The number of new COVID-19 cases in India recorded a significant fall in the last five days after consistently breaching the 90,000 mark on several days in early September. The drop in cases could be due to a significant decrease in the number of tests conducted.
In at least 10 States, there was a sharp fall in the number of tests conducted in the last 10 days despite an increase in the share of people testing positive.
Rapid fall in tests
Over the last 10 days, the number of new COVID-19 tests conducted per million people in India has been declining rapidly. While the share of people testing positive (positivity rate) has remained high and even increased a little over the last five days, the number of tests per million people dropped from 811 to 722 over the last 10 days. The share of positive tests is hovering around the 8.5% mark.
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Among States
Not all States recorded a decline in tests. They can be classified into three types based on their recent testing levels.
The bad : In Maharashtra and Assam, tests are going down, while the share of positive cases is going up. Using such a strategy would mean missing a lot of positive cases.
Other States in this category include Arunachal Pradesh, Goa, M.P., Nagaland, Sikkim, Tripura, Chhattisgarh and Karnataka.
The good : In T.N., tests are going up, while the positivity rate is going down. Other States include Delhi, Bihar, Jharkhand, Mizoram and W.B.
This is the ideal strategy. Despite the positivity rate going down, tests need to be scaled up or maintained at a certain level. Such an approach is required as sero-surveys show that for every confirmed case, there were 82-130 undetected infections in India.
Thus, the more the tests, the better, regardless of the positivity rate
Middling States : In Gujarat and Telangana, tests are dropping, but the share of positives is also going down. In these States, tests should be maintained at a certain level, if not increased, to ensure that the share of positives does not necessarily go down due to decreasing testing levels.
In Andhra Pradesh, tests as well as the share of positives are rising. Such States need to increase their testing levels to capture more positives. Nine other States are following this trend: Haryana, J&K, Punjab, Rajasthan, Uttarakhand, Manipur, Meghalaya, U.P. and Kerala.
Last word
The positivity rate varies widely based on the method of testing. For instance, over the past seven days, 81% of tests in Delhi were Rapid Antigen Detection Tests (RADT), which are not as reliable as RT-PCR tests . RADTs can register as many as 50% 'false negatives'.
In Tamil Nadu, RADTs are not used. Thus, while the positivity rate in T.N. may be closest to the actual rate, the same cannot be said about Delhi. The share of RADTs in select States is as follows: A.P. (54%), Chhattisgarh (68%), Karnataka (42%), W.B. (55%), Mizoram (25%), Nagaland (7%).
