The diagnostic test

The gold-standard test for Covid-19 is qRT-PCR. This stands for quantitative, reverse transcriptase polymerase chain reaction. In essence this converts viral RNA to DNA and then amplifies the DNA for detection.

There is much written about the shortage of “kits”. These are now available

https://www.biovision.com/coronavirus-sars-cov-2-pcr-detection-kit.html

Unique to a kit is the specific primers to identify the viral gene and the positive control for the disease.

The test subject must first be swabbed and the hope is that if the subject is affected by the disease:

  • He or she will be shedding virus onto the membrane that is swabbed
  • That the swab will pick up the virus
  • That the virus will survive the transport to the lab

Then the RNA needs to be extracted from the swab using a protocol similar to

The cotton tips were stored in 350 µL phosphate buffered gelatin saline (PBGS). For the extraction, the cotton tip was lifted out of the PBGS and placed in a clean microcentrifuge tube. The extraction was conducted using the RNeasy Plus Mini Kit (QIAGEN) following the manufacturer’s instruction for tissue samples.

Habarugira, Gervais, et al. “Mosquito-Independent Transmission of West Nile virus in Farmed Saltwater Crocodiles (Crocodylus porosus).” Viruses 12.2 (2020): 198.

The extracted RNA needs to be processed in a qRT-PCR machine using the kit. Machines are available as 96 or 384 well devices – this is the number of simultaneous tests that can be done.

The test run takes 2-3 hours to do.

There has been some promising development of a new test for the virus known as RT-LAMP https://www.medrxiv.org/content/10.1101/2020.02.19.20025155v1

The new test uses a different enzyme for dna polymerization and does not require thermal cycling. Theoretically, the test could be read by naked eye in the field

Although this is yet to be validated on real virus or virus samples, it is a very positive development. The test could theoretically be done in the matter of hours at the doctor’s surgery