Rapid antigen test COVID procedure The simple and fast method

Rapid antigen test COVID procedure The simple and fast method of dry swab-direct RT-PCR, developed by CSIR’s constituent lab Centre for Cellular and Molecular Biology (CCMB), Hyderabad, for scaling up coronavirus detection has now been approved by the Indian Council of Medical Research, the apex body announced on Friday.

Rapid antigen test COVID procedure


This method developed by CSIR-CCMB is a simple variation of the existing gold standard RT-PCR method and can easily scale up the testing by two to three fold with no new investment of resources.

After evaluating this method and finding an overall concordance of 96.9 per cent, the ICMR has now issued an advisory for the use of CSIR-CCMB dry swab method, considering its lesser cost and quick turn-around time.

CSIR-CCMB has been testing samples for coronavirus since April 2020. Having worked closely with the healthcare workers of Telangana, it identified some of the key issues that slow the testing process. In response to it, the researchers here developed the dry swab RNA-extraction free testing method for Covid-19.

More specifically, the dry swab-direct RT-PCR method involves collecting and transporting the nasal swab in dry state (as opposed to using the viral transport medium VTM) which makes the transportation and handling of the samples easy and less prone to spillage and spread of infection.

Secondly, the step of RNA isolation from the sample is omitted and involves only simple processing of the sample followed by direct RT-PCR using the kit recommended by ICMR.

Omitting the step of RNA isolation offers a huge benefit over the conventional method, as the RNA isolation is a major bottleneck in terms of time, cost and trained manpower.

Commenting on the development, the Director General of CSIR, Shekhar C. Mande, said that the method is easy to implement with no requirement of new kits and the existing manpower can perform this with no additional training and hence could make a significant contribution to ramping up the testing capacity in the country quickly.

Rakesh Mishra, Director, CCMB, said, “RNA extraction, even with automation, takes four hours for roughly 500 samples. VTM and RNA extraction both add a significant burden on money and time required for mass testing for coronavirus. We believe the technique’s merit holds for all kinds of settings and has the potential of bringing the costs and time of testing by 40-50 per cent.”

Significantly, the modified method of CSIR-CCMB has also been independently corroborated by multiple premier institutes and hospitals such as the Centre for DNA Fingerprinting and Diagnostics (CDFD), IISER-Berhapmur, CSIR-Neeri, GMCH-Nagpur, Genepath based in Pune, IGGMSH and MAFSU, Nagpur and also Apollo Hospitals, Hyderabad.

This modified method has been published in peer reviewed journal by CSIR-CCMB and across the globe by other scientific groups in several prestigious scientific journals across the world


Principle of the Test

COVID-19 Antigen Rapid Test is a rapid membrane-based lateral flow immunoassay for the qualitative detection of SARS-CoV-2 antigens in human nasopharyngeal and nasal swab specimens. During the test, any SARS-CoV-2 antigens contained in the sample react with the antibody-coated nanoparticles contained in the reactive test strip. As a result, the blend migrates chromatographically by capillary action along the reactive strip.
If the specimen contains SARS-CoV-2 antigens, these will bind to SARS-CoV-2 antibodies contained in the (T) Test line region and generate a colored line on the test strip, indicating a positive result. If the antigens are not present in the specimen, no colored line will appear in the (T) Test line region, indicating a negative result. As a procedural control, a colored line will always appear in the (C) Control line region, indicating the test procedure has been performed properly and that test components have worked as intended.

COVID-19 Antigen Rapid Test is addressed to healthcare professionals with the aim to support them in COVID-19 emergency management, by receiving prompt results on the health status of their patients:
– high Sensitivity and Specificity standards, when compared to a PCR Methodology;
– safe and accurate results in only 15 minutes;
– easy to use and to read.

Why using a COVID-19 antigen test?

The use of a COVID-19 Antigen Rapid Test allows to detect the presence of SARS-CoV-2 antigens in our body and to take initial precautionary isolation measures in order to reduce the spread of the virus.
As stated by Mina et al. in the New England Journal of Medicine, due to the constant high incidence of COVID-19 cases worldwide, there is a high need for accurate and reliable diagnostic devices that are easy to use and have a prompt response, in order to enable frequent testing operations. Constant high incidence of COVID-19 cases worldwide, there is a high need for accurate and reliable diagnostic devices that are easy to use and have a rapid response, have been developed, in order to facilitate the diagnosis and traceability of newly infected people: the antigen tests.
Since the transmission of the SARS-CoV-2 virus seems to occur days after exposure, when the viral load reaches its peak, the frequency of testing is increasingly important in order to slow down the spread of the pandemic, as shown in Figure 1.

Figure 1

The criteria expressed in Figure 1 could be defined as a surveillance method, intended to reduce the number of people affected by SARS-CoV-2 and give rapid results, in order to minimize the asymptomatic spread. This surveillance approach cannot be performed using the standard PCR technique because, after collection, PCR samples usually require transport to specialised laboratories run by experts, this in turn requires one or more days for the results, creates a bottleneck and is expensive.

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