A sensitive and affordable multiplex RT-qPCR assay for SARS-CoV-2 detection

With the ongoing COVID-19 pandemic, caused by the novel coronavirus SARS-CoV-2, there is need for sensitive, specific and affordable diagnostic tests to identify infected individuals, not all of whom are symptomatic. The most sensitive test involves the detection of viral RNA using RT-qPCR, with many commercial kits now available for this purpose. However, these are expensive and supply of such kits in sufficient numbers cannot always be guaranteed. We therefore developed a multiplex assay using well-established SARS-CoV-2 targets alongside a human cellular control ( RPP30 ) and a viral spike-in control (PhHV-1), which monitor sample quality and nucleic acid extraction efficiency respectively. Here, we establish that this test performs as well as widely used commercial assays, but at substantially reduced cost. Furthermore, we demonstrate >1,000-fold variability in material routinely collected by nose-and-throat swabbing, and establish a statistically significant correlation between the detected level of human and SARS-CoV-2 nucleic acids. The inclusion of the human control probe in our assay therefore provides a quantitative measure of sample quality that could help reduce false negative rates. We demonstrate feasibility of establishing a robust RT-qPCR assay at ∼10% of the cost of equivalent commercial assays, which could benefit low resource environments and make high volume testing more affordable.