Kerala’s “over reliance” on antigen tests, which are less sensitive, rather than the gold standard test, RT-PCR, is responsible for the State’s current predicament, a huge majority believes. How factual is this?
“There is a clear distinction between testing a person for clinical diagnosis and testing for public health surveillance. From a public health perspective, one should worry less about test sensitivity and prioritise testing frequency and faster turnaround time. Even the most sensitive RT-PCR test has a sensitivity of only about 70% which means that we are likely to miss 30%,” said T.S. Anish, Associate Professor of Community Medicine, Government Medical College Hospital, Thiruvananthapuram.
Moreover, PCR tests are more resource intensive, require a high turnaround time and are not easily accessible.
Key role
Antigen tests, on the other hand, are point of-care tests which can pick up individuals when they are the most infectious. Thus they have a key role in rapidly identifying those at highest risk for transmitting disease. (Rethinking COVID-19 Test Sensitivity — A Strategy for Containment, M. Mina et.al, NEJM Nov 2020)
“Tests that can quickly identify many individuals with infectious virus (rather than simply viral RNA), including when individuals have no symptoms, could limit the spread of infection and help prevent large outbreaks. Antigen tests have the potential to serve this role,” (November 13, 2020 JAMA). Rapid antigen tests being the villain, is “utter nonsense”, a public health expert said.
