Researchers have designed a testing protocol for SARS-CoV-2 that can process tens of thousands of samples in less than 48 hours. The test, called SARSeq, or Saliva Analysis by RNA sequencing, achieves the same sensitivity as regular PCR tests. It can run in parallel to existing diagnostics, while being independent of the bottlenecks in supply chains. Therefore, it does not compete with other testing methods for reagents or equipment.
The testing principle is conceptually simple: individual patient samples are collected into the wells of a testing plate — one well for each sample. Then, a fragment of viral RNA unique to SARS-CoV-2 — the nucleocapsid gene — is selectively converted to DNA and PCR-amplified in any well that contains it.
What distinguishes this first step to the usual PCR test is that each sample receives a unique set of short DNA sequences — or barcodes — that attach to the amplifying viral DNA. In a second amplification step, all the samples from one plate are pooled into one well, which receives a second set of unique DNA barcodes. The contents of multiple plates can be pooled once more, as the DNA molecules from each sample carry a unique combination of two sets of barcodes. This pooling and barcoding strategy makes SARSeq highly specific and scalable.
The principles behind SARSeq are simple and adaptable to any respiratory pathogen. As the world’s population skyrockets along with our proximity to animals, cutting-edge diagnostic methods like SARSeq will be crucial to prevent future diseases from spreading like wildfire.