Respiratory Viral Sequencing Panel identifies SARS-CoV-2 variants, transmission and other co-circulating viruses in Georgia, USA: A Diagnostic and Epidemiologic Tool for Mass Surveillance in COVID-19 Pandemic (preprint)

Background In the current phase of COVID-19 pandemic, we are facing two serious public health challenges that include deficits in SARS-CoV-2 variant monitoring, and neglect of other co-circulating respiratory viruses. Additionally, accurate assessment of the evolution, extent and dynamics of the outbreak are required to understand the transmission of the virus amongst seemingly unrelated cases and provide critical epidemiological information. To address these challenges, we evaluated a new high-throughput next-generation sequencing (NGS), respiratory viral panel (RVP) that includes 40 viral pathogens with the aim of analyzing viral subtypes, mutational variants of SARS-CoV-2, model to understand the spread of the virus in the state of Georgia, USA, and to assess other circulating viruses in the same population. Methods This study evaluated a total of 522 samples that included 483 patient samples and 42 synthetic positive control material. The performance metrics were calculated for both clinical and reference control samples by comparing detection results with the RT-PCR assay. The limit of detection (LoD) studies were conducted as per the FDA guidelines. Inference and visualization of the phylogeny of the SARS-CoV-2 sequences were performed through the Nextstrain Command-Line Interface (CLI) tool, utilizing the associated augur and auspice toolkits. Results The performance metrics calculated using both the clinical samples and the reference controls revealed a PPA, NPA and accuracy of 95.98%, 85.96% and 94.4%, respectively. The LoD was determined to be 10 copies/ml with all 25 replicates detected across two different runs. The clade for pangolin lineage B that contains certain distant variants, including P4715L in ORF1ab, Q57H in ORF 3a and, S84L in ORF8 covarying with the D614G spike protein mutation were the most prevalent, early in the pandemic, in Georgia, USA. In our analysis, isolates from the same county formed paraphyletic groups, which indicated virus transmission between counties. Conclusion The study demonstrates the clinical and public health utility of the NGS-RVP to identify novel variants that can provide actionable information to prevent or mitigate emerging viral threats, models that provide insights into viral transmission patterns and predict transmission/ resurgence of regional outbreaks and provide critical information on co-circulating respiratory viruses that might be independent factors contributing to the global disease burden.

A Novel Multiplex PCR Based Detection Assay Using Saliva or Nasopharyngeal Samples for SARS-Cov-2, Influenza A and B: Clinical Validation and Utility for Mass Surveillance. (preprint)

BackgroundThe COVID-19 pandemic has resulted in a significant diversion of human and material resources to COVID-19 diagnostics, to the extent that testing of viral pathogens normally contributing to seasonal respiratory tract infections have been markedly neglected. The global health burden due to influenza viruses and co-infection in COVID-19 patients remains undocumented but clearly pose serious public health consequences. To address these clinical and technical challenges, we have optimized and validated a highly sensitive RT-PCR based multiplex assay for the detection of SARS-CoV-2, Influenza A and B viruses in a single test. MethodsThis study evaluated clinical specimens (n=1411) that included 1019 saliva and 392 nasopharyngeal swab (NPS) samples collected in either healthcare or community setting. Samples were tested using two assays: FDA-EUA approved SARS-CoV-2 assay that targets N and ORF1ab gene, and the PKamp RT-PCR based assay that targets SARS-CoV-2, Influenza viruses A and B. The limit of detection (LoD) studies was conducted as per the FDA guidelines using SARS-CoV-2 and Influenza A and B reference control materials. ResultsOf the 1019 saliva samples, 17.0% (174/1019) tested positive for SARS-CoV-2 using either assay. The detection rate for SARS-CoV-2 was higher with our multiplex assay compared to SARS-specific assay [91.9% (160/174) vs. 87.9% (153/174)], respectively. Of the 392 NPS samples, 10.4% (41/392) tested positive for SARS-CoV-2 using either assay. The detection rate for SARS-CoV-2 was higher with our multiplex assay compared to SARS-specific assay [97.5% (40/41) vs. 92.1% (39/41)], respectively. The Ct values for SARS-CoV-2 were comparable between the two assays, whereas the Ct values of the housekeeping gene was significantly lower with multiplex assay compared to SARS-specific assay. The LoD was established as 60 copies/ml for SARS-CoV-2 and 180 copies/ml for Influenza A and B viruses for both saliva and NPS samples. ConclusionThis study presents clinical validation of a multiplex PCR assay for testing SARS-CoV-2, Influenza A and B viruses, using NPS and saliva samples, and demonstrates the feasibility of implementing the assay without disrupting the existing laboratory workflow. This novel assay uses the same instruments, sample types, supplies, and laboratory personnel as needed for the testing of SARS-CoV-2 virus.

SalivaSTAT: Direct-PCR and pooling of saliva samples collected in healthcare and community setting for SARS-CoV-2 mass surveillance. (preprint)

BackgroundThe limitations of widespread current COVID-19 diagnostic testing lie at both pre-analytical and analytical stages. Collection of nasopharyngeal swabs is invasive and is associated with exposure risk, high cost, and supply-chain constraints. Additionally, the RNA extraction in the analytical stage is the most significant rate-limiting step in the entire testing process. To alleviate these limitations, we developed a universal saliva processing protocol (SalivaSTAT) that would enable an extraction free RT-PCR test using any of the commercially available RT-PCR kits. MethodsWe optimized saliva collection devices, heat-shock treatment and homogenization. The effect of homogenization on saliva samples for extraction-free RT-PCR assay was determined by evaluating samples with and without homogenization and preforming viscosity measurements. Saliva samples (872) previously tested using the FDA-EUA method were reevaluated with the optimized SalivaSTAT protocol using two widely available commercial RT-PCR kits. Further, a five-sample pooling strategy was evaluated as per FDA guidelines using the SalivaSTAT protocol. ResultsThe saliva collection (done without any media) performed comparable to the FDA-EUA method. The SalivaSTAT protocol was optimized by incubating saliva samples at 95{degrees}C for 30-minutes and homogenization, followed by RT-PCR assay. The clinical sample evaluation of 630 saliva samples using the SalivaSTAT protocol with PerkinElmer (600-samples) and CDC (30-samples) RT-PCR assay achieved positive (PPA) and negative percent agreement (NPA) of 95.8% and 100%, respectively. The LoD was established as [~]20-60 copies/ml by absolute quantification. Further, a five-sample pooling evaluation using 250 saliva samples achieved a PPA and NPA of 92% and 100%, respectively. ConclusionWe have optimized an extraction-free direct RT-PCR assay for saliva samples that demonstrated comparable performance to FDA-EUA assay (Extraction and RT-PCR). The SalivaSTAT protocol is a rapid, sensitive, and cost-effective method that can be adopted globally, and has the potential to meet testing needs and may play a significant role in management of the current pandemic.

SalivaAll: Clinical validation of a sensitive test for saliva collected in healthcare and community settings with pooling utility for SARS-CoV-2 mass surveillance. (preprint)

Background: The adoption of saliva as a specimen type for SARS-CoV-2 mass surveillance can significantly increase population compliance with decreased exposure risk for healthcare workers. However, studies evaluating the clinical performance of saliva compared to nasopharyngeal swab (NPS) samples have demonstrated conflicting results regardless of the collection being in healthcare or community settings. Further, pooled testing with saliva remains a challenge owing to the ambiguous sensitivity, limit of detection (LoD), and processing challenges. To overcome these limitations, SalivaAll protocol was developed and validated as a cost-effective measure that must be used on saliva collected in health care or community settings with pooling utility for SARS-CoV-2 mass surveillance. Methods: The study evaluated 429 matched NPS and saliva samples collected from 344 individuals in either healthcare or community setting. In phase I (protocol U), 240 matched NPS, and saliva samples were tested for SARS-CoV-2 detection by RT-PCR. In phase II (SalivaAll protocol), 189 matched NPS and saliva samples were tested, with an additional sample homogenization step for saliva before RNA extraction, followed by RT-PCR. Eighty-five saliva samples were evaluated with both protocols (U and SalivaAll). Subsequently, adopting SalivaAll protocol, a five-sample pooling strategy was evaluated for saliva samples based on FDA recommendations. Results: In phase I, 28.3% (68/240) samples tested positive for SARS-CoV-2 from either saliva, NPS, or both. The detection rate was lower in saliva compared to NPS samples (50.0% vs. 89.7%). In phase II, 50.2% (95/189) samples tested positive for SARS-CoV-2 from either saliva, NPS, or both. The detection rate for SARS-CoV-2 was higher in saliva compared to NPS testing (97.8% vs. 78.9%). Of the 85 saliva samples evaluated by both protocols, 57.6% (49) tested positive for SARS-CoV-2 with either protocol U, SalivaAll, or both. The detection rate was 100% for samples tested with SalivaAll, whereas it was 36.7% with protocol U. Also, the LoD with SalivaAll protocol was 20 copies/ml. The pooled testing approach demonstrated a 95% positive and 100% negative percent agreement. Conclusion: This single-site study demonstrated the variability of results reported in the literature for saliva samples, and found that the discrepancies are explained by processing challenges associated with saliva samples. We have optimized a protocol for saliva samples that results in higher sensitivity compared to NPS samples and also breaks the barrier to using pooled saliva testing for SARS-CoV-2.

Clinical validation of innovative, low cost, kit-free, RNA processing protocol for RT-PCR based COVID-19 testing. (preprint)

The current gold-standard molecular diagnosis for COVID-19 is based on a multi-step assay involving RNA-extraction and RT-PCR analysis for the detection of SARS-CoV-2. RNA-extraction step has been a major rate-limiting step in implementing high-throughput screening for COVID-19 during this pandemic. Moreover, clinical laboratories are facing several challenges that include cost, reagents, instrumentation, turn-around time, trained personnel, and supply-chain constraints to efficiently implement and sustain testing. Cognizant of these limitations, we evaluated the extraction-free methods described in the literature and have developed an innovative, simplified and easy protocol employing limited reagents to extract RNA for subsequent RT-PCR analysis. Nasopharyngeal-swab samples were subjected to the following individual conditions: 65{degrees}C for 15 minutes; 80{degrees}C for 5 minutes; 90{degrees}C for 5 minutes or 80{degrees}C for 1 minute, and processed for direct RT-PCR. These groups were also compared with a supplemental protocol adding isopropanol-ethanol-water elution steps followed by RT-PCR assay. The direct RT-PCR assay did not detect SARS-CoV-2 within the various temperature incubation only groups, whereas, the 90{degrees}C for 5 minutes-isopropanol-ethanol-water method was found to be comparable to the FDA-EUA method. Evaluation of the performance metrics for 100 clinical samples demonstrated a sensitivity of 94.2% and a specificity of 100%. The limit of detection was ascertained to be ~40 copies/ml by absolute-quantification. The protocol presented for this assay employs limited reagents and yields results with high sensitivity. Additionally, it presents a simplified methodology that would be easier to implement in laboratories in limited resource countries in order to meet the high current COVID-19 testing needs.