Chief Minister Arvind Kejriwal responded Wednesday afternoon after the Delhi High Court pulled up his government for making Rapid Antigen Test (RAT) the primary test to detect the novel coronavirus despite its high rate of false negative results.
Defending his government's approach, Mr Kejriwal said he was following existing guidelines and that authorities had been directed to conduct a follow-up - using the RT-PCR method which is considered more accurate - on all those who displayed symptoms but returned a negative RAT result.
"Existing guidelines say that if any patient's antigen test is negative but has symptoms, RT-PCR test must be done on him. I directed the officers today to ensure strict compliance of these guidelines," he tweeted.
On Tuesday the court asked the Arvind Kejriwal government, which is capable of conducting 11,000 RT-PCR tests a day, why it had not conducted more than 600 tests per day between July 15 and July 23.
The court cited the results of the recent sero-survey that showed that most of the 23 per cent of COVID-19 patients in Delhi were asymptomatic and said RT-PCR tests were important in such situations.
The Delhi government said those diagnosed with SARI (severe acute respiratory illness) would have to undergo antigen tests first, prompting the court to ask the government to "strictly follow ICMR guidelines".
The ICMR (Indian Council for Medical Research, the government's nodal body in this health crisis) told the court that conducting antigen tests in such a situation was a deviation from its guidelines, which recommend RT-PCR for such individuals.
The RT-PCR gives a positive result only if the virus is present in the blood.
By contrast, the RAT can detect the virus only in people who contracted the disease at least a fortnight ago and consequently developed antibodies in their bloodstream.
So while the test can accurately detect how far the infection has spread in an area, it cannot detect live cases and help contain the spread.
The drop in RT-PCR testing has also coincided with a drop in the number of new cases reported in the national capital every day.
This has gone down from between 1,000 and 2,000 per day to below 1,000; on Monday the city recorded only 613 fresh infections - its lowest per day increase in two months.
Data analysed by NDTV showed that between June 18 and July 24, Delhi conducted 4,04,141 Rapid Antigen Tests. Among those tested, 2,818 symptomatic people who tested negative went through an RT-PCR test. Of them, 404 people tested positive, indicating that the false negatives rate of Rapid Antigen Tests is 14 per cent.
Delhi, the third worst hit region in the country, has nearly 1.33 lakh cases so far, of which fewer than 11,000 are active cases and 3,881 are deaths.
The recovery rate is around 88 per cent.
On Monday Mr Kejriwal praised the "hard work and mindfulness of two crore people in Delhi" for the "improving situation" in the national capital.