Home > News > India > Everything you wanted to know about India's test numbers, in five charts

Some of the most contested questions regarding the coronavirus pandemic revolve around testing. Has India been able to ramp-up testing? Is it enough? Are all states testing enough people? Are countries and states with low rates of testing paying a higher price in terms of higher covid-related fatalities.

A Mint analysis of testing data suggests that there is no strong link between testing rates and fatality rates across countries. However, the analysis suggests that countries that have been able to test more have also been able to ease lockdown restrictions more or earlier, suggesting that they are perhaps more aware and, hence, more confident about the spread of covid-19 in their countries. India may not have had to pay a high price for its low levels of testing in terms of fatalities, but the low levels of testing may have led to a much more stringent and prolonged lockdown than in most other parts of the world.

At first glance, the testing numbers suggest that India is not testing enough. Despite a ramp-up in testing, it still tests fewer people than many other affected countries.

When the nationwide lockdown was imposed on 25 March, India was conducting 539 tests per million people and ranked 52nd among countries in terms of the testing rates. Since then, test numbers have risen 47-fold even as case numbers have risen more than a hundred times, with India now conducting 758 tests per million, making it the 24th ranked country in terms of tests per million as of 3 May.

Yet, as officials from the Indian Council of Medical Research (ICMR) have pointed out, India also has found fewer positive cases for each test it has conducted (yield rate), and hasn’t had to pay a heavy price in terms of fatalities so far.

Evidence from around the world also seems to suggest that there is no simple linear relationship between testing and fatality rates. Some countries which tested aggressively early on (when cases were fewer) such as Italy and Belgium ended up having very high fatality rates.

Yet, given that this is an ongoing pandemic, and the virus case count is still rising, especially in Asian countries such as India, it is too early to say whether ICMR’s testing strategy has been proved right.

“These indicators cannot be considered in isolation as they are at best indicative, and depend on testing capacity, health care system, infection stage, and demographic factors of countries," said Tanmay Mahapatra, epidemiologist with CARE India, a not-for-profit working in the healthcare sector.

At the moment, India’s fatality rate (less than 4 percent) appears relatively low compared to countries with large outbreaks such as Italy and the UK but India’s death count is rising fast, and we still don’t know when it will peak, or if there will be more waves of infections after the first peak. Nonetheless, compared to countries such as Indonesia and Mexico, which have low testing rates, high yield (positive cases per test) rates and higher fatalities, India appears to be better placed so far.

Within India, the states with the highest testing rates - Andhra Pradesh, Delhi, Tamil Nadu, and Rajasthan have so far had lower fatality rates. States that have reported high case fatality — Maharashtra, Gujarat, Madhya Pradesh, West Bengal and Karnataka have either low or moderate testing rates. Of these, West Bengal and Madhya Pradesh have high positivity levels as well. This suggests they may not be testing enough despite indications of higher prevalence.

To be sure, there are limitations in this comparison. Positivity or yield rate is a function of the testing strategy and of how well it captures the segment of the population that is most likely to be at risk. Also, fatality counts depend not just on the extent of early detection (which adequate testing can ensure) but also on other factors such as access to medical care, age of patients, comorbidities and even the way causes of death are being reported across regions.

Nonetheless, the data suggests that early detection through greater testing may help. For instance, Delhi ramped up testing early on and saw faster growth (49.5%) in cases up to the 500th case. However, the growth of cases slowed down later on. At the other extreme, Punjab which was slow in ramping up testing early on saw a much larger spike in cases in the later stages, and continues to witness a surge in cases. This analysis is based on states that had more than 500 cases as of May 3.

“We made a big mistake in the early stages of not testing enough," said Jacob John, professor of epidemiology and community medicine at the Christian Medical College (CMC) Vellore. “There is no doubt that we are in the community transmission stage."

ICMR officials have so far denied community transmission but given the limited testing so far, and the lack of any random sampling in the population, the true extent of covid-19 prevalence in the country remains unknown. It is this uncertainty, and the fact that the corona case curve is not bending, that have led to a prolonged lockdown which has not only wrecked livelihoods of millions but also jeopardized routine (non-covid) health services.

Countries which adopted extensive testing in early stages of the pandemic had much less stringent restrictions compared to India, and have already been able to lift most of such restrictions.

Can India get a better handle on the spread of the epidemic in the coming days? The answer to that may well determine how fast and how sustainable the opening up of the country is going to be.

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