Dry swab test method cheap and best: CCMB study

The CCMB’s technique eliminates need for expensive cold chain network

Hyderabad: Maintaining a cold chain while transferring samples to a laboratory for RT-PCR testing to detect coronavirus significantly adds to the costs, time and even accuracy.

In a recent study by Hyderabad-based Centre for Cellular and Molecular Biology (CCMB), available online from May 31 in medRxiv, the preprint journal for health sciences, researchers have demonstrated that their dry swab technique does not need the expensive cold chain management and can be stored and transported at room temperature for up to 24 hours.

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The study indicated that dry swabs can be stored and transported for up to 24 hours around 25 degrees Celsius, which is almost room temperature. This means that instead of storing in an expensive Viral Transport Medium (VTM), which is then kept in a cold chain till the samples are delivered to a lab, the dry swabs technique of CCMB enables storage and transportation of samples sans a cold chain for at least 24 hours.

The dry swab-based direct RT-PCR testing, approved by ICMR, is a simple, inexpensive and safe method for coronavirus diagnosis. In this method, sample collection centres can send dry swab samples directly to testing centres without the need to have liquid VTM, the researchers said.

The collected samples are also stable for up to three days at four degrees Celsius, and the test result is comparable to the traditional VTM.

“Testing of the maximum population in less time and minimum cost with existing diagnostic amenities is the only possible way to control the Covid spread. The RNA extraction methods using dry swab is advantageous in these critical times,” the researchers said.

In the study, the geneticists showed stability and performance of the dry swab viral detection method at two different temperatures i.e. 25 degrees Celsius (room temperature) and 4 degrees Celsius and were later compared with the existing VTM-based method.

“The results clearly indicate that the dry swab technique of RNA detection is as efficient as the VTM-RNA-based method in both strains when checked for up to 72 hours (three days),” they said.

The lesser CT values of dry swab samples compared to that of the VTM-RNA samples suggest better sensitivity of the method within 48 hours. The results collectively suggest that dry swab samples are stable at room temperature for 24 hours and the detection of SARS-CoV-2 RNA by RT-PCR do not show variance from VTM-RNA, the CCMB study said.

This extraction-free, direct RT-PCR method holds phenomenal standing in the present life-threatening circumstances due to SARS-CoV-2, they added.

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