Decline in Covid infection welcome, but test quality must improve: Analysis

Govt must focus on testing vulnerable groups in the shortest span of time, experts say
A health worker collects a sample from a child in Bengaluru. (Photo | Meghana Sastry, EPS)
A health worker collects a sample from a child in Bengaluru. (Photo | Meghana Sastry, EPS)

BENGALURU: The number of daily additions to Bengaluru's Covid cases may be on the decline, but there is room for increasing qualitative testing to detect more positive cases and avoid a potential increase in severe infections or mortality, according to an analysis by a management consultancy.

Bengaluru's Effective Testing Positivity Rate (ETPR) was 17.5% in early September and dropped to 13% on November 8, showed the analysis by Jeevan Raksha, an initiative of consultancy Proxima. 

The ETPR is different from the Total Positivity Rate (TPR), which is the number of positives expressed as a percentage of the total number of tests.

The ETPR is the total number of new tests done on a daily basis, but excludes the positives from at least 20% of retests.

While the decline of the TPR is a welcome sign, the ETPR aims at increasing the 'positive' detection rate in the number of tests done per day.

This means that a reduction in the ETPR is not a good sign because it implies that tests are being done on healthier people instead of those who are likely to contract the infection-elderly people, those with comorbidities, pregnant women, those with weakened immunity, or those more exposed to the disease. 

An expert said that an individual whose first test came back negative but the second confirmed Covid-19 infection would be excluded from the ETPR.

These comprise at least 20% of people excluded from the ETPR, meaning that the decline in the ETPR is artificial as the precise number is ignored. 

In September, Bengaluru conducted a total of 6.6 lakh tests, resulting in 1.3 lakh positive cases.

In October, the number of tests rose to 10 lakh, but the number of positive cases remained at 1.3 lakh. Experts said this indicated lack of testing among high-risk categories.

Bengaluru recognised that testing was inadequate in August, and ramped up capacity, said Sanjeev Mysore, convenor of Jeevan Raksha.

"The active cases dropped sharply, month-on-month, and the number of deaths marginally reduced. Now, Bengaluru has got the quantitative aspect right, but it should give due attention to qualitative aspects which include tracing and testing the most vulnerable group within the shortest time span," he said.

The decline in the ETPR contradicts the results of both the government and private serosurveys, which found that up to 27% and 45% respectively of Karnataka's population had the infection at the time of survey or had been infected in the past. 

Poor testing yield indicates high probability of testing low-risk people without clear justification. Poor testing is also caused by high usage of Rapid Antigen Tests which have a high probability of false negative results. 

"Qualitative improvement in coming weeks could yield better results. If the right people are not traced and tested, the testing yield (those testing positive) will be less and low number of cases will be reported, but the threat of infection spread remains," Mysore said.

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