ICMR’S guidelines push antigen tests amid surge
The Indian Council of Medical Research (ICMR) on Tuesday issued a fresh Covid-19 testing advisory that recommends using more rapid antigen tests (RAT) in the wake of exponential surge in cases that has overwhelmed the country’s health care delivery system, and caused huge backlogs in the gold-standard RT-PCR tests. While ICMR is counting on more reliable new-generation RAT kits, if the tests end up being as inaccurate as the previous generation of RATS, they could artificially lower Covid-19 case numbers, and potentially create undiagnosed superspreaders.
“The best public health action is to help people know about their status at the earliest, even if somebody is asymptomatic; and laboratories performing reverse transcription polymerase chain reaction (RT-PCR) tests are functioning to their full capacity. So, why should one wait for two to three days to get their confirmatory test result to come back?” asked Dr Samiran Panda, head, epidemiology and communicable disease, ICMR.
To be sure, ICMR’S decision seems to be driven by two factors: new-generation RATS that are more accurate; and the fact that their use has always been recommended when time is a constraint (and in the current context, it is). If time is not a constraint, the use of RT-PCR tests is
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recommended because RATS tend to have a high proportion of false negatives, identifying infected people as uninfected. During the first wave, many states depended on RATS when they were constrained by testing capacity (not time), which is not recommended.
“The companies try to come up with modified kits that are of higher sensitivity and specificity. The current RAT kits that have been evaluated by us, these have been tested to see how they perform in symptomatic individuals and asymptomatic individuals. And we found out that newer kits have improved sensitivity and specificity which means better performance than the earlier ones,” Dr Panda added.
Much depends on the reliability of the tests, an expert said. “If they are so confident about the RAT kits that they have tested then they should have first published the data that’s peer-reviewed, as it would build confidence in people. It should be quality data and out in public domain,” said Jugal Kishore, head, community medicine, Saf24 darjung Hopsital.
Indeed, if the new tests are not accurate, then it could end up identifying a lot of infected people as uninfected, resulting in more infections from those who come in contact with them; it could also make local administrations complacent and overall Covid-19 numbers unrepresentative by showing fewer cases than there really are.
So far, ICMR has approved 36 RAT kits. It has also advised setting up of dedicated 24x7 RAT booths at multiple locations in cities towns and villages. States have also been asked to set up drive-through RAT testing facilities. The idea of the new protocol, different from the previous one which emphasised at least 70% of testing in any region to be RT-PCR (a message consistently reinforced by the health ministry and the PM) is to break the chain of transmission through early diagnosis, Dr Panda said.
There are close to 2,500 RT-PCR testing labs with a testing capacity of about 1.5 million tests a day. Given the surging second wave of Covid-19, the country’s daily testing is in excess of 1.5 million, which means all labs are testing to their capacity.the advisory has done away with the need for RT-PCR test in healthy individuals undertaking inter-state domestic travel, to reduce the load on labs.
It also said that RT-PCR tests must not be repeated in any individual who has tested positive once either by RAT or RT-PCR.
THE STRATEGY COULD LOWER COVID-19 CASE NUMBERS, AND POTENTIALLY CREATE UNDIAGNOSED SUPERSPREADERS