Evaluation of extraction-free RT-qPCR methods for SARS-CoV-2 diagnostics

Evaluating an extraction-free sample preparation method for multiplex detection of SARS-Cov-2, influenza A/B, and RSV with implementation on a microfluidic chip

Following the relaxation of COVID-19 restrictions, other respiratory viruses such as influenza and respiratory syncytial virus (RSV), whose transmission were decreased due to COVID-19 precautions, are rising again. Because of similar clinical features and reported co-infections, multiplex detection of SARS-CoV-2, influenza A/B, and RSV is required to use specific treatments. This study assessed an extraction-free sample preparation (heat treatment at 95°C for 3 minutes) for multiplex detection using rRT-PCR. Despite an observed Ct-delay (∆Ct) averageing 1.26 compared to the standard method, an acceptable total sensitivity of 92 % and a negative predictive value (NPV) of 96 % were obtained. Moreover, Implementation on a microfluidic chip demonstrated efficiency, maintaining an excellent correlation (R2=0.983) with the standard method. Combining this extraction-free procedure with rRT-PCR on a microfluidic chip seems promising, because it simplifies the design and reduces the cost and complexity of the integrated assay for multiplex detection of SARS-CoV-2, influenza A/B, and RSV.

Comparative Bioinformatic Analysis Reveals Conserved Regions in SARS-CoV-2 Genome for RAPID Pandemic Response

In the face of the SARS-CoV-2 pandemic, characterized by the virus's rapid mutation rates, developing timely and targeted therapeutic and diagnostic interventions presents a significant challenge. This study utilizes bioinformatic analyses to pinpoint conserved genomic regions within SARS-CoV-2, offering a strategic advantage in the fight against this and future pathogens. Our approach has enabled the creation of a diagnostic assay that is not only rapid, reliable, and cost-effective but also possesses a remarkable capacity to detect a wide array of current and prospective variants with unmatched precision. The significance of our findings lies in the demonstration that focusing on these conserved genomic sequences can significantly enhance our preparedness for and response to emerging infectious diseases. By providing a blueprint for the development of versatile diagnostic tools and therapeutics, this research paves the way for a more effective global pandemic response strategy.

Overview of the different methods for RNA preparation in COVID-19 diagnosis process during the pandemic

The COVID-19 pandemic brought to light the impact of a widespread disease on various aspects of human relationships, communities, and economies. One notable consequence was the increased demand for diagnostic kits, laboratory reagents, and personal health equipment. This surge in testing capacity worldwide led to shortages in the supply of essential items, including RNA extraction kits, which are crucial for detecting COVID-19 infections. To address this scarcity, researchers have proposed alternative and cost-effective strategies for RNA extraction, utilizing both chemical and physical solutions and extraction-free methods. These approaches aim to alleviate the challenges associated with the overwhelming number of tests being conducted in laboratories. The purpose of this review is intends to provide a comprehensive summary of the various kit-free RNA extraction methods available for COVID-19 diagnosis during the pandemic.

Development and application of a universal extraction-free reagent based on an algal glycolipid

In this study, we independently developed a universal nasopharyngeal swab extraction-free reagent based on a trehalose lipid for the rapid detection of pathogen nucleic acids in respiratory infectious diseases. By comparing the isothermal amplification results of a 2019-nCoV pseudovirus solution treated with different components of the extraction-free reagent, we determined the optimal composition of the extraction-free reagent to be a mixed solution of 10 mmol L-1 tris-HCl containing 0.05 mmol L-1 EDTA (TE solution), 5% glycine betaine, 0.5% Triton X-100, and 1.5% trehalose lipid. The results showed that the extraction-free reagent could cleave DNA viruses, RNA viruses, and bacteria to release nucleic acids and did not affect the subsequent nucleic acid amplification. Its efficiency was consistent with that of magnetic bead extraction. Real-time fluorescence quantitative PCR was used to analyze the stability and repeatability of the detection results of the samples treated with the extraction-free reagent and the sensitivity of the extraction-free reagent. The results showed that the extraction-free kit could stably store the pathogen nucleic acid for at least 24 hours, the detection repeatability was satisfactory, and there was no incompatibility with the detection limits of various manufacturers' nucleic acid detection reagents. In conclusion, the established nucleic acid extraction-free method can effectively lyse respiratory infectious disease pathogens to release nucleic acids (DNA and RNA) at room temperature and can directly amplify nucleic acids without extraction steps. This method takes a short time and has high efficiency. The released nucleic acid met the requirements of molecular biological detection methods such as real-time fluorescence quantitative PCR (qPCR), reverse transcription-polymerase chain reaction (RT-PCR), and isothermal nucleic acid amplification (INAA).

Real-world performance of SARS-CoV-2 rapid antigen testing through the Alpha-, Delta- and Omicron-dominant waves of the COVID-19 pandemic

OBJECTIVES

Compared with reverse transcription polymerase chain reaction (RT-PCR), rapid antigen detection tests (RADTs) for SARS-CoV-2 diagnostics are faster, less expensive, but also less accurate. Performance of RADTs is context-specific and depends on disease prevalence. In this real-world study, we assessed impact of RADTs in an inpatient setting through the entire COVID-19 emergency phase.

METHODS

In this matched retrospective study, data on RT-PCR and RADT laboratory diagnoses of SARS-CoV-2 made between February 2020 and May 2023 in a large hospital were analyzed. To be included in the study, samples used for both RT-PCR and RADT had to be collected on the same day.

RESULTS

Of 278,867 RT-PCR tests available, 13,321 same-day RADTs could be matched to RT-PCR. Over the entire period, RADT sensitivity and specificity were 76.4% and 99.4%, respectively. With the observed positivity rate of 9.4%, positive and negative predictive values were 92.7% and 97.6%, respectively. Compared with the periods dominated by the Alpha and Delta variants of concern, RADT accuracy was slightly lower during the Omicron phase.

CONCLUSION

This real-world experience demonstrates that despite suboptimal sensitivity and some variation by predominant variants of concern and positivity prevalence, the use of RADTs is useful in hospital settings. Public health implications were discussed.

The Diagnostic Performance of Various Clinical Specimens for the Detection of COVID-19: A Meta-Analysis of RT-PCR Studies

BACKGROUND

The diagnostic performance of numerous clinical specimens to diagnose COVID-19 through RT-PCR techniques is very important, and the test result outcome is still unclear. This review aimed to analyze the diagnostic performance of clinical samples for COVID-19 detection by RT-PCR through a systematic literature review process.

METHODOLOGY

A compressive literature search was performed in PubMed/Medline, Scopus, Embase, and Cochrane Library from inception to November 2022. A snowball search on Google, Google Scholar, Research Gate, and MedRxiv, as well as bibliographic research, was performed to identify any other relevant articles. Observational studies that assessed the clinical usefulness of the RT-PCR technique in different human samples for the detection or screening of COVID-19 among patients or patient samples were considered for this review. The primary outcomes considered were sensitivity and specificity, while parameters such as positive predictive value (PPV), negative predictive value (NPV), and kappa coefficient were considered secondary outcomes.

RESULTS

A total of 85 studies out of 10,213 non-duplicate records were included for the systematic review, of which 69 articles were considered for the meta-analysis. The meta-analysis indicated better pooled sensitivity with the nasopharyngeal swab (NPS) than saliva (91.06% vs. 76.70%) and was comparable with the combined NPS/oropharyngeal swab (OPS; 92%). Nevertheless, specificity was observed to be better with saliva (98.27%) than the combined NPS/OPS (98.08%) and NPS (95.57%). The other parameters were comparable among different samples. The respiratory samples and throat samples showed a promising result relative to other specimens. The sensitivity and specificity of samples such as nasopharyngeal swabs, saliva, combined nasopharyngeal/oropharyngeal, respiratory, sputum, broncho aspirate, throat swab, gargle, serum, and the mixed sample were found to be 91.06%, 76.70%, 92.00%, 99.44%, 86%, 96%, 94.4%, 95.3%, 73.63%, and above 98; and 95.57%, 98.27%, 98.08%, 100%, 37%, 100%, 100%, 97.6%, and above 97, respectively.

CONCLUSIONS

NPS was observed to have relatively better sensitivity, but not specificity when compared with other clinical specimens. Head-to-head comparisons between the different samples and the time of sample collection are warranted to strengthen this evidence.

Long follow-up of BNT162b2 mRNA vaccine in healthcare workers (2020-2022): A retrospective longitudinal SARS-CoV-2 serological surveillance

SARS-CoV-2 anti-spike IgG production and protection from severe respiratory illness should be explored in greater depth after COVID-19 booster vaccination. This longitudinal observational retrospective study investigated the anti-spike IgG response elicited by the first, second and booster doses of BNT162b2 mRNA vaccine in healthcare workers (HCW) at San Martino IRCCS Policlinico Hospital (Genoa) up to the 12th month. Sequential blood sampling was performed at T0 (prior to vaccination), T1 (21 days after the 1st dose of vaccine), T2, T3, T4, T5, T6 (7 days and 1, 3, 6 and 9 months after the 2nd dose, respectively), T7 and T8 (1 and 3 months after a booster dose). A SARS-CoV-2 IgG panel (Bio-Rad, Marnes-la-Coquette, France) was used to determine levels of receptor-binding domain (RBD), spike-1 (S1), spike-2 and nucleocapsid structural proteins of SARS-CoV-2. In the 51 HCWs evaluated, seroprevalence was 96% (49/51) at T1 and 100% (51/51) from T2 to T5 for RBD and S1. At T6, only one HCW was negative. T2 [RBD = 2945 (IQR:1693-5364); S1 = 1574 (IQR:833-3256) U/mL], and T7 [RBD = 8204 (IQR:4129-11,912); S1 = 4124 (IQR:2124-6326) U/mL] were characterized by the highest antibody values. Significant humoral increases in RBD and S1 were documented at T7 and T8 compared to T2 and T4, respectively (p-value < .001). Following vaccination with BNT162b2 and a booster dose in the 9th month, naïve and healthy subjects show high antibody titers up to 12 months and a protective humoral response against COVID-19 disease lasting up to 20 months after the last booster.

Performance of the VitaPCR rapid molecular test for SARS-CoV-2 screening at hospital admission

OBJECTIVE

To evaluate the diagnostic accuracy of rapid VitaPCR™ (Credo) assay as screening test in emergency department (ED) patients prior to transfer or medical interventions.

METHODS

In this prospective study 6642 oropharyngeal swabs from nonpreselected ED patients were tested for SARS-CoV-2 with (1) extraction-free VitaPCR and (2) extraction-based reference assays (Aptima®, cobas®, Xpert®Xpress).

RESULTS

The median TAT of VitaPCR was 47 minutes (IQR: 38-59), while reference assays required 6.2 hours (IQR: 4.4-13.3). VitaPCR's sensitivity, specificity, PPV and NPV was 77.9%, 99.9%, 97.9%, and 98.9% in relation to Hologic Panther TMA; 78.3%, 99.8%, 96.4%, and 98.5% compared to Roche cobas6800 PCR; 71.2%, 99.2%, 94.9%, and 94.3% using Cepheid GeneXpert PCR as reference.

CONCLUSION

High-sensitivity testing is needed to limit nosocomial spread and identify asymptomatic COVID-19 patients. However, time advantage of the VitaPCR must be weighed against its significantly lower sensitivity, especially when used in high-risk environments such as hospitals.

SARS-CoV2 in public spaces in West London, UK during COVID-19 pandemic

BACKGROUND

Spread of SARS-CoV2 by aerosol is considered an important mode of transmission over distances >2 m, particularly indoors.

OBJECTIVES

We determined whether SARS-CoV2 could be detected in the air of enclosed/semi-enclosed public spaces.

METHODS AND ANALYSIS

Between March 2021 and December 2021 during the easing of COVID-19 pandemic restrictions after a period of lockdown, we used total suspended and size-segregated particulate matter (PM) samplers for the detection of SARS-CoV2 in hospitals wards and waiting areas, on public transport, in a university campus and in a primary school in West London.

RESULTS

We collected 207 samples, of which 20 (9.7%) were positive for SARS-CoV2 using quantitative PCR. Positive samples were collected from hospital patient waiting areas, from hospital wards treating patients with COVID-19 using stationary samplers and from train carriages in London underground using personal samplers. Mean virus concentrations varied between 429 500 copies/m³ in the hospital emergency waiting area and the more frequent 164 000 copies/m³ found in other areas. There were more frequent positive samples from PM samplers in the PM2.5 fractions compared with PM10 and PM1. Culture on Vero cells of all collected samples gave negative results.

CONCLUSION

During a period of partial opening during the COVID-19 pandemic in London, we detected SARS-CoV2 RNA in the air of hospital waiting areas and wards and of London Underground train carriage. More research is needed to determine the transmission potential of SARS-CoV2 detected in the air.

Evaluation of STANDARDTM M10 SARS-CoV-2 assay as a diagnostic tool for SARS-CoV-2 in nasopharyngeal or oropharyngeal swab samples

The SARS-CoV-2 pandemic led to an urgent need for rapid diagnostic testing in order to inform timely patients' management. This study aimed to assess the performance of the STANDARD™ M10 SARS-CoV-2 assay as a diagnostic tool for COVID-19. A total of 400 nasopharyngeal or oropharyngeal swabs were tested against a reference real-time RT-PCR, including 200 positive samples spanning the full range of observed Ct values. The sensitivity of the STANDARD™ M10 SARS-CoV-2 assay was 98.00% (95% CI 94.96% to 99.45%, 196/200), while the specificity was also estimated at 97.50% (95% CI 94.26% to 99.18%, 195/200). The assay proved highly efficient for the detection of SARS-CoV-2, even in samples with low viral load (Ct>25), presenting lower Ct values compared to the reference method. We concluded that the STANDARD™ M10 SARS-CoV-2 assay has a similar performance compared to the reference method and other molecular point-of-care assays and can be a valuable tool for rapid and accurate diagnosis.

High Diagnostic Accuracy of a Novel Lateral Flow Assay for the Point-of-Care Detection of SARS-CoV-2

Highly accurate lateral flow immunochromatographic tests (LFTs) are an important public health tool to tackle the ongoing COVID-19 pandemic. The aim of this study was to assess the comparative diagnostic performance of the novel ND COVID-19 LFT under real-world conditions. A total of 400 nasopharyngeal swab specimens with a wide range of viral loads were tested in both reverse-transcription polymerase chain reaction and ND LFT. The overall sensitivity and specificity were 85% (95% CI: 76.7−90.7%) and 100% (95% CI: 98.7−100%), respectively. There was a clear association between the false-negative rate and sample viral load: the sensitivity parameters for specimens with cycle threshold values of <25 (>3.95 × 106 copies/mL) and ≥30 (≤1.29 × 105 copies/mL) were 100% and 50%, respectively. The performance was maximized in testing samples with viral loads ≥1.29 × 105 copies/mL. These findings suggest that the ND LFT is sufficiently accurate and useful for mass population screening programs, especially in high-prevalence and resource-constrained settings or during periods when the epidemic curve is rising. Other public health implications were also discussed.

Efficacy of the Sentinox Spray in Reducing Viral Load in Mild COVID-19 and Its Virucidal Activity against Other Respiratory Viruses: Results of a Randomized Controlled Trial and an In Vitro Study

Sentinox (STX) is an acid-oxidizing solution containing hypochlorous acid in spray whose virucidal activity against SARS-CoV-2 has been demonstrated. In this paper, results of a randomized controlled trial (RCT) on the efficacy of STX in reducing viral load in mild COVID-19 patients (NCT04909996) and a complementary in vitro study on its activity against different respiratory viruses are reported. In the RCT, 57 patients were randomized (1:1:1) to receive STX three (STX-3) or five (STX-5) times/day plus standard therapy or standard therapy only (controls). Compared with controls, the log10 load reduction in groups STX-3 and STX-5 was 1.02 (p = 0.14) and 0.18 (p = 0.80), respectively. These results were likely driven by outliers with extreme baseline viral loads. When considering subjects with baseline cycle threshold values of 20-30, STX-3 showed a significant (p = 0.016) 2.01 log10 reduction. The proportion of subjects that turned negative by the end of treatment (day 5) was significantly higher in the STX-3 group than in controls, suggesting a shorter virus clearance time. STX was safe and well-tolerated. In the in vitro study, ≥99.9% reduction in titers against common respiratory viruses was observed. STX is a safe device with large virucidal spectrum and may reduce viral loads in mild COVID-19 patients.

Clinical Evaluation of Nasopharyngeal, Oropharyngeal, Nasal Swabs, and Saliva for the Detection of SARS-CoV-2 by Direct RT-PCR

Nasopharyngeal swab (NPS) and oropharyngeal swab (OPS) are the most widely used upper respiratory tract specimens for diagnosis of SARS-CoV-2 using RT-qPCR. In contrast, nasal swab (NS) and saliva (SS), recently recommended by the WHO, are rarely used, and their test accuracy is limited. The method for direct RT-PCR detection of SARS-CoV-2 does not require an RNA extraction and is faster and easier than standard RT-PCR tests with RNA extraction. This study aimed to compare the diagnostic performance of upper respiratory tract samples for SARS-CoV-2 detection using the direct RT-PCR without preliminary heat inactivation. Here we report the application and validation of direct RT-PCR SARS-CoV-2 RNA on 165 clinical specimens of NPS/OP, and 36 samples of NS/NPS and 37 saliva samples (for the latter with prior deproteinization). The overall sensitivity estimates were 95.9%, 94.2%, 88.9%, and 94.6% for NPS/OPS/NS/SS samples, respectively, and the specificity was 100% against standard RT-PCR with RNA extraction. Overall, NS and SS testing by direct RT-PCR had sufficient sensitivity to detect SARS-CoV-2. They can be acceptable alternative to NPS/OPS for rapid detection of SARS-CoV-2 infections in future.

Comparative Diagnostic Accuracy of the STANDARD M10 Assay for the Molecular Diagnosis of SARS-CoV-2 in the Point-of-Care and Critical Care Settings

Accurate and rapid molecular diagnosis of COVID-19 is a crucial step to tackle the ongoing pandemic. The primary objective of this study was to estimate the real-world performance of the novel RT-PCR STANDARD M10 SARS-CoV-2 assay in a large number of nasopharyngeal (NP) specimens eluted in universal transport medium. The secondary objective was to evaluate the compatibility of this kit in testing NP samples eluted in an inactivated transport medium (essential for point-of-care testing) and lower respiratory tract (LRT) specimens, which are commonly collected in critical care. A total of 591 samples were analyzed. Compared with the standard extraction-based RT-PCR Allplex 2019-nCoV (time-to-result of 270 min), the sensitivities of the STANDARD M10 were 100% (95% CI: 98.1-100%), 95.5% (95% CI: 91.7-97.6%), and 99.5% (95% CI: 97.2-99.9%) for ≥1 gene, the ORF1ab gene, and the E gene, respectively, while the specificity was 100% (95% CI: 98.7-100%). The diagnostic accuracy was 100% in testing both NP samples eluted in an inactivated transport medium and LRT specimens. STANDARD M10 reliably detects SARS-CoV-2 in 60 min, may be used as a POC tool, and is suitable for testing LRT specimens in the critical care setting.

Effect of the 2020/21 season influenza vaccine on SARS-CoV-2 infection in a cohort of Italian healthcare workers

OBJECTIVES

Healthcare workers (HCWs) are a priority group for seasonal influenza vaccination (SIV). The 2020/21 SIV campaign was conducted during the second wave of the COVID-19 pandemic. Vaccines, including SIV, may exert non-specific protective effects on other infectious diseases which may be ascribable to the concept of trained immunity. The aim of this study was to explore the association between 2020/21 SIV and SARS-CoV-2 positivity in a cohort of Italian HCWs.

METHODS

In this observational study, a cohort of HCWs employed by a large (ca 5000 employees) referral tertiary acute-care university hospital was followed up retrospectively until the start of the COVID-19 vaccination campaign. The independent variable of interest was the 2020/21 SIV uptake. Both egg-based and cell culture-derived quadrivalent SIVs were available. The study outcome was the incidence of new SARS-CoV-2 infections, as determined by RT-PCR. Multivariable Cox regression was applied in order to discern the association of interest.

RESULTS

The final cohort consisted of 2561 HCWs who underwent ≥1 RT-PCR test and accounted for a total of 94,445 person-days of observation. SIV uptake was 35.6%. During the study period, a total of 290 new SARS-CoV-2 infections occurred. The incidence of new SARS-CoV-2 was 1.62 (95% CI: 1.22-2.10) and 3.91 (95% CI: 3.43-4.45) per 1000 person-days in vaccinated and non-vaccinated HCWs, respectively, with an adjusted non-proportional hazard ratio of 0.37 (95% CI: 0.22-0.62). E-values suggested that unmeasured confounding was unlikely to explain the association.

CONCLUSIONS

A lower risk of SARS-CoV-2 infection was observed among SIV recipients.

Comparative Analysis of Five Multiplex RT-PCR Assays in the Screening of SARS-CoV-2 Variants

The rapid and presumptive detection of SARS-CoV-2 variants may be performed using multiplex RT-PCR assays. The aim of this study was to evaluate the diagnostic performance of five qualitative RT-PCR tests as compared with next-generation sequencing (NGS). We retrospectively examined a multi-variant panel (n = 72) of SARS-CoV-2-positive nasopharyngeal swabs categorized as variants of concern (Alpha, Beta, Gamma and Delta), variants under monitoring (Iota and Kappa) and wild-type strains circulating in Liguria (Italy) from January to August 2021. First, NGS libraries of study samples were prepared and mapped to the reference genome. Then, specimens were screened for the detection of L452R, W152C, K417T, K417N, E484Q, E484K and N501Y mutations using the SARS-CoV-2 Variants II Assay Allplex, UltraGene Assay SARS-CoV-2 452R & 484K & 484Q Mutations V1, COVID-19 Ultra Variant Catcher, SARS-CoV-2 Extended ELITe MGB and Simplexa SARS-CoV-2 Variants Direct. The overall accuracy of these assays ranged from 96.9% to 100%. Specificity and sensitivity were 100% and 96-100%, respectively. We highly recommend the use of these assays as second-level tests in the routine workflow of SARS-CoV-2 laboratory diagnostics, as they are accurate, user friendly, low cost, may identify specific mutations in about 2-3 h and, therefore, optimize the surveillance of SARS-CoV-2 variants.

Comparative Diagnostic Performance of a Novel Reverse Transcription Loop-Mediated Isothermal Amplification (RT-LAMP) Kit for the Rapid Detection of SARS-CoV-2

Although the reverse transcription-polymerase chain reaction (RT-PCR) is considered a standard-of-care assay for the laboratory diagnosis of SARS-CoV-2, several limitations of this method have been described. Reverse transcription loop-mediated isothermal amplification (RT-LAMP) is an alternative molecular assay and is potentially able to overcome some intrinsic shortcomings of RT-PCR. In this study, we evaluated the diagnostic performance of the novel HG COVID-19 RT-LAMP assay. In this retrospective analysis, a total of 400 routinely collected leftover nasopharyngeal samples with a known RT-PCR result were tested by means of the HG COVID-19 RT-LAMP assay. The overall sensitivity and specificity values of HG COVID-19 RT-LAMP versus RT-PCR were 97.0% (95% CI: 93.6-98.9%) and 98.5% (95% CI: 95.7-99.7%), respectively. Inter-assay agreement was almost perfect (κ = 0.96). Concordance was perfect in samples with high viral loads (cycle threshold < 30). The average time to a positive result on RT-LAMP was 17 min. HG COVID-19 RT-LAMP is a reliable molecular diagnostic kit for detecting SARS-CoV-2, and its performance is comparable to that of RT-PCR. Shorter turnaround times and the possibility of performing molecular diagnostics in the point-of-care setting make it a valuable option for facilities without sophisticated laboratory equipment.

Point-of-Care Diagnostic Tools for Surveillance of SARS-CoV-2 Infections

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a recently emerged and highly contagious virus that causes coronavirus disease 2019 (COVID-19). As of August 24, 2021, there were more than 212 million confirmed COVID-19 cases and nearly 4.4 million deaths reported globally. Early diagnosis and isolation of infected individuals remains one of the most effective public health interventions to control SARS-CoV-2 spread and for effective clinical management of COVID-19 cases. Currently, SARS-CoV-2 infection is diagnosed presumptively based on clinical symptoms and confirmed by detecting the viral RNA in respiratory samples using reverse transcription polymerase chain reaction (RT-PCR). Standard RT-PCR protocols are time consuming, expensive, and technically demanding, which makes them a poor choice for large scale and point-of-care screening in resource-poor settings. Recently developed isothermal nucleic acid amplification tests (iNAAT), antigen and/or serological tests are cost-effective to scale COVID-19 testing at the point-of-care (PoC) and for surveillance activities. This review discusses the development of rapid PoC molecular tools for the detection and surveillance of SARS-CoV-2 infections.