New Delhi: Indian Council of Medical Research (ICMR) has recommended the use of Standard Q COVID-19 Ag detection assay (antigen detection test) as a point of care diagnostic assay for testing under certain settings in combination with RT-PCR test. 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 need reconfirmation by RT-PCR test, said ICMR in an advisory on Sunday.


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One of the brief descriptions of the Standard Q COVID-19 Ag detection is that 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. 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.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 in the following settings in combination with the gold standard RT-PCR test--A. Containment zones or hotspots (to be performed onsite under strict medical supervision and maintaining kit temperature between 2° to 30° C.):i) All symptomatic Influenza Like Illness (ILI). ii) Asymptomatic direct and high-risk contacts with co-morbidities (lung disease, heart disease, liver disease, kidney disease, diabetes, neurological disorders, blood disorders) of a confirmed case to be tested once between day 5 and day 10 of coming into contact.


B. Healthcare settings (to be performed onsite under strict medical supervision and maintaining kit temperature between 2° to 30°


C): i) All symptomatic ILI patients presenting in a healthcare setting and are suspected of having COVID-19 infection. ii) Asymptomatic patients who are hospitalized or seeking hospitalization, in the following highrisk groups: Patients undergoing chemotherapy, Immunosuppressed patients including those who are HIV+; Patients diagnosed with malignant disease; Transplant patients; Elderly patients (>65 yrs of age) with co-morbidities (lung disease, heart disease, liver disease, kidney disease, diabetes, neurological disorders, blood disorders) iii) Asymptomatic patients undergoing aerosol-generating surgical / non-surgical interventions: Elective/emergency surgical procedures like neurosurgery, ENT surgery, dental procedures; Non-surgical interventions like bronchoscopy, upper GI endoscopy and dialysis;ILI case is defined as one with acute respiratory infection with fever >= 38*C and cough.


Use of the rapid antigen test is recommended in A & B categories above subject to the following conditions:


i) 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.


ii) Samples (only nasopharyngeal swabs) to be collected by a trained healthcare worker following full infection control practices including use of proper PPE.


iii) The test should be conducted onsite under strict medical supervision and within one hour of sample collection in extraction buffer.Giving a background, the ICMR said, "Real time RT-PCR is the gold standard frontline test for diagnosis of COVID19. Various open and closed RT-PCR platforms (Open systems RT-PCR machines, TrueNat and CBNAAT) are currently being used for COVID19 diagnosis in India.''


All these platforms require specialized laboratory facilities in terms of equipment, biosafety and biosecurity. Minimum time taken for the test varies between different systems with a minimum of 2-5 hours including the time taken for sample transportation. 


These specifications limit the widespread use of the RT-PCR test and also impedes quick augmentation of testing capacity in various containment zones and hospital settings.


"In view of this, there is urgent need of a reliable point-of-care rapid antigen detection test with good sensitivity and specificity for early detection of the disease," it said.


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


In view of this, an independent two site evaluation of the only available or standalone antigen detection assay: Standard Q COVID-19 Ag detection kit, was conducted with an aim to evaluate its sensitivity, specificity and feasibility of use as a point-of-care test for early detection of SARS-CoV-2.