The Indian Council of Medical Research (ICMR) has recommended the use of Standard Q COVID-19 Ag antigen detection test in containment zones and healthcare settings in combination with the RT-PCR test. Collected nasal swab is used for testing in this procedure.
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“A positive test in antigen, result of which is available in 30 minutes, should be considered as a true positive one and does not need reconfirmation by RT-PCR test. It will show whether the patient is currently infected,” said L.K. Sharma, scientist and media coordinator, ICMR, on Monday.
The kit, validated by the ICMR and the All India Institute of Medical Sciences (AIIMS), was different from the Rapid Antibody Test kit. “Sample is nasopharyngeal swabs in this test, while blood is collected in the antibody test. The kits will allow faster diagnosis,’’ he stated.
The Standard Q COVID-19 Ag detection kit is a rapid chromatographic immunoassay for qualitative detection of specific antigens to SARS-CoV-2. It has been developed by SD Biosensor, a South Korea based company, having its manufacturing unit in Manesar, Gurugram.
High specificity
An advisory released by the ICMR stated that in view of the high specificity (ability to detect true negatives) and relatively low sensitivity, the Council recommends the use of this test 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,’’ the ICMR said. In healthcare settings, all symptomatic patients with influenza-like illness, patients undergoing chemotherapy, patients with malignant disease and elderly patients could be tested using this kit, it noted.
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“The test can be interpreted as positive or negative after 15 minutes of putting the sample into the well by appearance of test and control lines, which can be read with a naked eye, requiring no specialized equipment. The maximum duration for interpreting a positive or negative test is 30 minutes. After that, the test strip should be discarded. The test kit should be stored between 2° to 30° C,’’ the ICMR said.
“Specificity ranged from 99.3 to 100% at the two sites and sensitivity of the test [i.e. ability to detect true positives] ranged from 50.6% to 84% in two independent evaluations, depending upon the viral load of the patient. Higher viral load correlated with higher sensitivity,’’ it added.
Published - June 15, 2020 08:13 pm IST
