Written by Karishma Mehrotra | New Delhi | Published: June 16, 2020 2:10:15 am
Laboratories usually take a day to give results in case of an RT-PCR test. (File photo)
As the country ramps up its Covid-19 testing, the Indian Council of Medical Research (ICMR) has approved a new on-site diagnostic kit for containment zones and healthcare settings, which can produce rapid results without needing a laboratory and cost much less.
Unlike the RT-PCR test used for diagnosis now — requiring heavy laboratory work to multiply the genetic material of the virus — the rapid antigen detection test is reliant on the amount of virus, or the virus load, in a nasal swab. It can give a result in 30 minutes. An antigen means any toxin in the body which produces an immune response.
Laboratories usually take a day to give results in case of an RT-PCR test.
On Monday, the coronavirus case count in India stood at 3,32,424. A total of 57,74,133 samples have been tested, of them more than 1,15,000 in the past 24 hours.
In containment zones, the rapid antigen test would be used for all people with high fever and cough (influenza-like illnesses) and all contacts of a case who are direct, asymptomatic, and have high co-morbidities.
In healthcare settings, the test will be used for all patients of influenza-like illnesses (ILIs) who are suspected of having Covid-19 and asymptomatic patients who are immunosuppressed, have had transplants, or are undergoing chemotherapy, have a malignant disease, or other co-morbidities. The test will also be available for asymptomatic patients undergoing certain procedures or interventions such as neurosurgeries, dental work, dialysis and bronchoscopies,
However, the rapid test has been found to have a higher chance of false negatives. So, while positive results will be considered confirmed, in case of negative results, an RT-PCR would be done for reconfirmation.
On May 9, the US’s Food and Drug Administration had given emergency authorisation for use of such an antigen test kit. Japan approved a similar test kit four days later. Some experts worldwide have considered deploying these tests as home-kits in the future.
As per the Indian Journal of Medical Research (IJMR), out of all people eligible for testing under the ICMR criteria, asymptomatic direct and high-risk contacts of a case made up the largest chunk of both confirmations (25%) and tests (20%) between January 22 and April 30.
While the above category was added for testing by the ICMR only on March 20, it had expanded the categories on May 18 to include hospitalised ILI patients, indicating a concern over contracting coronavirus in hospitals.
Another low-cost test kit, TrueNat, originally developed for tuberculosis, is being deployed at less-equipped district hospitals. Officials said 77 TrueNAT machines are in use currently.
The ICMR advisory on Monday stated: “There are no reliable antigen detection tests available worldwide, which could be used as rapid point of care tests for quick detection of Covid-19 positive patients. Such tests will also help in allaying the anxiety and fear of healthcare workers and aid in better clinical management of the patients.”
The advisory said that the ICMR and AIIMS had evaluated the “only available or standalone antigen detection assay”, developed by South Korean company SD Biosensor, before selecting it. “ICMR encourages other manufacturers /developers who have antigen detection assays to come forward for validation,” the note said.
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