The COVID-19 pandemic has emphasized the inability of diagnostic laboratories' testing capacity to keep up with the surging demand. The primary reasons were the lack of reagents (e.g., viral transport media and nucleic acid extraction kits) and the low throughput of the gold-standard molecular detection method (RT-qPCR). While the reagent shortages were eventually resolved, the limited throughput of the RT-qPCR remains a bottleneck for high-throughput testing applications even today.
Here, we introduce a rapid saliva-based extraction-free molecular assay, which utilizes a non-invasive saliva sampling and extraction-free sample preparation, a fast endpoint RT-PCR and a high-throughput optical modulation biosensing (ht-OMBi) detection platform. We blindly tested 364 paired nasopharyngeal swabs and saliva samples from suspected SARS-CoV-2 cases in Israel. Compared with the gold standard swab-based RT-qPCR, the presented assay's sensitivity and specificity are 90.7% and 95.3%, respectively, but is achieved with only 50 min. sample-to-result turnaround time (~60% faster than the regular RT-qPCR), allowing high throughput and considerable savings of the reagents and disposables.
KEYWORDS: Molecules, Luminescence, Magnetism, Target detection, Signal detection, Signal to noise ratio, Modulation, Diagnostics, Polymers, In vitro testing
The COVID-19 pandemic demands fast, sensitive, and specific diagnostic tools for virus surveillance and containment. Current methods for diagnosing the COVID-19 are based on direct detection of either viral antigens or viral ribonucleic acids (RNA) in swab samples. Antigen-targeting tests are simple, have fast turnaround times, and allow rapid testing. Unfortunately, compared with viral RNA-targeting tests, their sensitivity is low, especially during the initial stages of the disease, which limits their adoption and implementation. Direct detection of SARS-CoV-2 RNA using reversetranscription quantitative polymerase chain reaction (RT-qPCR) is sensitive and specific, making it a golden standard in SARS-CoV-2 detection. However, it had not seen a significant update since its introduction three decades ago. It has a long turnaround time, requires a high number of amplification cycles, and a complicated and expensive detection system for real-time monitoring of the signal. While insignificant for research applications, these limitations present severe problems for mass testing required to contain the disease. Here, we introduce a diagnostic platform for rapid and highly sensitive clinical diagnosis of COVID-19. Based on the biochemical principles of the RT-PCR, it utilizes the endpoint detection by the magnetic modulation biosensing (MMB) system, allowing the detection of as little as two copies of SARS-CoV-2 in ~30 minutes. Testing 309 RNA samples from verified SARS-CoV-2 carriers and healthy subjects resulted in 97.8% sensitivity, 100% specificity, and 0% crossreactivity. This level of performance is on par with the gold standard (RT-qPCR) but requires 1/3 of the time. The platform can be easily adapted to detect almost any other pathogen of choice.
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