Testing the limits

In the light of recent surge of positive cases among persons without travel history combined with the urgent need to open up the economy and other activities, a rethinking is certainly required in the strategy.

With three figure surge daily in the last few days among the general population, concerns have been raised as to the current strategy of testing in the state. Are we doing enough? Has the time come to change the strategy?

Till date, a total of 1,58,098 tests has been conducted of which 6,382 has been tested Covid-19 positive. The number of active cases is 1903 of which 714 are from the central paramilitary forces. On the other hand, about 3,46,311 truckers and commuters have been screened at the entry points of the state. The daily testing capacity has been increased in the state and altogether, 10 laboratories, including private ones, are conducting tests using methods as approved by the Indian Council of Medical Research (ICMR).

The testing methods include RT-PCR, TrueNAT and Rapid Antigen tests. The real-time polymerase chain reaction (RT-PCR) test is the most commonly used one for Covid-19. The RT-PCR test starts with a simple swab taken from inside a person’s throat or nose. The time duration for the testing process is around four to eight hours, but results may take up to a day to arrive because of the time taken to transport samples to laboratories. But, the RT-PCR test is also the most expensive of all those used for Covid-19. The cost of the test was capped at Rs 4,500 by the ICMR.

The rapid antigen tests that have been approved for Covid-19 diagnosis in India give results in 30 minutes. For this test, professionals collect a nasal swab, which is then immersed in a solution that deactivates the virus. A few drops of this solution are then put on a test strip. This has to be done within an hour of the immersion of the swab in the solution. If a person is infected with coronavirus, the test lines will appear on the paper strips within 15 minutes. Since antigen testing does not involve any amplification process, swab samples may lack enough antigen material to be detectable.

This may result in false negative tests. For this reason, if a person tests negative through antigen testing, they still need to get an RT-PCR test done for confirmation. If a person tests positive, however, a confirmation RT-PCR is not required. The advantage of using this test is that it reduces the burden of relying on just RT-PCR tests to identify Covid-19 patients. Antigen testing is useful because even if it’s less sensitive, it is rapid and the results that are positive will be positive. So, patients who test positive can get into isolation faster. Also, antigen tests remove about half of the positives from the testing load. Antigen tests are much cheaper than the RT-PCR, and cost Rs 450 each.

As, the ICMR revised its testing guidelines to allow the use of the TrueNAT system for screening and confirmation of Covid-19, it is already available in the state. Unlike traditional RT-PCR tests, the sample preparation in TrueNAT tests is automated, and the results are available within half an hour.

The test uses nose or throat swab samples, which are collected from patients and dipped in a solution that inactivates the virus. The advantage of this test is that it is quick and portable. This allows teams to set up mobile testing centres or kiosks in containment zones, instead of having to transport samples to labs. TrueNAT testing kits are priced at Rs 1,200.

In the light of recent surge of positive cases among persons without travel history combined with the urgent need to open up the economy and other activities, a rethinking is certainly required in the strategy.

Union Health Minister Harsh Vardhan has also opined that States/UTs need to focus on more effective surveillance, adequate testing and timely treatment. We think, the time has come to begin serological survey through antibody tests in clusters where there is concentration of Covid-19 positives. For the antibody test, trained professionals collect a few drops of blood. The positive result is indicated in the form of lines, like a home pregnancy test. It is said, antibody tests can be useful to carry out surveys to check whether a population has been exposed to the virus. So, let us start it.

_Editorial

First Published:Sept. 2, 2020, 7:37 a.m.