The statement by Director, NEIGRIHMS, P Bhattacharya, that the Rapid Antigen Test (RAT) carried out by the Government of Meghalaya at Byrnihat and other entry points to Meghalaya is a waste of resources that could have been used for PPE or other utilities, makes perfect sense. Bhattacharya said that a person who enters Meghalaya and is tested RAT negative might be carrying the virus but have antibodies at the time of testing which will not show up instantly. But why did this piece of wisdom take so long to emerge? Last month the Union Health Ministry had directed all states and Union Territories to mandatorily retest all symptomatic negative cases of RATs with RT-PCR. The ministry had noted that symptomatic cases tested negative by RATs are not followed up by RT-PCR testing in some large states. Hence the Ministry insisted on RT-PCR confirmatory tests so that no positive COVID-19 cases are missed.
Labelling RATs as spuriously comforting, immunologist from the National Institute of Immunology (NII) Satyajit Rath said it is also known that there are false negative outcomes in the tests. The Indian Council of Medical Research knew this all along and advised RAT-negative symptomatic people to be re-tested with RT-PCR tests. Rapid antigen tests (RATs) for Covid-19 are cheaper and deliver quicker results but should be no more than an adjunct to the more reliable RT-PCR tests because of the potential for false negative results, scientists across the world warn. Virologists have been reiterating that RATs have a field sensitivity of 50-60 per cent and show many false negatives. Hence if a person has symptoms despite testing RATs negative he/she should be retested.
Experts have also noted that while rapid antigen tests detect viral protein, the RT-PCR tests detect viral RNA or its genetic material. RT-PCR tests ‘amplify’ viral RNA while detecting it, but antigen tests do not do any such amplification of the detected viral protein. Because of this amplification step, RT-PCR tests for viral RNA are more sensitive than antigen tests. Fact is that there are not enough RT-PCR test centres in Meghalaya and the results take a long time in specialised centres. So the RAT is being used for instant testing but with a somewhat spuriously comforting rationale. Scientists now say there are far less expensive and cumbersome ways of detecting viral RNA than RT-PCR without losing the sensitivity advantage, but very few companies are making those kits. Even the biotech companies in India have not yet seen this critical gap and have not filled it.
Meghalaya has spent a substantial amount on Corona care which includes free testing. If the RAT was a waste of resources, could this not have been pointed out earlier? NEIGRIHMS, IIPH Shillong and the State Health Department could have worked in tandem for better results. A cautionary tale that comes after the fact is a postscript.