Self-Collected Samples to Detect SARS-CoV-2: Direct Comparison of Saliva, Tongue Swab, Nasal Swab, Chewed Cotton Pads and Gargle Lavage

Clinical Performance of Self-Collected Purified Water Gargle for Detection of Influenza a Virus Infection by Real-Time RT-PCR

Purpose

Self-collected specimens are increasingly being used as alternatives to swab-based methods for the detection of respiratory viruses. While saliva is well accepted, gargle specimens are a potential alternative with characteristics that are more favorable for laboratory handling. This study assessed the performance of gargle specimens in the detection of influenza A viruses (IAVs).

Patients and Methods

We performed a prospective head-to-head comparison between combined nasopharyngeal and oropharyngeal swabs (NPS&OPS) and purified water gargle (PWG) among adult outpatients with febrile respiratory symptoms to detect IAVs using real-time RT-PCR during two influenza seasons.

Results

During study periods 1 (July 13 to 26, 2022, H3N2 predominated) and 2 (February 25 to March 10, 2023, H1N1 pdm09 predominated), a total of 459 patients were recruited. The overall agreement between the NPS&OPS and PWG was 85.0% (390/459, κ = 0.697), with 88.0% in period 1 and 82.6% in period 2. The detection rate of IAVs in PWG (51.6%, 237/459) was lower than that in NPS&OPS (62.3%, 286/459) (p < 0.0001). The overall sensitivity and specificity were 96.6% (93.7-98.3%) and 100% (97.1-100%) in NPS&OPS and were 80.1% (75.0-84.4%) and 100% (97.1-100%) in PWG, respectively. Among the 227 pairs of concordant positive specimens, cycle threshold (Ct) values were significantly lower in NPS&OPS than in PWG (median Ct values: 24.2, 28.2, p < 0.0001).

Conclusion

Although self-collected PWG specimens offer acceptable performance for IAVs molecular testing, NPS&OPS remain a reliable option. Given the convenience of collection, nonviscous gargles are recommended for viral detection during emergencies or under specific conditions.

Fabrication of flexible electrospinning nano-fiber membrane for detection of respiratory tract transmission virus based on SERS

The application of flexible sensors in the biomedical field is deepening. It is of great significance to develop flexible wearable sensors which are more in line with the needs of the public. A flexible polylactic acid membrane fabric was prepared by electrospinning method. The membrane was used as SERS active substrate by screen printing capture probe which combine Au nanoplates with antibodies to the target substance. Thioglycolic acid-labeled silver nanoparticles coupled with antibodies as SERS nanotags. The target substance can be fixed between the capture probe and SERS nanotags. Due to the high specific surface area between the spinning, the adhesion rate of the capture probe is higher than that of the rigid substrate, and the enrichment and hypersensitivity detection of the object to be tested could be realized. The membranes prepared are flexible, wearable, portable, highly biocompatible, and can be mass-produced for high-throughput detection. We then applied the sensor to the detection of SARS-CoV-2 with detection limits as low as 10 TU/mL. This membrane as a SERS substrate can offer a fast and non-invasive reference for the early diagnosis of respiratory infectious diseases similar to COVID-19.

Recent advances in RNA sample preparation techniques for the detection of SARS-CoV-2 in saliva and gargle

Molecular detection of SARS-CoV-2 in gargle and saliva complements the standard analysis of nasopharyngeal swabs (NPS) specimens. Although gargle and saliva specimens can be readily obtained non-invasively, appropriate collection and processing of gargle and saliva specimens are critical to the accuracy and sensitivity of the overall analytical method. This review highlights challenges and recent advances in the treatment of gargle and saliva samples for subsequent analysis using reverse transcription polymerase chain reaction (RT-PCR) and isothermal amplification techniques. Important considerations include appropriate collection of gargle and saliva samples, on-site inactivation of viruses in the sample, preservation of viral RNA, extraction and concentration of viral RNA, removal of substances that inhibit nucleic acid amplification reactions, and the compatibility of sample treatment protocols with the subsequent nucleic acid amplification and detection techniques. The principles and approaches discussed in this review are applicable to molecular detection of other microbial pathogens.

Maternal plasma and salivary anelloviruses in pregnancy and preterm birth

Introduction

Human anelloviruses, including torque teno virus (TTV) and torque teno mini virus (TTMV), are ubiquitous in the general population and have no known pathogenicity. We investigated the prevalence and viral load of TTV and TTMV in plasma and saliva over pregnancy, and assessed their association with spontaneous or medically indicated preterm birth.

Methods

This is a secondary analysis of the Measurement of Maternal Stress (MOMS) study, which recruited 744 individuals with singleton pregnancies from 4 US sites (Chicago, Pittsburgh, San Antonio, and rural Pennsylvania). Baseline outpatient visits took place in the second trimester (between 12'0 and 20'6/7  weeks' gestation), and follow-up visits in the third trimester (between 32'0 and 35'6/7  weeks' gestation). In a case-control study design, participants who delivered preterm (<37 weeks) resulting from spontaneous labor and/or preterm premature rupture of membranes ("sPTB") were compared with participants experiencing medically indicated preterm birth ("iPTB"), or delivery at term ("controls"). Plasma and saliva samples obtained during the second and third trimesters were tested for the presence and quantity of TTV and TTMV using real-time PCR. Demographic data were obtained via self-report, and clinical data via medical record review by trained research personnel.

Results

TTV was detected in plasma from 81% (second trimester) and 77% (third trimester) of participants, and in saliva from 64 and 60%. Corresponding detection rates for TTMV were 59 and 41% in plasma, and 35 and 24% in saliva. TTV and TTMV concentrations were similar between matched plasma and saliva samples. TTV prevalence and concentrations were not significantly different between groups (sPTB, iPTB, and controls). However, plasma TTMV in the third trimester was associated with sPTB and earlier gestational age at delivery. The iPTB group was not different from either the sPTB or the control group. In saliva, concentrations of TTV and TTMV were similar among the three groups. Both TTV and TTMV were more prevalent with increasing parity and were more common in Black and Hispanic participants compared to non-Hispanic White participants.

Conclusion

Anellovirus presence (specifically, TTMV) in the third trimester may be associated with preterm birth. Whether this association is causative remains to be determined.

Quantitative analysis of different respiratory specimens on two automated test systems for detection of SARS-CoV-2 RNA

Molecular testing of SARS-CoV-2 RNA is essential during the pandemic. Here, we compared the results of different respiratory specimens including anterior nasal swabs, pharyngeal swabs, saliva swabs, and gargle lavage samples to nasopharyngeal swabs on two automated SARS-CoV-2 test systems. Samples were collected and tested simultaneously from a total of 36 hospitalized symptomatic COVID-19 patients. Detection and quantification of SARS-CoV-2 was performed on cobas®6800 (Roche) and NeuMoDx™ (Qiagen) systems. Both assays showed reliable detection and quantification of SARS-CoV-2 RNA, with nasopharyngeal swabs showing the highest sensitivity. SARS-CoV-2 RNA concentrations in other respiratory specimens were lower (mean 2.5 log10 copies/ml) or even undetectable in up to 20%. These data clearly indicate that not all respiratory materials are equally suitable for the management of hospitalized patients, especially, in the late phase of COVID-19, when the viral phase subsides and inflammation becomes the predominant factor, making detection of even lower viral loads increasingly important.

Evaluation of Non-Invasive Gargle Lavage Sampling for the Detection of SARS-CoV-2 Using rRT-PCR or Antigen Assay

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused considerable disruption worldwide. For efficient SARS-CoV-2 detection, new methods of rapid, non-invasive sampling are needed. This study aimed to investigate the stability of SARS-CoV-2 in a novel medium for gargle-lavage (GL) self-sampling and to compare the performance of SARS-CoV-2 detection in paired self-collected GL and clinician-obtained nasopharyngeal swab (NPS) samples. The stability study for SARS-CoV-2 preservation in a novel medium was performed over 14 days (4 °C, 24-27 °C, and 37 °C). In total, 494 paired GL and NPS samples were obtained at the University Hospital in Olomouc in April 2021. SARS-CoV-2 detection in paired samples was performed with a SARS-CoV-2 Nucleic Acid Detection Kit (Zybio, Chongqing Municipality, Chongqing, China), an Elecsys^® SARS-CoV-2 Antigen assay (Roche Diagnostics, Mannheim, Germany), and a SARS-CoV-2 Antigen ELISA (EUROIMMUN, Lübeck, Germany). The stability study demonstrated excellent SARS-CoV-2 preservation in the novel medium for 14 days. SARS-CoV-2 was detected in 55.7% of NPS samples and 55.7% of GL samples using rRT-PCR, with an overall agreement of 91.9%. The positive percent agreement (PPA) of the rRT-PCR in the GL samples was 92.7%, and the negative percent agreement (NPA) was 90.9%, compared with the NPS samples. The PPA of the rRT-PCR in the NPS and GL samples was 93.2% when all positive tests were used as the reference standard. Both antigen detection assays showed poor sensitivity compared to rRT-PCR (33.2% and 36.0%). rRT-PCR SARS-CoV-2 detection in self-collected GL samples had a similar PPA and NPA to that of NPSs. GL self-sampling offers a suitable and more comfortable alternative for SARS-CoV-2 detection.

Performance Analysis of Self-Collected Nasal and Oral Swabs for Detection of SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the third highly pathogenic human coronavirus and is rapidly transmitted by infected individuals regardless of their symptoms. During the COVID-19 pandemic, owing to the dearth of skilled healthcare workers (HCWs) to collect samples for early diagnosis, self-collection emerged as a viable alternative. To evaluate the reliability of self-collection, we compared the virus detection rate using 3990 self-collected swabs and HCW-collected swabs, procured from the same individuals and collected immediately after the self-collection. The results of multiplex reverse-transcription quantitative polymerase chain reaction revealed that the viral load in the HCW-collected swabs was marginally (18.4–28.8 times) higher than that in self-collected swabs. Self-collection showed no significant difference in sensitivity and specificity from HCW-collection (κ = 0.87, McNemar’s test; p = 0.19), indicating a comparable performance. These findings suggest that self-collected swabs are acceptable substitutes for HCW-collected swabs, and that their use improved the specimen screening efficiency and reduced the risk of SARS-CoV-2 infection among HCWs during and after the COVID-19 pandemic.

Clinical Performance of Self-Collected Nasal Swabs and Antigen Rapid Tests for SARS-CoV-2 Detection in Resource-Poor Settings

Background: In resource-poor countries, antigen-based rapid tests (Ag-RDTs) performed at primary healthcare and community settings improved access to SARS-CoV-2 diagnostics. However, the technical skills and biosafety requirements inherent to nasopharyngeal and oropharyngeal (OP) specimens limit the scale-up of SARS-CoV-2 testing. The collection of nasal-swabs is programmatically viable, but its performance has not been evaluated in resource-poor settings. Methods: We first evaluated the performance of SteriPack self-collected nasal swabs for the detection of SARS-CoV-2 by real-time PCR in 1498 consecutively enrolled patients with suspected infection. Next, we evaluated the clinical performance of three nasal swab-based Ag-RDTs against real-time PCR on OP specimens. Results: The sensitivity of nasal swabs was 80.6% [95% CI: 75.3−85.2%] compared to OP specimens. There was a good correlation (r = 0.58; p < 0.0001) between Ct values of 213 positive cases obtained using nasal and OP swabs. Our findings show sensitivities of 79.7% [95% CI: 73.3−85.1%] for Panbio COVID-19 Ag-RDT, 59.6% [95% CI: 55.2−63.8%] for COVIOS Ag-RDT, and 78.0% [95% CI: 73.5−82.0%] for the LumiraDx SARS-CoV-2 Ag-RDT. Conclusions: In our setting, the COVIOS Ag-RDT did not meet WHO requirements. Nasal swab-based Ag-RDTs for SARS-CoV-2 detection constitute a viable and accurate diagnostic option in resource-poor settings.

Advanced Molecular and Immunological Diagnostic Methods to Detect SARS-CoV-2 Infection

COVID-19 emerged in late 2019 in China and quickly spread across the globe, causing over 521 million cases of infection and 6.26 million deaths to date. After 2 years, numerous advances have been made. First of all, the preventive vaccine, which has been implemented in record time, is effective in more than 95% of cases. Additionally, in the diagnostic field, there are numerous molecular and antigenic diagnostic kits that are equipped with high sensitivity and specificity. Real Time-PCR-based assays for the detection of viral RNA are currently considered the gold-standard method for SARS-CoV-2 diagnosis and can be used efficiently on pooled nasopharyngeal, or oropharyngeal samples for widespread screening. Moreover, additional, and more advanced molecular methods such as droplet-digital PCR (ddPCR), clustered regularly interspaced short palindromic repeats (CRISPR) and next-generation sequencing (NGS), are currently under development to detect the SARS-CoV-2 RNA. However, as the number of subjects infected with SARS-CoV-2 continuously increases globally, health care systems are being placed under increased stress. Thus, the clinical laboratory plays an important role, helping to select especially asymptomatic individuals who are actively carrying the live replicating virus, with fast and non-invasive molecular technologies. Recent diagnostic strategies, other than molecular methods, have been adopted to either detect viral antigens, i.e., antigen-based immunoassays, or human anti-SARS-CoV-2 antibodies, i.e., antibody-based immunoassays, in nasal or oropharyngeal swabs, as well as in blood or saliva samples. However, the role of mucosal sIgAs, which are essential in the control of viruses entering the body through mucosal surfaces, remains to be elucidated, and in particular the role of the immune response in counteracting SARS-CoV-2 infection, primarily at the site(s) of virus entry that appears to be promising.

Performance of nasopharyngeal swab and saliva in detecting Delta and Omicron SARS-CoV-2 variants

A prospective cohort study was conducted during the Delta and Omicron severe acute respiratory syndrome coronavirus type 2 (SARS‐CoV‐2) epidemic waves from paired nasopharyngeal swab (NPS or NP swab) and saliva samples taken from 624 participants. The study aimed to assess if any differences among participants from both waves could be observed and if any difference in molecular diagnostic performance could be observed among the two sample types. Samples were transported immediately to the laboratory to ensure the highest possible sample quality without any freezing and thawing steps before processing. Nucleic acids from saliva and NPS were prospectively extracted and SARS‐CoV‐2 was detected using a real‐time reverse‐transcription polymerase chain reaction. All observed results were statistically analyzed. Although the results obtained with NP and saliva agreed overall, higher viral loads were observed in NP swabs regardless of the day of specimen collection in both SARS‐CoV‐2 epidemic waves. No significant difference could be observed between the two epidemic waves characterized by Delta or Omicron SARS‐CoV‐2. To note, Delta infection resulted in higher viral loads both in NP and saliva and more symptoms, including rhinorrhea, cough, and dyspnea, whereas Omicron wave patients more frequently reported sore throat. An increase in the mean log RNA of SARS‐CoV‐2 was observed with the number of expressed symptoms in both waves, however, the difference was not significant. Data confirmed that results from saliva were concordant with those from NP swabs, although saliva proved to be a challenging sample with frequent inhibitions that required substantial retesting.

Evaluation of water gargle samples for SARS-CoV-2 detection using Abbott ID NOW COVID-19 assay

The Abbott ID NOW™ COVID‐19 assay has been shown as a reliable and sensitive alternative to reverse transcription‐polymerase chain reaction (RT‐PCR) testing from nasopharyngeal or nasal samples in symptomatic patients. Water gargle is an acceptable noninvasive alternative specimen for severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2) detection by RT‐PCR. The objective of this study was to evaluate the performance of water gargle samples for the detection of SARS‐CoV‐2 using the ID NOW. Residual gargle samples were randomly selected among positive standard of care (SOC)‐nucleic acid amplification test (NAAT) samples. For testing on ID NOW, the manufacturer's instructions were followed, except for the specimen addition step: 500 µl of the gargle specimen was added to the blue sample receiver with a pipette and gently mixed. Among the 202 positive samples by SOC‐NAAT, 185 were positive by ID NOW (positive percent agreement [PPA]) = 91.6% (95% confidence interval [CI]: 86.9−95.0). For the 17 discordant samples, cycle threshold (C_t) values were all ≥31.0. The PPA was significantly lower among asymptomatic patients (84.4%; 95% CI: 73.2−92.3) versus symptomatic patients (95.2%; 95% CI: 89.8−98.2). The performance of the ID NOW for the detection of SARS‐CoV‐2 infection on gargle samples is excellent when C_t values are <31.0 and for patients that have COVID‐19 compatible symptoms.

Comparison of Allplex™ 2019-nCoV and TaqPath™ COVID-19 Assays

The clinical presentation of COVID-19 is non-specific, and to improve and limit the spread of the SARS-CoV-2 virus, an accurate diagnosis with a robust method is needed. A total of 500 nasopharyngeal swab specimens were tested for SARS-CoV-2. Of these, 184 samples were found to be positive with Allplex™ 2019-nCoV Assay, which is fully automated. All the positive samples were retested with TaqPath™ COVID-19 CE-IVD RT-PCR Kit (after this, referred to as TaqPath™ COVID-19), semi-automated. The comparison of RT-qPCR for SARS-CoV-2 genes target points shows only one target point in common, the N gene. Therefore, the N gene was used to compare both assays. We noticed different Ct values between the tests. Therefore, samples were divided into four groups depending to the Ct value results: (1) Ct < 25, (2) Ct 25–30, (3) Ct 30–35, (4) Ct > 35. TaqPath™ COVID-19 Kit reconfirmed the results obtained from Allplex™ 2019-nCoV Assay. In conclusion, both the Allplex™ 2019-nCoV assay and TaqPath™ COVID-19 tests accurately confirm the diagnosis of SARS-CoV-2 infection. Even if TaqPath™ COVID-19 has a semi-automated workflow, it does not introduce bias in the diagnostic screening of SARS-CoV-2, and it supports the indirect identification of variants of concern to undergo sequencing.

Acceptability of Community Saliva Testing in Controlling the COVID-19 Pandemic: Lessons Learned from Two Case Studies in Nursing Homes and Schools

Current public health debate centers on COVID-19 testing methods and strategies. In some communities, high transmission risk may justify routine testing, and this requires test methods that are safe and efficient for both patients and the administrative or health-care workers administering them. Saliva testing appears to satisfy those criteria. There is, however, little documentation on the acceptability of this method among beneficiaries. This article presents the lessons learned from a pilot study on the use of saliva testing for routine screening of nursing home and secondary school personnel in Wallonia (the French-speaking part of Belgium), conducted in December 2020 to April 2021, respectively. Administrators at the facilities in question seemed to think highly of saliva testing and wished to continue it after the pilot study was over. This result reinforces the criteria (the noninvasive aspect, in particular) supporting a key role for saliva testing in monitoring community spread of the virus. Nevertheless, wider-scale deployment of this particular method will only be possible if the testing strategy as a whole takes a health promotion approach.