NEW DELHI: The government’s apex research body, Indian Council of Medical Research (ICMR), has recommended use of the first antigen-based testing kit for Covid-19 to enable faster diagnosis at lower rates and without laboratory examinations of samples.
The antigen test — developed by private biotechnology firm SD Biosensor — has also been validated by AIIMS, New Delhi, apart from ICMR and can detect presence of SARS CoV 2 in swab collected from the nose alone.
The test can detect presence of molecules of the pathogen that triggers immune response in Covid-19 infected persons. Maximum duration for interpreting a positive or negative test is 30 minutes through the antigen based kit.
“In view of its high specificity while relatively low sensitivity, ICMR recommends the use of Standard Q Covid-19 Ag detection assay as a point of care diagnostic assay for testing…,” ICMR said in an advisory recommending the antigen test in combination with the gold standard RT-PCR test.
While no confirmatory tests are required for samples testing positive, ICMR said those who test negative should undergo a RT-PCR test to rule out infection.
Last month, the US Food and Drug Administration also approved an antigen-based test, noting it is a new type of diagnostic test. “Each category of diagnostic test has its own unique role in the fight against this virus. PCR tests can be incredibly accurate, but running the tests and analysing the results can take time. One of the main advantages of an antigen test is the speed of the test, which can provide results in minutes.”
But antigen tests may not detect all active infections and are not as sensitive as molecular PCR tests. Hence, positive results are highly accurate, but there is a higher chance of false negatives. So negative results do not rule out infection, the FDA said. Similarly, ICMR has said negative results need to be confirmed with a PCR test prior to making treatment decisions or to prevent the possible spread of the virus.
“Suspected individuals who test negative for COVID-19 by rapid antigen test should be definitely tested sequentially by RT-PCR to rule out infection, whereas a positive test should be considered as a true positive and does not need reconfirmation by RT-PCR test,” said the advisory.
The agency has also said the testing kits be used for all symptomatic people with influenza-like illness (ILI) in containment zones or hotspots and asymptomatic direct and high-risk contacts with co-morbidities of confirmed cases.
In hospitals, the kits are to be used for all symptomatic ILI patients, asymptomatic patients who are hospitalised or seeking hospitalisation for chemotherapy and transplants or those who are over 65 years with co-morbidities.
In view of rising demand for testing, ICMR has also asked other manufacturers, who have antigen detection assays, to come forward for validation.
The move assumes significance as use of antigen kits is likely to boost testing because of its turnaround time as well as pricing. Officials said the antigen test is going to much cheaper as compared to RT-PCR kits.
At present, around 1.5 lakh RT-PCR tests are being conducted in the country everyday.