ABSTRACT
BackgroundAlthough nasopharyngeal (NP) samples have been considered the gold standard for COVID-19 testing, variability in viral load across different anatomical sites could theoretically cause NP samples to be less sensitive than saliva or nasal samples in certain cases. Self-collected samples also have logistical advantages over NP samples, making them amenable to population-scale screening. MethodsTo evaluate sampling alternatives for population screening, we collected NP, saliva, and nasal samples from two cohorts with varied levels and types of symptoms. ResultsIn a mixed cohort of 60 symptomatic and asymptomatic participants, we found that saliva had 88% concordance with NP when tested in the same testing lab (n = 41), and 68% concordance when tested in different testing labs (n = 19). In a second cohort of 20 participants hospitalized for COVID-19, saliva had 74% concordance with NP tested in the same testing lab, but detected virus in two participants that tested negative with NP on the same day. Medical record review showed that the saliva-based testing sensitivity was related to the timing of symptom onset and disease stage. ConclusionsWe find that no sample site will be perfectly sensitive for COVID-19 testing in all situations, and the significance of negative results will always need to be determined in the context of clinical signs and symptoms. Saliva retained high clinical sensitivity while allowing easier collection, minimizing the exposure of healthcare workers and need for personal protective equipment, and making it a viable option for population-scale testing.
ABSTRACT
The global COVID-19 pandemic has led to an urgent need for scalable methods for clinical diagnostics and viral tracking. Next generation sequencing technologies have enabled large-scale genomic surveillance of SARS-CoV-2 as thousands of isolates are being sequenced around the world and deposited in public data repositories. A number of methods using both short- and long-read technologies are currently being applied for SARS-CoV-2 sequencing, including amplicon approaches, metagenomic methods, and sequence capture or enrichment methods. Given the small genome size, the ability to sequence SARS-CoV-2 at scale is limited by the cost and labor associated with making sequencing libraries. Here we describe a low-cost, streamlined, all amplicon-based method for sequencing SARS-CoV-2, which bypasses costly and time-consuming library preparation steps. We benchmark this tailed amplicon method against both the ARTIC amplicon protocol and sequence capture approaches and show that an optimized tailed amplicon approach achieves comparable amplicon balance, coverage metrics, and variant calls to the ARTIC v3 approach and represents a cost-effective and highly scalable method for SARS-CoV-2 sequencing.
ABSTRACT
The COVID-19 global pandemic is an unprecedented health emergency. Insufficient access to testing has hampered effective public health interventions and patient care management in a number of countries. Furthermore, the availability of regulatory-cleared reagents has challenged widespread implementation of testing. We rapidly developed a qRT-PCR SARS-CoV-2 detection assay using a 384-well format and tested its analytic performance across multiple nucleic acid extraction kits. Our data shows robust analytic accuracy on residual clinical biospecimens. Limit of detection sensitivity and specificity was confirmed with currently available commercial reagents. Our methods and results provide valuable information for other high-complexity laboratories seeking to develop effective, local, laboratory-developed procedures with high-throughput capability to detect SARS-CoV-2.
