If speed, low cost and constraints of molecular testing capacity are the reasons why many States have embraced rapid antigen testing, the test has low sensitivity. Yale University’s saliva test, which was granted emergency use authorisation by FDA, is a rapid, inexpensive, non-invasive and highly sensitive test. India will gain much by adopting the saliva test in lieu of the rapid antigen test.
On August 15, six-a-half months after the first novel coronavirus case was reported in the country, India crossed another grim milestone — 50,000 deaths. The daily death toll reported has also increased in the last 10 days with over 900 deaths on most days. The total number of cases reported as on August 15 stood at nearly 2.6 million; India has been reporting the most daily fresh cases in the world since August 2.
More than the total death toll, which is currently 51,925 as on August 17, what is indeed troubling is the shorter time taken for the death toll to double. The death toll crossed 25,000 on July 16 and doubled to over 50,000 in just 30 days.
Under-reporting of deaths
It is certain that there is some extent of under-reporting of deaths across the country, especially when deaths have occurred outside the health-care system. For instance, reporting of coronavirus cases and deaths by States such as Gujarat and Telangana have been suspect right from the beginning; the pandemic-defying trend seen in these States is in stark contrast to the rest of the country.
No single or combination of factors can explain the low mortality in Gujarat (2,800) and Telangana (703) as on August 17. In fact, in the last one month, the death toll on any single day in Telangana has never crossed 15 and has been in single digits on many days and even reported zero deaths on July 26, while in Gujarat deaths have never crossed 30, except on one day. However, under-reporting of cases notwithstanding, it is very unlikely to be huge to change the death toll to a few-fold.
Like in most southeast Asian countries, deaths per million population has been low in India. While the case fatality rate too has been low in India, the continuous dip in the rate might be due to more cases, including asymptomatic, being detected due to increased testing with rapid antigen tests. Also, large cities that witnessed strained health-care infrastructure due to the surge in cases, leading to more deaths, seem to have passed the peak.
Shortcoming of rapid antigen test
A big shortcoming of rapid antigen tests is its low sensitivity, and despite ICMR’s recommendation, most States have very low rates of validation of negative test results using the molecular method. Relying hugely on rapid antigen tests, even while under-utilising the molecular testing capacity in some cases, will result in many infected people continuing to spread the virus in the community. In a welcome contrast, Tamil Nadu has been testing all its samples using the molecular method.
Advantages of saliva test
If speed, low cost and constraints of molecular testing capacity are the reasons why many States have embraced rapid antigen testing, the emergency use authorisation granted recently by FDA for a saliva test developed by Yale University in the U.S. should be good news for India.
The rapid, inexpensive, non-invasive and highly sensitive test that relies on saliva samples will not only help detect more cases but also reduce the need for trained health-care workers to collect samples. With the testing protocol made freely available, India should facilitate rapid adoption of the tests by States, probably after local validation.
Early results of saliva test have been encouraging and India will hugely gain by embracing it in lieu of the unreliable rapid antigen test, particularly when the virus spreads to rural areas.
Science Chronicle 