UP uses rapid antigen tests to boost testing
Amid a surge in new Covid-19 cases in Uttar Pradesh, a data analysis by HT shows that the state government has relied on rapid antigen tests to improve testing numbers — an area in which India’s most populous state has been a laggard so far.
In the week ending on Saturday, an average 93,770 samples were tested in Uttar Pradesh every day — the highest in the country in absolute numbers. The next closest state in terms of daily tests was Tamil Nadu with 61,626 samples tested on average every day in the last week — 34% fewer than UP.
A month ago, for the week ending July 1, UP was testing 22,218 samples a day on average, while Tamil Nadu was testing 32,338 (45% more). In fact, two other states – Maharashtra (24,135 daily tests) and Andhra Pradesh (24,028) – tested more than UP as well. This shows how testing has been ramped up in UP over the past few weeks (Chart 1).
To be sure, this increase in testing was much needed in UP, in the backdrop of the state’s massive population of 225 million. A month ago, the state conducted 3,373 tests per million residents, the lowest in the country after Bihar (2,493 tests per million) and Telangana (1,913) against the then national average of 6,794 tests per million. Since then the state has climbed two spots and has tested 10,571 sampled per million; though it remains significantly lower than the national average of 14,871 (Chart 2). Much of the increase can be attributed to the state’s decision to start using antigen tests.
An antigen is a protein that induces an immune response in the form of production of antibodies against a disease, and detecting its presence through an antigen-based test determines a present infection. Since these tests can possibly lead to false negatives, several cases can slide under the radar. But experts say it can be used in small areas of hot spots to test every resident and quickly isolate as many patients as possible.
In contrast, the real-time reverse transcription-polymerase chain reaction (RT-PCR) test is the gold-standard for Covid-19 testing. It is used for the qualitative detection of nucleic acid from the Sars-CoV-2 in upper and lower respiratory specimens and is primarily based on PCR, a process that duplicates and amplifies genetic fragments of the virus, so that it becomes easily detectable. Experts say this is the most definitive test currently available and should be used as often as possible.
On July 20, when the state tested 40,659 samples, only 7,780 or 19.1% of tests were antigen tests (Chart 3). This share of antigen tests in the total samples tested in the state has been increasing daily since. As of August 1, nearly 69% of the 114,844 samples tested in the state were antigen-based.
In the same time period, while RT-PCR tests have largely remained the same (in the 30,000-a-day range), antigen tests have grown 10-fold (from 7,700 tests a day on July 10 to 78,000 tests a day on August 1). The strategy applied by the UP government is not unheard of. Nearly one in four Covid-19 tests conducted across the country currently uses a rapid antigen test kit, HT reported on Saturday. Delhi, which is perhaps the only region in the country that has managed to control the outbreak, has also relied heavily on antigen tests to scale its testing – on July 30, for instance, 71.6% of all tests performed in the capital were antigen-based.
A senior doctor with the core team of Kanpur’s chief medical officer (CMO), who did not wish to be identified, said the decision to rely on antigen tests so heavily was based on the limited number of RT-PCR labs and machines. The target for daily tests was not achievable without ramping up the scale of rapid antigen tests, the doctor said, adding that the number of machines available as of now was “clearly not enough”.
Experts say the lack of infrastructure related to RT-PCR tests remains a major challenge for the UP government, especially with he monsoon, which sees a massive spike in infections, underway. “Monsoon is favourable for the spread of infection. RT-PCR is the gold standard to test and identify cases early and accurately. Satellite testing centres should be made and RT-PCR machines should be placed for a population of every two lakh. In a city such as Lucknow, there should be at least 100 RT-PCR machines placed in different areas,” said professor TN Dhol, ex-head of the department of microbiology at the Postgraduate Institute of Medical Education and Research, Chandigarh.
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