Rapid Antigen Detection Tests might show false COVID results: Doctors

GUWAHATI: Sudden decline in the COVID-19 positivity rate in Assam might be due to false negative results shown in the Rapid Antigen Detection Test (RADT). The State recently conducted more than 3 lakh RADTs with an aim to detect more COVID positive cases and thereby isolate the infected ones to prevent further spread of the virus.

Several doctors at government and private hospitals have observed that many individuals tested negative in the RADTs, are now being hospitalized with severe health complications. The serious patients have now been tested COVID positive after the Reverse Transcription-Polymerase Chain Reaction (RT-PCR) tests were done in them.

"Assam has ramped up RADTs instead of RT-PCR tests in order to capture the positive cases more quickly. RT-PCR tests are more accurate, while RADTs register a high rate of false negatives. The RADTs can register as many as 50% 'false negatives' — i.e. samples of those who are actually infected by COVID-19 wrongly returning a negative result. RT-PCR is more accurate," a senior doctor at a leading private hospital said. He said his hospital is now receiving critical patients who were tested as COVID negative recently by RADT.

The doctor said even though the Indian Council of Medical Research (ICMR) has directed that those tested as negative by RADT should be re-tested using RT-PCR, the State has gone slow in implementing the ICMR directive. "Under such circumstances many patients remain unaware of the fact that they are actually COVID positive and shown false negative by RADTs. So, they are developing health complications," a doctor at a government hospital said.

The COVID positivity rate in the State which kept fluctuating in between 6 and 7 per cent till middle of September, has suddenly dipped to 2 to 3 per cent. The positivity rate started declining after the State conducted a special drive and conducted more than RADTs from September 28 to 30. Majority of those tested negative by RADTs during the special drive were not re-tested by RT-PCR, a source in the Health department said.