Covid-19 testing rates do not match mortality rates

Updated: May 05, 2020 3:26 PM

We should continue to implement all the needed public health measures instead of projecting testing rates as the sole path to salvation

Reduced mortality is the ultimate objective of our response to the Covid-19 epidemic.Reduced mortality is the ultimate objective of our response to the Covid-19 epidemic.

By K Srinath Reddy & Surabhi Pandey

High levels of testing for the Covid-19 virus have been advocated for control of the pandemic, and testing rates are frequently cited to judge the quality and effectiveness of a country’s health system response. India’s testing rate has frequently come under criticism by both domestic and international commentators. By implication, it is suggested that a low testing rate will result in a poorly controlled epidemic and, therefore, a high mortality rate. How extensive should the testing be at different stages of the epidemic, and for what indications, has been debated. This has been further confounded by the observation that a large number of infected persons may remain asymptomatic and difficult to detect even by extensive testing. A further concern relates to the variable rates of false negatives and false positives that even RT-PCR tests are revealing.

In this context, we regard the most important question to be whether high testing rates are associated with lower death rates. Reduced mortality is the ultimate objective of our response to the Covid-19 epidemic. To answer this, we examined the relationship of tests per million and deaths per million in a number of countries grouped into geographic zones (see graphics). There was no relationship between testing rates and mortality rates in any region. Even on taking all countries together, there is no correlation to suggest that high testing rates are associated with lower mortality.

Testing is only one of the components of the public health response needed to counter Covid-19. Syndromic surveillance, contact tracing, physical distancing, masks and hand hygiene are important elements, too. Indeed, given the challenges of identifying asymptomatic infected persons and false test results, the last three measures will remain the most effective shield against virus dissemination as we release ourselves from the lockdown. To project testing as the acid test of a health system’s response is misleading, if our goal is to reduce deaths.

The situation may change if Covid-19 specific drugs are developed with demonstrated impact on reducing mortality. Even then, the treatments will have been tested in symptomatic cases. The current testing protocols in India cover that. To do a general screening for employees returning to work has illusory appeal, but there is no assurance that a negative antigen test is a certificate that remains valid even a day later in a post-lockdown open society. Will any lab certify that an employee who tests negative today will not get infected four days later and will not infect colleagues a week later? The WHO has stated that antibody tests, too, cannot be regarded as ‘immunity passports’, can yield false results, and are useful only for surveillance and research. We should continue to implement all the needed public health measures instead of projecting testing rates as the sole path to salvation.

Authors are with the Public Health Foundation of India. Views are personal

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