chances of obtaining false results are very high in rapid tests, especially for patients with mild or no symptoms.They point out that those testing positive to antibodies -- immunoglobulin M (IgM) or immunoglobulin G (IgG) -- are usually those who have acquired the infection much earlier and they might not be infectious.Dr A Althaf, associate professor, Manjeri medical college hospital said antigen tests have the highest sensitivity as it can detect those within five days of acquiring the infection. “Then comes the RT-PCR tests, which can detect the positives between 5-10 days. Beyond ten days of infection is what the antibody test detects. We cannot claim that antibody tests are foolproof,” he said.An article in the latest issue of British Medical Journal (June 24, 2020) has noted that the existing antibody tests are “so vague that it’s impossible to know how accurate the tests are, especially for people with mild or no symptoms or whose symptoms have gone.’’ “The antibody test will certainly find some people who are positive, but not all. It will also wrongly identify many as false positive or false negative. In Thiruvananthapuram last week, 24 samples tested IgM positive were sent for RT-PCR tests but none of them tested positive in the latter,” a doctor working in government service said.According to internal medicine expert Dr Arun N M, there is no point in conducting RT-PCR tests on those testing positive in the antibody test. “Those testing positive in antibody tests would be infected much earlier and they will not be infectious. There is no point in wasting RT-PCR tests on them again and sending them to Covid hospitals for two weeks and then waiting for two successive negative results,” he said.The sensitivity of kits is also an issue as they have been rated less accurate the world over due to this. “The ICMR has already withdrawn the kits supplied by them due to this. The kits procured by the state government also faced the same issue in quality tests. It will be a big risk judging people as positives and negatives by conducting the antibody tests,” said Dr N Sulphi, vice-president, Indian Medical Association.“What purpose does it serve? The government is anyway planning to send all returnees to quarantine,” said G Pramod Kumar, former advisor with the UNDP. “It’s better to consider all of them as positive and take universal precautions. Think about the mayhem the antibody tests create at airports -- the stress, breach of confidentiality, processes, confusion, hours of wait,” he added.