COVID-19: India needs to ramp up testing but shouldn’t over-rely on rapid antigen tests

India coronavirus burden

With over 60,000 daily fresh cases, India has been reporting the highest numbers in the world for the last few days. Yet, the high test positivity rate strongly suggests that more infected people remain undetected. Chennai is witnessing fewer than 1,000 daily cases, mainly due to aggressive testing and renewed contact tracing.

The extended lockdown might have slowed down the spread of the novel coronavirus in India in the beginning, but in the absence of large-scale testing, tracing and isolation of the infected and their contacts, the virus has been spreading with renewed vitality.

Shorter doubling time

If it took 168 days to reach one million cases on July 16, it took just 21 days to double to two million on August 6; deaths too increased from 25,599 on July 16 to 41,641 on August 6. In recent weeks, the number of daily new cases reported across India has been increasing. Similarly, the number of deaths per day has also been rising; it crossed the 1,000-mark on August 9.

Rise in daily fresh cases

Till mid-July, the daily fresh cases reported were well under 35,000 but increased to over 50,000 since July 29 and have been staying above 60,000 since August 6. Since August 3, India has been reporting the most cases in the world, surpassing the U.S. That the seven-day average test positivity rate is 9.4% underscores the large number of infected people and the compulsion to increase the tests carried out each day. The low daily testing numbers are also reflected in low tests (over 14,000) per million population.

Over-reliance on rapid antigen tests

After Delhi, many States ,including Karnataka, Andhra Pradesh, Uttar Pradesh, and Maharashtra, have increased the number of rapid antigen tests done each day. Indeed, Amit Shah and ICMR wanted States to conduct more rapid antigen tests.

Antigen based test is a rapid point-of-care test and could help in quickly determining an ongoing infection but has low sensitivity. The low sensitivity of the test might help in reducing the test positivity rate, as seen in Delhi, but may not actually help in containment. Particularly so when there is an over-reliance on rapid antigen tests and negative results from them are not validated with the molecular test. ICMR’s first  recommendion on rapid antigen tests on June 14 and again on June 23 unequivocally said that rapid antigen test should be used in combination with RT-PCR tests and all negative results from antigen tests should be validated with RT-PCR. According to Balram Bhargava, ICMR Director-General, rapid antigen tests comprise 25-30% of all tests as on August 4.

Insufficient data

If the ICMR shares only the data on the number of tests done each day, neither the States nor the Health Ministry provide a break-up of different tests and the number of positive results through each method, making the data not very useful.

Though Kerala has reported only over 35,500 cases so far, the compulsion to ramp up testing cannot be overemphasised, particularly in districts where community transmission has been documented. Andhra Pradesh (over 2,35,525) and Karnataka (1,78,087), which initially appeared to have contained the spread, have the third and fourth highest number of cases, respectively, in India.

Absent contact tracing

Aggressive testing through fever clinics in Chennai helped halve the number of daily fresh cases to 1,100-1,200, and further reduction became possible in the last few days. The renewed commitment to trace contacts, including non-family members, in Chennai since July has helped in knocking down the numbers to below 1,000. After putting up a good show initially, contact tracing has been nearly absent since mid-May in Tamil Nadu, Andhra Pradesh and Karnataka, one of the reasons why cases spiked and spread.

After the mega cities, a spike is now seen in the smaller cities in Tamil Nadu, Andhra Pradesh, Karnataka and Maharashtra. The daily confirmed cases and deaths in Gujarat and Telangana during the pandemic give an impression that the States’ priority is to manage the data. This does not augur well for India.

Published in The Hindu on August 11, 2020