For Faster Diagnosis, ICMR Recommends Antigen-Based Testing Kit for Covid-19

The use of Standard Q COVID-19 Ag detection assay (antigen detection test) as a point of care diagnostic assay has been advised by the Indian Council of Medical Research (ICMR) for testing in combination with RT-PCR test under certain settings.

On Sunday, ICMR in an advisory stated that those 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 require any reconfirmation by RT-PCR test.

As India looks to increase testing to deal with the surge in coronavirus infections, a Korean company’s antigen test kit produced by the firm SD Biosensor gives results in 30 minutes has been validated by the Indian Council of Medical Research (ICMR) and All India Institute of Medical Sciences (AIIMS). The kit which has a manufacturing unit in Manesar, Gurugram, can be used in field settings. If the result of the antigen test comes out as positive, it can be considered as a confirmation of the infection. If it shows a negative result, then ICMR has recommended that an RT-PCR test also be done to rule out the possibility of an infection.

Dr. LK Sharma, Scientist and Media Coordinator at ICMR told that a positive test in antigen should be considered as a true positive and does not need reconfirmation by RT-PCR test. It will show whether the patient is currently infected or not. When enquired about the price of the kit, Dr. Sharma explained that the company will be able to provide details on the pricing of the kit and added that it is up to state governments to decide how they want to procure the kits.

HOW DOES IT WORK?

The kit has several components as it comes with an inbuilt COVID antigen test device, viral extraction tube with viral lysis buffer, and sterile swab for sample collection. The antigen test needs a nasal swab while antibody tests require drawing of blood. This nasal swab is collected using the customized sample collection swab provided along with the kit. No other swab, throat or bronchoalveolar lavage or sputum, is required.

Viral extraction buffer which is provided in the kit is used to collect swab and is then immersed and squeezed in which the virus is inactivated if present in the swab sample. It is transferred from the buffer tube to a nozzle provided with the kit and 2-3 drops of the sample are put into the well of the test strip, and it resembles a home pregnancy kit strip.

The appearance of the test and control lines on the strip would confirm in 15 minutes whether the test is positive or negative. According to ICMR, the kit’s accuracy or specificity in detecting true negatives is between 99.3 % to 100 % based on validation done at two sites. The kit’s rate of detecting infections correctly or sensitivity ranged from 50.6% to 84% based on two independent evaluations. It also depends on the viral load of the patient, the ICMR mentioned, as higher viral load correlated with higher sensitivity.

WHERE CAN THESE KITS BE USED?

The ICMR specified that in view of the high specificity and relatively low sensitivity, ICMR advises the use of the test kit in containment zones or hotspots to test symptomatic persons with influenza-like illness and asymptomatic direct and high-risk contacts with co-morbidities of a confirmed case. They should be tested once between day five and day ten of coming into contact with such individuals.

ICMR also stated that it is helpful in healthcare settings, this testing kit can be used to test for all symptomatic patients undergoing chemotherapy, patients with influenza-like illness, patients with malignant disease, and elderly patients.

Over to you

There are no such reliable antigen detection tests available worldwide, which could be used as a rapid point of care tests for quick detection of COVID-19 positive patients. Such rapid antigen tests would help in the proper implementation of the Government strategies to test, track, and treat. Such tests will also assist in allaying the anxiety and fear of healthcare workers and aid in the better clinical management of the patients and the government can arrange for more resources as per the situation.