As India looks to ramp up testing to deal with the surge in coronavirus infections, a Korean company’s antigen test kit that 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 produced by the firm SD Biosensor, 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 infection.
“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,” said Dr LK Sharma, Scientist and Media Coordinator, ICMR.
When asked about the price of the kit, Dr Sharma said 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 comes with an inbuilt Covid antigen test device, viral extraction tube with viral lysis buffer and sterile swab for sample collection. Unlike antibody tests which require drawing of blood, the antigen test needs a nasal swab. This swab is collected using the customised sample collection swab provided along with the kit. No other swab, throat or bronchoalveolar lavage or sputum, is needed.
The collected swab is immersed and squeezed in the viral extraction buffer which inactivates the virus, if present in the swab sample. From the buffer tube, it is transferred to a nozzle provided with the kit and 2-3 drops of the sample are put into the well of the test strip, which looks similar to a home pregnancy kit strip.
In 15 minutes, the appearance of the test and control lines on the strip would confirm whether the test is positive or negative. According to ICMR, the specificity or the kit’s accuracy in detecting true negatives is between 99.3% to 100% based on validation done at two sites. The kit’s sensitivity or the rate of detecting infections correctly ranged from 50.6% to 84% based on two independent evaluations. It also depends on the viral load of the patient, the ICMR said, as higher viral load correlated with higher sensitivity.
Where can states use these kits?
The ICMR said that in view of the high specificity and relatively low sensitivity, ICMR recommends 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 said that in healthcare settings, all symptomatic patients with influenza-like illness, patients undergoing chemotherapy, patients with malignant disease and elderly patients can be tested using this kit.