Background to Virolens
The Virolens system employs a holographic microscope combined with artificial intelligence (AI) to determine whether the SARS- CoV- 2 virus is present in a sample. Virolens does not use chemical or biological testing, but rather identifies the unique diffraction patterns created by light interacting with virus surface proteins to identify COVID- 19.
The technology has been developed by British company, i- Abra and is distributed by KeyOptions.
PCR vs Virolens - The difference between RNA presence and infectivity
The polymerase chain reaction (PCR) was a step-change in biology when it was invented in 1985. It is now the most used molecular biology technique in the world. PCR has enabled breakthroughs in medical research, forensics, and diagnostics.
PCR works by using even tiny amounts of genetic material (RNA or DNA) as a template and creating millions of copies of a small part of that genetic material. The process requires biological enzymes, as well as other inputs such as nucleotides, and “primers” (small segments of DNA that bind to the template). The samples go through a series of cycles of heating and cooling to allow the newly formed genetic material to become templates itself.
When used in viral diagnostics, this means that even a small number of genomes in a sample can provide a definitive positive result.
However, there is an important difference between viral RNA (in the case of SARS- CoV- 2) and infectious virus particles. The presence of a segment of viral RNA that can be amplified by PCR does not correlate well with the presence of infectious virus, and hence with infectivity.
For example, a 2021 meta- analysis of 79 studies involving 5,340 people showed that viral RNA was detectable by PCR for an average of 17 days (95% CI: 15.5–18.6) in the upper respiratory tract, however no study reported viable virus production after 6–9 days of illness.1,2
This inability to correlate PCR- positive samples with infectivity is a major limitation of the use of PCR for diagnostic purposes. Many jurisdictions require two negative PCR tests in order to allow people out of quarantine, self- isolation, or hospital. However, patients have remained PCR- positive in the respiratory tract for SARS- CoV- 2 for up to 83 days, even though no infectious virions were present.3