Q1. What are the available testing options and which is the best one for diagnosing COVID-19?
There are two broad categories of COVID-19 tests: those that detect the genes or protein in the virus itself, thus identifying people who are currently infected, and those that test for the presence of antibodies, to establish whether a person has been already infected in the past.
For the purpose of diagnosing, only viral testing should be performed. Currently, two main types of tests are available, RT-PCR and Rapid Antigen Tests (RAT). RT-PCR test, considered as the “Gold Standard Test” by WHO, is the most sensitive and specific. Beside these, other testing options in India are TrueNat and CBNAAT, which were already being used for diagnosing TB at the district and primary health centers. However, they contribute to a very small percentage.
Q2. What are the limitations of the diagnostic tests? How reliable are the results?
RT-PCR test has limitations in requiring sample transportation, the requirement of trained manpower, specialized reagents, and equipment, leading to it being more time consuming and costly. RAT test has a major limitation in being moderately sensitive (50-84%), which could lead to missing of mild cases, as they could falsely turn out as negatives.
Positive results are reliable with both of the above tests. However, there could be false negatives, more so with the RAT test. Thus symptomatic persons who turn out negative should follow up with an RT-PCR test to confirm.
Q3. What are Antibody Tests and why are they needed?
Antibody tests are primarily used to determine if a person has already had COVID-19 infection. Antibodies start building up after 5 to 10 days of the start of symptoms. This test is not for the diagnosis of a current infection. It’s for surveillance only, to look for the percentage of the population which has already been exposed and recovered from the infection and for future policymaking.
Q4. Why is testing so important if 80% cases are recovering with mild symptoms?
For COVID-19, a person with mild or no symptoms can also spread the infection. If such people remain untested, they risk exposing others in the family and their surroundings. In the case of clinicians and healthcare workers, they may inadvertently transmit the virus to patients and colleagues, further straining the already precarious health care system. Hence expanded testing is a necessary immediate step toward understanding and resolving this crisis. If this is not done, we would observe a delayed peak, resulting in a prolonged economic crisis, job losses, and further suffering of the weaker sections of the society.
Q5. Where did we go wrong in the initial stages of the epidemic?
Ans. We initially lacked preparedness for COVID testing. An early response on testing, contact tracing, and isolation, could have prevented the spread. When the first few cases were reported in March and lockdown imposed, very few testing laboratories were equipped. It took a few months by the regulatory agency to rope in the academic and private institutes, which were already equipped with the RT-PCR technology, to perform tests. Even now, our testing rate is still quite low. To give a perspective, India is doing 565 tests per million (Aug 16, 2020) in comparison to Australia which is doing 2,887 tests per million.
Q6. What is the importance of open sharing of worldwide testing data?
The pandemic is driven by a novel virus and calls for a global shared approach for its suppression. Data generated from testing is open source and shared globally to generate information on a real-time basis about the percentage of COVID infected people, positivity rate of the tests, and demographic spread of the infection. For example, the testing positivity rate in a particular state informs about the rising/declining trend in the spread. Policy Makers can thus learn from other country’s response and take necessary actions accordingly. For example, mass testing was employed in the Wuhan province of China, and it is almost free of the virus now.
Q7. How can we improve upon our testing strategy?
Considering our huge population size, scaling up of testing is definitely a priority. This would require an increased number of high sensitivity, affordable and rapid kits. Validation of such indigenous kits under the purview of an independent regulatory agency could speed up the process. Also, rapid testing in hot spots, high-risk elderly population and front-line healthcare professionals should be prioritized. In the future, tests similar to the SalivaDirect (developed by NBA and Yale, US), which can be performed using Saliva, could be game-changing and there is a need to come up with such innovative indigenous testing options.