Abbott antigen kit gets US nod, no India plan
The US multinational Abbott on Thursday announced that the US Food and Drug Administration (FDA) has approved its rapid antigen kit to test for coronavirus disease (Covid-19). However, the company does not have any immediate plans to launch the kit in India.
“As of now the test is launched only in the US,” said a company representative to HT.
The kit gives results in 15 minutes, with a sensitivity (ability to detect true positives) of 97.1% and specificity (ability to detect true negatives) of 98.5% in clinical studies, making it a more accurate antigen-based test available in the market. The test costs $5.
In June, Abbott had launched its laboratory-based serology blood test for the detection of the antibody, IgG (Immunoglobulin G), that identifies if a person has had past exposure to SARS-Cov-2, the virus that causes coronavirus disease (Covid-19), in India. The kits are being in used government and private hospitals and labs in Maharashtra, Delhi, West Bengal, Uttar Pradesh, Jammu & Kashmir and Gujarat, the company had said in a statement.
ICMR has approved Abbott’s CLIA (Chemiluminescence immunoassay) antibody tests that are technologically advanced.
Experts using these kits say this technology is more accurate than the rapid antibody test kits. “CLIA is a technologically more advanced platform, which is why the result is also more accurate. These kits are giving satisfactory results,” said a lab in-charge for Covid-19 testing in Delhi, requesting anonymity.
Due to its moderate sensitivity, experts in India have been critical of antigen-based testing. The data made public by the Indian Council of Medical Research (ICMR) on the first kit independently evaluated by its lab in National Institute of Virology in Pune, and the All India Institute of Medical Sciences in Delhi, found sensitivity ranging from 50.6% to 84%, and specificity of 99.3 to 100% at the two sites. Currently, between 30-40% of Covid-19 tests in India are performed using rapid antigen kits.
“The low sensitivity of the test is the reason why it is suited more as a screening test rather than a confirmatory test. However, since positives are confirmed positives it can be deployed where mass testing is required, especially in containment zones, and the negatives can be re-tested using RT-PCR, which is the gold standard. However, if the sensitivity of the test is increased then chances are higher of the result being more accurate and can work well with an RT-PCR test,” says Dr T Jacob John, former head, virology department, Christian Medical College, Vellore.
The reverse transcription polymerase chain reaction (RT-PCR) test is the gold standard for covid-19 diagnosis, but antigen-based testing is currently being used to supplement the testing process for diagnosis as it also helps determine the current infection in a shorter duration, without the need for a sophisticated laboratory and at a lower price as compared to RT-PCR.