scholarly journals Saliva Is Comparable to Nasopharyngeal Swabs for Molecular Detection of SARS-CoV-2

Author(s):  
Cody Callahan ◽  
Sarah Ditelberg ◽  
Sanjucta Dutta ◽  
Nancy Littlehale ◽  
Annie Cheng ◽  
...  

AbstractBackgroundThe continued need for molecular testing for SARS-CoV-2 and potential for self-collected saliva as an alternative to nasopharyngeal (NP) swabs for sample acquisition led us to compare saliva to NP swabs in an outpatient setting, without restrictions to avoid food, drink, smoking, or tooth-brushing.MethodsA total of 385 pairs of NP and saliva specimens were obtained, the majority from individuals presenting for initial evaluation, and were tested on two high-sensitivity RT-PCR platforms: the Abbott m2000 and Abbott Alinity m (both with limits of detection [LoD] of 100 copies of viral RNA/mL).ResultsConcordance between saliva and NP was excellent overall (Cohen’s κ=0.93), for both initial and followup testing, for both platforms, and for specimens treated with guanidinium transport medium as preservative as well as for untreated saliva (κ=0.88-0.95). Viral loads were on average 16x higher in NP specimens than saliva specimens, suggesting that only the relatively small fraction of outpatients (∼8% in this study) who present with very low viral loads (<1,600 copies/mL from NP swabs) would be missed by testing saliva instead of NP swabs, when using sensitive testing platforms. Special attention was necessary to ensure leak-resistant specimen collection and transport.ConclusionsThe advantages of self-collection of saliva, without behavioral restrictions, will likely outweigh a minor potential decrease in clinical sensitivity in individuals less likely to pose an infectious risk to others for many real-world scenarios, especially for initial testing.Key pointsSaliva has comparable sensitivity and specificity to nasopharyngeal swabs for RT-PCR-based COVID-19 testing (concordance, κ=0.93; n=385 participants), albeit with slightly lower recovery of viral RNA. Treatment with a readily available guanidinium preservative within 24 hours of sample collection improves recovery.

Diagnostics ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 363
Author(s):  
Vânia M. Moreira ◽  
Paulo Mascarenhas ◽  
Vanessa Machado ◽  
João Botelho ◽  
José João Mendes ◽  
...  

The rapid and accurate testing of SARS-CoV-2 infection is still crucial to mitigate, and eventually halt, the spread of this disease. Currently, nasopharyngeal swab (NPS) and oropharyngeal swab (OPS) are the recommended standard sampling techniques, yet, these have some limitations such as the complexity of collection. Hence, several other types of specimens that are easier to obtain are being tested as alternatives to nasal/throat swabs in nucleic acid assays for SARS-CoV-2 detection. This study aims to critically appraise and compare the clinical performance of RT-PCR tests using oral saliva, deep-throat saliva/posterior oropharyngeal saliva (DTS/POS), sputum, urine, feces, and tears/conjunctival swab (CS) against standard specimens (NPS, OPS, or a combination of both). In this systematic review and meta-analysis, five databases (PubMed, Scopus, Web of Science, ClinicalTrial.gov and NIPH Clinical Trial) were searched up to the 30th of December, 2020. Case-control and cohort studies on the detection of SARS-CoV-2 were included. The methodological quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS 2). We identified 1560 entries, 33 of which (1.1%) met all required criteria and were included for the quantitative data analysis. Saliva presented the higher accuracy, 92.1% (95% CI: 70.0–98.3), with an estimated sensitivity of 83.9% (95% CI: 77.4–88.8) and specificity of 96.4% (95% CI: 89.5–98.8). DTS/POS samples had an overall accuracy of 79.7% (95% CI: 43.3–95.3), with an estimated sensitivity of 90.1% (95% CI: 83.3–96.9) and specificity of 63.1% (95% CI: 36.8–89.3). The remaining index specimens could not be adequately assessed given the lack of studies available. Our meta-analysis shows that saliva samples from the oral region provide a high sensitivity and specificity; therefore, these appear to be the best candidates for alternative specimens to NPS/OPS in SARS-CoV-2 detection, with suitable protocols for swab-free sample collection to be determined and validated in the future. The distinction between oral and extra-oral salivary samples will be crucial, since DTS/POS samples may induce a higher rate of false positives. Urine, feces, tears/CS and sputum seem unreliable for diagnosis. Saliva testing may increase testing capacity, ultimately promoting the implementation of truly deployable COVID-19 tests, which could either work at the point-of-care (e.g. hospitals, clinics) or at outbreak control spots (e.g., schools, airports, and nursing homes).


PLoS ONE ◽  
2021 ◽  
Vol 16 (6) ◽  
pp. e0252687
Author(s):  
Sukalyani Banik ◽  
Kaheerman Saibire ◽  
Shraddha Suryavanshi ◽  
Glenn Johns ◽  
Soumitesh Chakravorty ◽  
...  

Background Upper respiratory samples used to test for SARS-CoV-2 virus may be infectious and present a hazard during transport and testing. A buffer with the ability to inactivate SARS-CoV-2 at the time of sample collection could simplify and expand testing for COVID-19 to non-conventional settings. Methods We evaluated a guanidium thiocyanate-based buffer, eNAT™ (Copan) as a possible transport and inactivation medium for downstream Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) testing to detect SARS-CoV-2. Inactivation of SARS-CoV-2 USA-WA1/2020 in eNAT and in diluted saliva was studied at different incubation times. The stability of viral RNA in eNAT was also evaluated for up to 7 days at room temperature (28°C), refrigerated conditions (4°C) and at 35°C. Results SARS-COV-2 virus spiked directly in eNAT could be inactivated at >5.6 log10 PFU/ml within a minute of incubation. When saliva was diluted 1:1 in eNAT, no cytopathic effect (CPE) on VeroE6 cells was observed, although SARS-CoV-2 RNA could be detected even after 30 min incubation and after two cell culture passages. A 1:2 (saliva:eNAT) dilution abrogated both CPE and detectable viral RNA after as little as 5 min incubation in eNAT. SARS-CoV-2 RNA from virus spiked at 5X the limit of detection remained positive up to 7 days of incubation in all tested conditions. Conclusion eNAT and similar guanidinium thiocyanate-based media may be of value for transport, stabilization, and processing of clinical samples for RT-PCR based SARS-CoV-2 detection.


Author(s):  
Varunika Vijayvergia ◽  
Aruna Vyas ◽  
Nazneen Pathan ◽  
Rajni Sharma ◽  
Snigdha Purohit ◽  
...  

Introduction: Coronavirus Disease 2019 (COVID-19) has been haunting the world since December 2019 and has grown to pandemic proportions from March 2020. Even after a full year of research and study, the most effective way to control the spread of this infection is early diagnosis and isolation of the cases. Real-time Reverse Transcription Polymerase Chain Reaction (RT-PCR) is considered the standard test all over the world for the diagnosis of Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2) infection. All the sample collection guidelines have recommended stringent maintenance of the cold chain for the sample transport. However, it is not possible for the resource constrained developing countries with inadequate infrastructure to comply with these guidelines all the time. Aim: To determine necessity of stringent transport criteria and the effect of temperature on the clinical sensitivity of a RT-PCR assay for diagnosis of SARS-CoV-2 infection. Materials and Methods: In this prospective experimental study conducted in November 2020, 49 positive samples were kept at ambient room temperature and were tested everyday with RT- PCR for the detection of SARS-CoV-2 Ribonucleic Acid (RNA). The samples were also kept under refrigeration at 4°C and were also tested by RT-PCR and the results were compared with their respective counterparts kept at room temperature till nine days. Python Jupiter notebook SciPy and Anaconda software was used for statistical analysis. Results: It was observed that the positivity of the RT-PCR results were not deteriorated till five days and there was no significant deterioration even after nine days of samples being stored at room temperature suggesting that even if the viral RNA itself is not stable outside strict temperature control but small fragment or target genetic sequences are enough for detection of virus by RT-PCR. Conclusion: It is possible to keep samples at this ambient temperature for five days without any loss of positivity in RT-PCR.


2022 ◽  
Author(s):  
Kristie J Sun ◽  
Mary Jane E Vaeth ◽  
Matthew L Robinson ◽  
Maryam Elhabashy ◽  
Ishaan Gupta ◽  
...  

SARS-CoV-2 continues to develop new, increasingly infectious variants, such as delta and omicron. Here, we evaluate the efficacy of the Abbott BinaxNOW Rapid Antigen Test against the gold standard of Reverse Transcription Polymerase Chain Reaction (RT-PCR) in 1054 pediatric participants presenting to a state-owned high-volume Coronavirus Disease 2019 (COVID-19) testing site. During the testing period, the delta variant was predominant. Prior to sample collection, symptomatic and exposure status was collected for all participants based on Centers for Disease Control (CDC) criteria. RT-PCR results demonstrated an overall prevalence rate of 5.2%. For all participants, the sensitivity of the rapid antigen tests was 92.7% (95% CI 82.4% - 98.0%) and specificity was 98.0% (95% CI 97.0%-98.8%). For symptomatic participants, the sensitivity was 92.3% (95% CI 74.9% - 99.1%), specificity was 96.6% (95% CI 93.6%- 98.4%), positive predictive value (PPV) was 72.7% (95% CI 54.5% - 86.7%) and negative predictive value (NPV) was 99.2% (95% CI 98.2% - 100%). Among asymptomatic participants, the sensitivity was 92.6% (95% CI 75.7% - 99.1%), specificity was 98.6% (95% CI 97.5% - 99.3%) the PPV was 71.4% (95% CI 53.7% - 85.4%) and the NPV was 99.7% (95% CI 99.0% - 100%). Our reported sensitivity and NPV are higher than other pediatric studies, but specificity and PPV are lower. Importance Children are especially impacted by the disease and its ability to disrupt educational opportunities. Although vaccinations have been approved for children 5 years and older, many children remain unvaccinated. Widespread testing may improve the ability for children to remain in in-person activities, minimizing absences from school and extracurriculars. Highly accurate rapid antigen tests may be vital to containing future COVID-19 waves while mitigating detrimental effects.


2021 ◽  
Author(s):  
Nira R. Pollock ◽  
Jesica R. Jacobs ◽  
Kristine Tran ◽  
Amber Cranston ◽  
Sita Smith ◽  
...  

AbstractBackgroundRapid diagnostic tests (RDTs) for SARS-CoV-2 antigens (Ag) that can be performed at point-of-care (POC) can supplement molecular testing and help mitigate the COVID-19 pandemic. Deployment of an Ag RDT requires an understanding of its operational and performance characteristics under real-world conditions and in relevant subpopulations. We evaluated the Abbott BinaxNOW™ COVID-19 Ag Card in a high-throughput, drive-through, free community testing site in Massachusetts (MA) using anterior nasal (AN) swab RT-PCR for clinical testing.MethodsIndividuals presenting for molecular testing in two of seven lanes were offered the opportunity to also receive BinaxNOW testing. Dual AN swabs were collected from symptomatic and asymptomatic children (≤ 18 years) and adults. BinaxNOW testing was performed in a testing pod with temperature/humidity monitoring. One individual performed testing and official result reporting for each test, but most tests had a second independent reading to assess inter-operator agreement. Positive BinaxNOW results were scored as faint, medium, or strong. Positive BinaxNOW results were reported to patients by phone and they were instructed to isolate pending RT-PCR results. The paired RT-PCR result was the reference for sensitivity and specificity calculations.ResultsOf 2482 participants, 1380 adults and 928 children had paired RT-PCR/BinaxNOW results and complete symptom data. 974/1380 (71%) adults and 829/928 (89%) children were asymptomatic. BinaxNOW had 96.5% (95% confidence interval [CI] 90.0-99.3) sensitivity and 100% (98.6-100.0) specificity in adults within 7 days of symptoms, and 84.6% (65.1-95.6) sensitivity and 100% (94.5-100.0) specificity in children within 7 days of symptoms. Sensitivity and specificity in asymptomatic adults were 70.2% (56.6-81.6) and 99.6% (98.9-99.9), respectively, and in asymptomatic children were 65.4% (55.6-74.4) and 99.0% (98.0-99.6), respectively. By cycle threshold (Ct) value cutoff, sensitivity in all subgroups combined (n=292 RT-PCR-positive individuals) was 99.3% with Ct ≤25, 95.8% with ≤30, and 81.2% with ≤35. Twelve false positive BinaxNOW results (out of 2308 tests) were observed; in all twelve, the test bands were faint but otherwise normal, and were noted by both readers. One invalid BinaxNOW result was identified. Inter-operator agreement (positive versus negative BinaxNOW result) was 100% (n = 2230/2230 double reads). Each operator was able to process 20 RDTs per hour. In a separate set of 30 specimens (from individuals with symptoms ≤7 days) run at temperatures below the manufacturer’s recommended range (46-58.5°F), sensitivity was 66.7% and specificity 95.2%.ConclusionsBinaxNOW had very high specificity in both adults and children and very high sensitivity in newly symptomatic adults. Overall, 95.8% sensitivity was observed with Ct ≤ 30. These data support public health recommendations for use of the BinaxNOW test in adults with symptoms for ≤7 days without RT-PCR confirmation. Excellent inter-operator agreement indicates that an individual can perform and read the BinaxNOW test alone. A skilled laboratorian can perform and read 20 tests per hour. Careful attention to temperature is critical.


2021 ◽  
Author(s):  
Sukalyani Banik ◽  
Kaheerman Saibire ◽  
Shraddha Suryavanshi ◽  
Glenn Johns ◽  
Soumitesh Chakravorty ◽  
...  

AbstractBackgroundUpper respiratory samples used to test for SARS-CoV-2 virus may be infectious and present a hazard during transport and testing. A buffer with the ability to inactivate SARS-CoV-2 at the time of sample collection could simplify and expand testing for COVID-19 to non-conventional settings.MethodsWe evaluated a guanidium thiocyanate-based buffer, eNAT™ (Copan) as a possible transport and inactivation medium for downstream RT-PCR testing to detect SARS-CoV-2. Inactivation of SARS-CoV-2 USA-WA1/2020 in eNAT and in diluted saliva was studied at different incubation times. The stability of viral RNA in eNAT was also evaluated for up to 7 days at room temperature (28°C), refrigerated conditions (4°C) and at 35°C.ResultsSARS-COV-2 virus spiked directly in eNAT could be inactivated at >5.6 log10 PFU/ml within a minute of incubation. When saliva was diluted 1:1 in eNAT, no cytopathic effect (CPE) on vero-E6 cell lines was observed, although SARS-CoV-2 RNA could be detected even after 30 min incubation and after two cell culture passages. A 1:2 (saliva:eNAT) dilution abrogated both CPE and detectable viral RNA after as little as 5 min incubation in eNAT. SARS-CoV-2 RNA from virus spiked at 5X the limit of detection remained positive up to 7 days of incubation in all tested conditions.ConclusioneNAT and similar guanidinium thiocyanate-based media may be of value for transport, preservation, and processing of clinical samples for RT-PCR based SARS-CoV-2 detection.


Author(s):  
Remco de Kock ◽  
Mieke Baselmans ◽  
Volkher Scharnhorst ◽  
Birgit Deiman

Abstract The purpose of this study is to develop a one-step droplet digital RT-PCR (RT-ddPCR) multiplex assay that allows for sensitive quantification of SARS-CoV-2 RNA with respect to human-derived RNA and could be used for screening and monitoring of Covid-19 patients. A one-step RT-ddPCR multiplex assay was developed for simultaneous detection of SARS-CoV-2 E, RdRp and N viral RNA, and human Rpp30 DNA and GUSB mRNA, for internal nucleic acid (NA) extraction and RT-PCR control. Dilution series of viral RNA transcripts were prepared in water and total NA extract of Covid-19-negative patients. As reference assay, an E-GUSB duplex RT-PCR was used. GUSB mRNA detection was used to set validity criteria to assure viral RNA and RT-PCR assay quality and to enable quantification of SARS-CoV-2 RNA. In a background of at least 100 GUSB mRNA copies, 5 copies of viral RNA are reliably detectable and 10 copies viral RNA copies are reliably quantifiable. It was found that assay sensitivity of the RT-ddPCR was not affected by the total NA background while assay sensitivity of the gold standard RT-PCR assay is drastically decreased when SARS-CoV-2 copies were detected in a background of total NA extract compared with water. The present study describes a robust and sensitive one-step ddRT-PCR multiplex assay for reliable quantification of SARS-CoV-2 RNA. By determining the fractional abundance of viral RNA with respect to a human housekeeping gene, viral loads from different samples can be compared, what could be used to investigate the infectiveness and to monitor Covid-19 patients.


2021 ◽  
Author(s):  
Noah Toppings ◽  
Abu Mohon ◽  
Yoonjung Lee ◽  
Hitendra Kumar ◽  
Daniel Lee ◽  
...  

Abstract The highly infectious nature of SARS-CoV-2 necessitates the use of widespread testing to control the spread of the virus. Presently, the standard molecular testing method (reverse transcriptase-polymerase chain reaction, RT-PCR) is restricted to the laboratory, time-consuming, and costly. This increases the turnaround time for getting test results. The study sought to develop a rapid, near-patient saliva-based test for COVID-19 with similar accuracy to that of standard RT-PCR tests. A lyophilized dual-target reverse transcription-loop-mediated isothermal amplification (RT-LAMP) test with fluorometric detection by the naked eye. The assay relies on dry reagents that are room temperature stable. A device containing a centrifuge, heat block, and blue LED light system was manufactured to reduce the cost of performing the assay. This test has a limit of detection of 1 copy/µL and achieved positive percent agreement of 100% [95% CI 88.43% to 100.0%] and negative percent agreement of 96.7% [95% CI 82.78% to 99.92%] on saliva. Saliva-Dry LAMP can be completed in 105 minutes. Precision, cross-reactivity, and interfering substances analysis met international regulatory standards. The combination of ease of sample collection, dry reagents, visual detection, low capital equipment cost, and excellent analytical sensitivity make Saliva-Dry LAMP particularly useful for resource-limited settings.


Author(s):  
Cody Callahan ◽  
Rose A. Lee ◽  
Ghee Rye Lee ◽  
Kate Zulauf ◽  
James E. Kirby ◽  
...  

The urgent need for large-scale diagnostic testing for SARS-CoV-2 has prompted interest in sample-collection methods of sufficient sensitivity to replace nasopharynx (NP) sampling. Nasal-swab samples are an attractive alternative; however, previous studies have disagreed over how nasal sampling performs relative to NP sampling. Here, we compared nasal vs. NP specimens collected by healthcare workers in a cohort of individuals clinically suspected of COVID-19 as well as SARS-CoV-2 RT-PCR positive outpatients undergoing follow-up. We compared subjects being seen for initial evaluation vs. follow-up, two different nasal-swab collection protocols, and three different transport conditions, including traditional viral transport media (VTM) and dry swabs, on 307 total study participants. We compared categorical results and viral loads to those from standard NP swabs collected at the same time from the same patients. All testing was performed by RT-PCR on the Abbott SARS-CoV-2 RealTime EUA (limit of detection [LoD], 100 copies viral genomic RNA/mL transport medium). We found low concordance overall, with Cohen’s kappa of 0.49, with high concordance only for subjects with very high viral loads. We found medium concordance for testing at initial presentation (κ=0.68), and very low concordance for followup testing (κ=0.27). Finally, we show that previous reports of high concordance may have resulted from measurement using assays with sensitivity ≥1,000 copies/mL. These findings suggest nasal-swab testing be used for situations in which viral load is expected to be high, as we demonstrate that nasal-swab testing is likely to miss patients with low viral loads.


2020 ◽  
Author(s):  
Masateru Taniguchi ◽  
Shohei Minami ◽  
Chikako Ono ◽  
Rina Hamajima ◽  
Ayumi Morimura ◽  
...  

Abstract High-throughput, high-accuracy detection of emerging viruses allows for pandemic prevention and control. Currently, reverse transcription-polymerase chain reaction (RT-PCR) is used to diagnose the presence of SARS-CoV-2. The principle of the test is to detect RNA in the virus using a pair of primers that specifically binds to the base sequence of the viral RNA. However, RT-PCR is a sophisticated technique requiring a time-consuming pretreatment procedure for extracting viral RNA from clinical specimens and to obtain high sensitivity. Here, we report a method for detecting novel coronaviruses with high sensitivity using artificial intelligent nanopores utilizing a simple procedure that does not require RNA extraction. Artificial intelligent nanopore platform consists of machine learning software on the servers, portable high-speed and high-precision current measuring instrument, and scalable, cost-effective semiconducting nanopore modules. Here we show that the artificial intelligent nanopores are successful in accurate identification of four types of coronaviruses, HCoV-229E, SARS-CoV, MERS-CoV, and SARS-CoV-2, which are usually extremely difficult to detect. The positive/negative diagnostics of the new coronavirus is achieved with a sensitivity of 95 % and specificity of 92 % with a 5-minute diagnosis. The platform enables high throughput diagnostics with low false negatives for the novel coronavirus.


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