Fill in the gap: Test

Written by Shailaja Chandra
, N K Ganguly

Published: April 9, 2020 12:26:30 am

Some countries test as many people as possible; others test those who develop serious symptoms of the infection. (File Photo/Representational)

The nation-wide lockdown that began on March 25 has helped to contain the spread of COVID-19. In its absence, the incidence of infections could have doubled each day, instead of every four days. The responses from public health networks, clinical experts, state governments and district administrations have surpassed expectations. However, it needs to be asked if India’s response to the coronavirus outbreak has any unseen gaps.

Missing in these deliberations on testing are infectious disease specialists. These specialists are available in India, many of them have trained abroad or at AIIMS, CMC Vellore and PGI Chandigarh, but they mostly work in big private hospitals. The Clinical Infectious Diseases Society (CIDS) and the Indian Association of Medical Microbiologists (IAMM), the National Academy of Medical Sciences and the National Academy of Sciences are not known to have proffered any advice to the government. If they are waiting to be invited to the high table, no time should be lost in extending the invitation!

The National Institute of Biologicals (NIB) was established in 1992 by the Ministry of Health to function as the apex body and was mandated to ensure validation of invitro diagnostics, vaccines and biotherapeutics, including therapeutic monoclonal antibodies, in the event of a pandemic. The NIB is similar to the North American Background Screening Consortium (NABSC) and the FDA’s Center for Biologics Evaluation and Research (CBER), which validates assays and tests. The NIB ought to deliver on its mandate and the best infectious diseases professional in the country should be steering it. A search committee of retired virologists, infectious diseases specialists and medical microbiologists should be constituted urgently to find a director for the NIB.

That apart, it is important to understand what different tests can and cannot do. Traditionally, there are two types of diagnostic tests for infectious organisms — tests for the presence of the virus itself (current infection), and tests for antibodies to the virus (current or prior infection). The PCR test used for detecting specific genetic material of a virus is key to determine if someone ill is infected with COVID-19. The test uses swabs from the nose and throat and has a high accuracy rate. The WHO and US FDA recommendations have also added antibody and antigen tests alongside the PCR. This will enable mass screenings — these have to be confirmed by PCR tests.

Some countries test as many people as possible; others test those who develop serious symptoms of the infection. The decision is dependent on infrastructure and logistics available. It is difficult to have PCR testing for large proportions of the population. Some countries like Germany are investigating the use of serology results as an “immunity passport”. So far all countries, including South Korea and Italy, have relied on PCR testing.

The PCR test identifies a virus from the swabs taken a few days after infection, to about 8-10 days after the first symptoms appear. Early testing can help to identify and isolate infected people and thereby, limit the spread. It can also provide clues to community transmission, including anticipating the percentage of population that might develop serious complications. It can also tell us which strategies have worked in controlling the spread of the disease — for instance, whether market and school closures made a difference.

A PCR test takes six to eight hours, not counting the time taken to collect and send the sample to the nearest lab. It is expensive — each test costs around Rs 4,500. A commercial test named X-pert has recently been approved by the US FDA for detecting the virus’ nucleic acid (genetic information) within a couple of hours. A similar test is available in India for diagnosing TB. When reagents are available, this test can be used on multiple TB-testing machines, at least in the interregnum.

The antibody test is the best to calculate the number of people who may have experienced COVID-19, either symptomatically or asymptomatically. It is dependable for hotspot surveillance; it is quick and helps to see who has been infected more than 10 days earlier. The only negative aspect of it is that if conducted very early, it may miss virus shedders while hunting for the antibodies. The third test — the antigen test — identifies the protein component of the virus and could be used even sooner than the antibody test.

Some say that the best test for an early infection is combining the antibody test and the PCR test on swab because by itself the PCR test is reported to have only a 66 per cent detection rate in the first week, and the antibody test has only a 38 per cent detection rate, even if the person has been sick for a few days.

It is not possible to conclude which is the best test because COVID-19 is a new challenge for mankind. One does not know yet if antibodies which may be present will protect people against re-infection. Clearly, a dedicated institution with experts who can give undivided attention to testing in conjunction with the National Centres for Disease Control (NCDC), needs to be set up. The NCDC also has to be strengthened. The NIB should be revitalised, and given the autonomy to guide testing under the best possible infectious disease specialists available in the country. We need testing protocols, networks and interpretation of data so that India is ready in the event of any outbreak in the future.

Chandra is former chief secretary, Delhi and secretary, Ministry of Health and Family Welfare, and Ganguly is former director general, Indian Council of Medical Research. With inputs from Arunaloke Chakrabarty, head of microbiology at PGI, Chandigarh, and Gagandeep Kang, executive director of THSTI

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