Cycle Threshold Research Articles

Molecular Detection of Anaplasma marginale in Capybara (Hydrochoerus hydrochaeris) from Corrientes, Argentina.

Monitoring wildlife health is essential for understanding global disease patterns, particularly as vector-borne infections extend the geographic ranges and thereby hosts due to environmental shifts. Anaplasma marginale, primarily impacting cattle, has economic implications and has been found in diverse hosts, yet its presence in capybaras (Hydrochoerus hydrochaeris), influential in tick-borne pathogen spread, lacks comprehensive understanding. From 2015 to 2022, 14 capybaras were surveyed across two different areas of northeastern Argentina. In 1 of 14 (7%) capybaras, the presence of A. marginale was confirmed through the amplification of specific genes, msp5 and msp1β. In addition, A. marginale DNA was detected in the capybara's blood sample through quantitative PCR, with a cycle threshold value of 30.81 (800 copies per reaction). Amplification of a fragment of the msp1α gene revealed PCR products of three different sizes, suggesting the presence of at least three coinfecting A. marginale variants in the capybara host. This study suggests that capybaras are wild hosts for A. marginale in the Ibera Wetlands in Argentina, potentially influencing the infection dynamics of both domestic and wild species. This finding highlights the necessity for thorough studies on the role of capybaras in disease dynamics, crucial for understanding wildlife health and the spread of disease.

Cycle Threshold Values of SARS-CoV-2 RT-PCR during Outbreaks in Nursing Homes: A Retrospective Cohort Study.

a retrospective cohort design with Poisson regression and multinomial logistic regression were used. We studied four nursing home SARS-CoV-2 outbreaks, and the average infection rate, reinfection rate, and case fatality were 72.7%, 19.9%, and 5.5%, respectively; 98.9% of residents were vaccinated with three doses of a mRNA SARS-CoV-2 vaccine. Ct values for first infections and reinfections were 27.1 ± 6.6 and 31.9 ± 5.4 (p = 0.000). Considering Ct values ≥ 30 versus <30, residents with reinfections had Ct values higher than residents with a first infection, an adjusted relative risk of 1.66 (95% Confidence interval 1.10-2.51). A sensitivity analysis confirmed these results. Reinfection and SARS-CoV-2 vaccination (hybrid immunity) could protect against severe disease better than vaccination alone. High Ct values suggest lower transmission and severity. Its value can be useful for surveillance and forecasting future SARS-CoV-2 epidemics.

Evaluation of the Seegene Allplex™ RV master assay for one-step simultaneous detection of eight respiratory viruses in nasopharyngeal specimens

BackgroundThe Seegene Allplex™ RV Master (RVM) assay is a one-step multiplex real-time reverse transcription polymerase chain reaction (RT-PCR) system for detecting eight viral respiratory pathogens from nasopharyngeal swab, aspirate, and bronchoalveolar lavage specimens. The eight RVM targets are: severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), Influenza A (Flu A), Influenza B (Flu B), Human respiratory syncytial virus (RSV), adenovirus (AdV), rhinovirus (HRV), parainfluenza virus (PIV), and metapneumovirus (MPV). The assay is based on Seegene’s multiple detection temperature (MuDT) technology and provides cycle threshold (Ct) values for each of its viral targets upon PCR completion. ObjectiveWe aimed to evaluate the diagnostic performance of the RVM assay by calculating sensitivity, specificity, accuracy, Positive Predictive Value (PPV), Negative Predictive Value (NPV), Positive Percent Agreement (PPA), Negative Percent Agreement (NPA), and Overall Percent Agreement (OPA) compared to definite diagnosis and analogous reference assays. Study designDiagnostic sensitivity, specificity, accuracy, PPV, and NPV were calculated by comparing the results of the RVM assay to that of definite diagnosis assays; while PPA, NPA, and OPA were calculated by comparing results of the RVM assay to that of analogous reference products. Definite diagnosis and reference methods comprised whole genome sequencing and PCR genotyping, the Allplex™ SARS-CoV-2/FluA/FluB/RSV and Respiratory Panels 1, 2, and 3 assays (Seegene), and the Xpert® Xpress SARS-CoV-2/FluA/FluB/RSV Plus assay (Cepheid). Reproducibility of the RVM assay using fully-automated and semi-automated nucleic acid (NA) extraction workflows and as performed by independent operators was also assessed. In total, 249 positive respiratory specimens and at least 50 negative specimens for each target tested were used for this evaluation study. ResultsSensitivity, specificity, accuracy, PPV, NPV, PPA, NPA, and OPA ranged from 95.7 % to 100 % for detecting all eight targets tested on the RVM assay. Reproducibility PPA, NPA, and OPA between automated and semi-automated NA extraction workflows were all >97.9 %, while the reproducibility PPA, NPA and OPA between independent operators were all 100 %. ConclusionThese results demonstrate a high level of sensitivity, specificity, accuracy and diagnostic predictive value of the RVM assay and high agreement with comparable reference assays in identifying all eight of its targets. Taken together, our study underscores the diagnostic utility of the RVM assay in detecting eight viral respiratory pathogens.

Correlation of COVID-19 vaccination and RT-PCR ct value among cases in Addis Ababa, Ethiopia: implication for future preparedness

BackgroundThe COVID-19 disease requires accurate diagnosis to effectively manage infection rates and disease progression. The study aims to assess the relationship between vaccination status and RT-PCR cycle threshold (Ct) values by comparing clinical, RDT and RT-PCR results.MethodsA total of 453 suspected COVID-19 cases were included in this study. Nasopharyngeal swabs were collected for both RDT and RT-PCR testing, with RDTs conducted on-site and RT-PCR at the Ethiopian Public Health Institute (EPHI) genomics laboratory. Detailed clinical, RDT, and RT-PCR results were analyzed. Data analysis included descriptive statistics, cross-tabulation, and Chi-Square tests to investigate the connections between diagnostic outcomes and vaccination status, with a focusing on Ct values.ResultsRDT results showed 34.0% negative and 65.8% positive, while RT-PCR results indicated 35.8% negative and 64.2% positive cases. The discrepancies between RDT and RT-PCR results emphasize the importance of thorough testing. No significant association was found between vaccination status and viral load, as indicated by Ct values. Among RT-PCR positive cases, 49.8% had been vaccinated, suggesting challenges in interpreting results among vaccinated individuals. Further analysis revealed that vaccination (first or second dose) had minimal impact on Ct values, indicating limited influence of vaccination status on viral load dynamics in infected individuals.ConclusionsThe study highlights the significant differences between RDT and RT-PCR outcomes, underscoring the need for a comprehensive testing approach. Additionally, the findings suggest that vaccination status does not significantly impact RT-PCR Ct values, complicating the interpretation of diagnostic results in vaccinated individuals, especially in breakthrough infections and potential false positives.

Assessing infectiousness and the impact of effective treatment to guide isolation recommendations for people with pulmonary tuberculosis.

Determining the extent and duration of infectiousness of individuals with pulmonary tuberculosis (TB) is critical for various aspects of TB care, including decisions regarding isolation. Studies suggest considerable heterogeneity in infectiousness of people with pulmonary TB. Pre-treatment, measures of bacillary burden including sputum smear microscopy, culture time-to-positivity, and Xpert MTB/RIF cycle threshold (Ct) value, predict the risk of transmission to contacts. Index patients with smear negative disease pose lower infectious risk than those who have smear-positive disease, and household contact infection is more likely with index patients who have lower Xpert Ct values. Newer tools that enable detection of Mycobacterium tuberculosis complex (Mtb complex) from cough aerosol sampling and face mask sampling may be better predictors of contact infection risk. Clinical factors such as cough strength and frequency, and presence of cavitation on chest imaging, may also assist with risk prediction. Post-treatment, smear and culture status are poor predictors of infectiousness. While the exact duration of infectiousness post treatment initiation remains uncertain, data from human-to-guinea pig transmission studies and clinical studies suggest effective treatment results in a rapid decline in infectiousness, irrespective of smear or culture conversion. This is largely supported by early bactericidal activity and transcriptomic studies, and cough aerosol sampling studies, although a subset of patients may have persistent cough aerosol positivity. These findings can enable a more nuanced approach to isolation decision making, while further research studies are awaited.

Reverse-engineered models reveal differential membrane properties of autonomic and cutaneous unmyelinated fibers.

Unmyelinated C-fibers constitute the vast majority of axons in peripheral nerves and play key roles in homeostasis and signaling pain. However, little is known about their ion channel expression, which controls their firing properties. Also, because of their small diameters (~ 1 μm), it has not been possible to characterize their membrane properties using voltage clamp. We developed a novel library of isoform-specific ion channel models to serve as the basis functions of our C-fiber models. We then developed a particle swarm optimization (PSO) framework that used the isoform-specific ion channel models to reverse engineer C-fiber membrane properties from measured autonomic and cutaneous C-fiber conduction responses. Our C-fiber models reproduced experimental conduction velocity, chronaxie, action potential duration, intracellular threshold, and paired pulse recovery cycle. The models also matched experimental activity-dependent slowing, a property not included in model optimization. We found that simple conduction responses, characterizing the action potential, were controlled by similar membrane properties in both the autonomic and cutaneous C-fiber models, but complicated conduction response, characterizing the afterpotenials, were controlled by differential membrane properties. The unmyelinated C-fiber models constitute important tools to study autonomic signaling, assess the mechanisms of pain, and design bioelectronic devices. Additionally, the novel reverse engineering approach can be applied to generate models of other neurons where voltage clamp data are not available.

B-225 Bridging the Gap Between Clinical Microbiology and Molecular Diagnostics: Correlation of PCR Cycle Threshold Values for Establishing Semi-Quantitative CFU/mL Ranges of Bacterial Targets

Abstract Background Molecular diagnostics (MolDx) has surpassed culture in the clinical microbiology laboratory. Wong (2023) states PCR is more sensitive than urine culture in detecting polymicrobial infections (para. 8), marking an advantage in MolDX for urinary tract infections. This advancement poses a challenge for clinicians in treatment decision-making. To address requests for numerical MolDx result ranges, a validation accessed semi-quantitative Colony Forming Units per milliliter (CFU/mL) through the assessment of PCR cycle threshold (CT) values. Methods Bacterial targets of UTI and STI PCR panels were inoculated in nutrient broth (Hardy diagnostics cat#K43) and incubated overnight in a shaking incubator at 35±2°C. The density of the cultures was measured using the OD600 function of a NanoDrop One/One after 18-24 hour incubation. The density of stock cultures was adjusted to 106 CFU/mL. Serial dilutions of stock were made in 1:10 steps covering the range of 106 to 100 CFU/mL. The stock and dilutions were extracted, and PCR was performed in a minimum of 2 replicates of each sample for the UTI and STI PCR panels. Mean CT values, standard deviations and coefficients of variation were calculated for each sample. The linearity of CT values within each organism’s stock and dilution samples were assessed by evaluating the CT differences between each dilution step. Corresponding CFU/mL concentrations were tabulated against each mean CT value. Results The average CT values for reportable CFU/mL ranges were established for each stock and dilution. Mean CT values for each CFU/mL breakdown across all organisms were also calculated, along with standard deviations, to investigate universal CT-CFU/mL correlations. A final interpretation table (Table 1) was constructed according to the universal range calculations. Conclusions The study confirmed correlation between CT values and CFU/mL ranges. Further data analysis and comparison with other laboratories’ results will enhance accuracy and precision of reportable CFU/mL ranges.

B-202 Clinical and analytical performance evaluation of Savanna RVP4 panel versus three methodologies

Abstract Background Rapid molecular diagnosis became a key solution for healthcare institutions across the world, after COVID-19 pandemic. It has enabled diagnosis based on improved quality, accuracy, analytical sensitivity, and turnaround times for laboratory services. It also has positioned this methodology as a trusted technology for point-of-care settings. These solutions also allow to consolidate combinations of different pathogen detection in panels. This study assessed the analytical and clinical performance of the novel Savanna RVP4 panel against other available methodologies. Methods A prospective study was performed, considering 84 patient samples obtained from nasopharyngeal swabs. Samples were processed in parallel after collection, using Savanna RVP4, and either QIAstat-Dx Respiratory SARS-CoV Panel (59 samples), Sansure iPonatic (10 samples) and BioFire® Respiratory 2.1 (RP2.1) Panel (15 samples). Samples were collected in either MTU, commercial or homemade PBS. Results Overall clinical sensitivity and specificity were 96.43% and 99.64%, respectively for the aggregated panels (Table 1). By technology, the overall clinical sensitivity and specificity were 93.75% and 99.51% versus QIAstat, 100% and 100% versus Biofire, respectively. For iPonatic comparisons, no positive samples were processed and 100% of specificity was obtained. Cycle threshold (Ct) values for positive samples were compared using box plots. Ct values also showed slighlty differences, where means were lower for RSV and Flu A in Savanna (22 and 22.9 respectively) versus other PCR assays (22.5 and 24.5 respectively). For SARS-CoV-2, Ct values were higher versus other methods (19.8 vs 13.6). Conclusions Results obtained with Savanna RVP4 were comparable to those obtained with other methodologies, correlating with patient clinical symptoms. Samples showing disagreement for QIAstat comparison panel, in Flu A and RSV assays, corresponded to the same patient samples for the two methodologies, where Ct obtained in QIAstat were above 33. This evaluation also provides strong evidence supporting PBS usage for samples processed in Savanna RVP.

Diagnostic Utility of SARS-CoV-2 Nucleocapsid Antigenemia: A Meta-analysis.

Studies of the diagnostic performance of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid antigen in blood (antigenemia) have reached variable conclusions. The potential utility of antigenemia measurements as a clinical diagnostic test needs clarification. We performed a systematic review of Pubmed, Embase, and Scopus through July 15, 2023, and requested source data from corresponding authors. Summary sensitivity from 16 studies (4543 cases) sampled at ≤14 days of symptoms was 0.83 (0.75-0.89), and specificity was 0.98 (0.87-1.00) from 6 studies (792 reverse transcription polymerase chain reaction-negative controls). Summary sensitivity and specificity for paired respiratory specimens with cycle threshold values ≤33 were 0.91 (0.85-0.95) and 0.56 (0.39-0.73) from 10 studies (612 individuals). Source data from 1779 cases reveal that >70% have antigenemia 2 weeks following symptom onset, which persists in <10% at 28 days. The available studies suffer from heterogeneity, and Omicron-era data are scarce. Nucleocapsid antigenemia currently has limited utility due to limitations of existing studies and lack of Omicron-era data. Improved study designs targeting potential clinical uses in screening, surveillance, and complex clinical decision-making-especially in immunocompromised patients-are needed.

B-229 Extraction-free Nucleic Acid Sample Preparation from Inhibitor Rich Samples via Hyperbaric Heating

Abstract Background Extraction-based nucleic acid sample preparation for PCR is limited by long processing times, liquid transfers, cost, and storage requirements. Extraction-free approaches enable streamlined sample prep but are severely impacted by inhibitors present in biological sample matrices. We previously reported the use of Hyperbaric Heating (HBH) for effective organism lysis and demonstrate here its effectiveness to prepare nucleic acids for PCR from various inhibitor-rich sample matrix types. Methods HBH exposes the sample to high temperature/high pressure environment for a short duration. This process effectively lyses organisms and denatures inhibitors within seconds. Samples are sealed within a pressure-tight metallic vessel, then rapidly heated using magnetic induction. Within the sealed metallic vessel, vaporization of the aqueous sample raises the internal pressure, enabling an internal temperature higher than 100°C. Proprietary sample processing beads containing chelating agents and other proteins protect nucleic acids from fragmentation during heating. Results The efficacy of HBH for PCR amplification was tested against commercial kits and extraction-free methods. HBH treatment of nasal swab samples spiked with inactivated SARS-CoV-2 elicited detection down to 125 viral copies/mL. Viruses such as RSV and Influenza spiked in nasal swab samples demonstrated comparable PCR results as extraction prepped samples. HBH treatment of microbe samples, including Candida albicans spiked in urine and Bacillus subtilis spiked in serum, had comparable PCR threshold cycles as microbe specific DNA extraction methods (Table 1). Conclusions HBH is a generalizable extraction-free nucleic acid sample prep technology affording detection capabilities comparable to commercial sample prep methods. We demonstrated the use of HBH sample prep for detection of several infectious microorganisms in common biological matrices (nasal swab, serum, urine) without additional sample purification. With its ease of use, speed, and lower cost, HBH will be a key tool in applications where nucleic acid amplification is pivotal for diagnostic and research use.

Ultra-early stage lower-grade gliomas: How can we define and differentiate these easily misdiagnosed gliomas through intraoperative molecular diagnosis.

Some lower-grade gliomas (LGG) are difficult to distinguish morphologically from glial cell proliferation or inflammatory changes during surgery, leading to a high risk of incorrect diagnosis. It is crucial to differentiate between the two for making surgical decisions. We define these critical cases as "ultra early stage lower-grade gliomas (UES-LGG)". We analyzed 11 out of 13 cases diagnosed with "gliosis" or "inflammatory changes" during surgery who tested positive for isocitrate dehydrogenase (IDH). Additionally, we conducted qRT-PCR detection on 35 samples diagnosed with LGG during surgery and analyzed their DNA content within an effective circulating threshold range to infer the critical value between UES-LGG and LGG. We conducted experiments using five standardized samples to infer the limited range of accurate detection of UES-LGG during surgery. In the comparative analysis of 11 samples and 35 samples, it was found that while there was no significant difference in the average DNA detection concentration between the two groups (159.36 ± 83.3 ng/μL and 146.83 ± 122.43 ng/μL), there was a notable statistical variance in the detection threshold for positive mutations (31.78 ± 1.14 and 26.14 ± 2.69, respectively). This suggests that the IDH mutation rate may serve as an indicator for differentiation between the two groups. Subsequently, DNA was extracted from standardized IDH mutant samples and subjected to gradient dilution for detection purposes. The results indicated a consistent increase in detection threshold as detection concentration decreased. When the detection concentration fell below <0.1 ng/μL, it became impossible to carry out effective threshold range detections. To further identify the precise detection interval, we conducted gradient division once again and sought to simulate the functional relationship between DNA copy number and cycle threshold within this interval. The research revealed that when the minimum detection concentration exceeded 250 copies/μL, a 100% detection rate could be achieved. This article defines UES-LGG as a tumor type easily misdiagnosed in clinical practice due to its extremely low positivity rate during surgery. The popularization of qRT-PCR based intraoperative molecular diagnosis greatly reduces errors caused by manual detection and improves disease detection rates during surgery. It provides a theoretical basis for more accurate surgical plans for surgeons.

Viral load dynamics in asymptomatic and symptomatic patients during Omicron BA.2 outbreak in Shanghai, China, 2022: a longitudinal cohort study

The SARS-CoV-2 virus, particularly the Omicron BA.2 variant, led to a significant surge in Shanghai, 2022. However, the viral load dynamic in Omicron infections with varying clinical severities remain unclear. This prospective cohort included 48,830 hospitalized coronavirus disease 2019 (COVID-19) patients across three hospitals in Shanghai, China, between 23 March and 15 May 2022. Systematic nucleic acid testing was performed using RT-PCR Cycle threshold (Ct) value as a proxy of viral load. We analyzed the kinetic characteristics of viral shedding by clinical severity and identified associated risk factors. The study comprised 31.06% asymptomatic cases, 67.66% mild-moderate cases, 1.00% severe cases, 0.29% critical and fatal cases. Upon admission, 57% of patients tested positive, with peak viral load observed at 4 days (median Ct value 27.5), followed by a decrease and an average viral shedding time (VST) of 6.1 days (Interquartile range, 4.0–8.8 days). Although viral load exhibited variation by age and clinical severity, peak Ct values occurred at similar times. Unvaccinated status, age exceeding 60, and comorbidities including hypertension, renal issues kidney dialysis and kidney transplantation, neurological disorders, rheumatism, and psychotic conditions were found to correlate with elevated peak viral load and extended VST. Asymptomatic cases demonstrated a 40% likelihood of contagiousness within 6 days of detection, while mild-moderate and severe cases exhibited post-symptom resolution infectious probabilities of 27% and over 50%, respectively. These findings revealed that the initial Ct values serve as a predictive indicator of severe outcomes. Unvaccinated elderly individuals with particular comorbidities are at high-risk for elevated viral load and prolonged VST.

One Health Investigation into Mpox and Pets, United States.

Monkeypox virus (MPXV) is zoonotic and capable of infecting many mammal species. However, whether common companion animals are susceptible to MPXV infection is unclear. During July 2022-March 2023, we collected animal and environmental swab samples within homes of confirmed human mpox case-patients and tested for MPXV and human DNA by PCR. We also used ELISA for orthopoxvirus antibody detection. Overall, 12% (22/191) of animal and 25% (14/56) of environmental swab samples from 4 households, including samples from 4 dogs and 1 cat, were positive for MPXV DNA, but we did not detect viable MPXV or orthopoxvirus antibodies. Among MPXV PCR-positive swab samples, 82% from animals and 93% from environment amplified human DNA with a statistically significant correlation in observed cycle threshold values. Our findings demonstrate likely DNA contamination from the human mpox cases. Despite the high likelihood for exposure, we found no indications that companion animals were infected with MPXV.

The Establishment of the Spiking Method to Evaluate the Rapid Diagnostic Test Antigen (Ag-RDT) Product for COVID-19 Detection

The quality control of the COVID-19 Rapid Diagnostic Test (Ag-RDT) product is regarded as one of the government’s responsibilities. The Indonesian government establishes rules for Ag-RDT post-market validation, where it should be performed by two designated laboratories, using the spiking technique. The usage of this technique raises concerns, especially if it does not represent the precise product quality, due to the sample dilution. In addition, the requisite of using fresh samples that should be prepared for less than 48 hours is considered costly and time-consuming. In response to this, we tested two samples from different age groups on the Ag-RDT brand recommended by the World Health Organization (WHO); Panbio™ Covid-19 Ag Rapid Test (Abbott) and standard Q Ag-RDT (SD Biosensor, Roche). In both Ag-RDT products, the samples observed in the cycle threshold (Ct) values≤25 groups exhibit &gt;80%sensitivity and &gt;97% specificity as in compliance with the WHO recommendation. Meanwhile, as observed in the Ct&gt;25 groups, the sensitivity of the two Ag-RDT products was below 25%, which was not in compliance with the WHO recommendation. Overall, this study indicated that the Spiking technique is eligible to be used for evaluating the performance of Ag-RDT, especially at Ct≤25. Additionally, the samples’ life span of up to 2 weeks of storage at -80oC can be used for post-market validation of Ag-RDT. Furthermore, the quality control assay for longer sample storage is interesting to be carried out.

Comparative Analysis of HPV Detection Efficiency: Evaluating Cobas 8800 Performance in Vaginal Self-Sampling versus Clinician-Collected Samples at a Regional Thai Hospital

Background: This study, conducted at a regional Thai hospital, assesses the comparative efficacy of self-collected versus clinician-collected samples for HPV detection using the Cobas 8800 system among Thai women aged 30–60. Methods: Our methodology involved analyzing 1541 self-collected and 1398 clinician-collected samples. Results: The results show a statistically significant mean difference in cycle threshold (Ct) values favoring clinician-collected samples (1.53; 95% CI: 1.18–1.87, p &lt; 0.0001). This pattern was consistent across various age groups, with the most pronounced differences noted in the oldest cohort (50–59 years), suggesting higher detection efficiency in clinician-collected samples. The study further explored the correlation of Ct values with cytological and histological outcomes, where clinician-collected samples demonstrated superior diagnostic performance, particularly in identifying LSIL and HSIL conditions, evidenced by AUC values of 0.793 and 0.866, respectively. While self-sampling remains a viable method, with sensitivity reaching up to 48.84% for LSIL and 46.15% for HSIL, clinician collection proved more accurate, likely influencing future national screening policies. Conclusions: This work underscores the need for robust sample collection methods and the importance of ongoing enhancements to self-sampling assays and techniques to ensure their efficacy in cervical cancer screening programs.

Amine-modified magnetic particles: An efficient tool for enhanced RNA extraction

Magnetic particles are an effective tool for simple, time-saving, and labour-saving nucleic acid extraction. In this study, we investigated the isolation of nucleic acids (NA) using 11 variants of magnetic nanoparticles (MPs, 52 ± 6.8 nm) with a surface concentration of amine groups up to 20.8 nmol · mg−1. All results were compared with morphologically identical magnetic material modified with SiO2 grafted with (3-aminopropyl)triethoxysilane (APTES). The properties of these materials were characterized by transmission electron microscopy, scanning electron microscopy, dynamic and electrophoretic light scattering, and magnetometry. Concentrations of amine groups on MPs-APTES were determined by the chemical bind and release method with photometric quantification.The isolation potential of the proposed materials toward NAs was evaluated using gel electrophoresis with photometric determination of NAs concentrations and RT-qPCR. Our results show that the NAs yields of MPs-APTES are higher than the reference MPs-SiO2, regardless of the amine group concentrations. Although the total yield decreased with the concentration of amine groups, a different affinity towards genomic DNA (gDNA) was observed. A high concentration of grafted amine groups induced a preference for ribosomal RNA (rRNA) over gDNA and mediated effective NA elution. Densitometric image analysis of gDNA bands showed that NAs isolated by MPs-SiO2 contained significantly higher DNA levels than MPs with 1/32 %, 1/2 %, and 16 % APTES modification, which was subsequently confirmed by qPCR. Gene expression analysis performed by RT-qPCR revealed that unwanted gDNA contamination did not significantly affect the threshold cycles (Ct) of target genes when cDNA-specific primers were used, but may lead to overestimation when targeting genes with low expression and no possibility to design cDNA-unique primers. From a practical point of view, MPs-APTES provided better dose-dependent NA isolation performance with stable NA quality.

The potential relationship between EasyNAT system Tt values and Cobas z480 Ct values in the detection of SARS-Cov-2

ObjectivesThis study aimed to evaluate the potential relationship between the time threshold (Tt) values of a commercial EasyNAT system, which is based on cross priming amplification (CPA) technology, and the cycle threshold (Ct) values of the Cobas z480 analyzer, which is based on a real-time fluorescence polymerase chain reaction (PCR) method, in the detection of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) from oropharyngeal swabs. Design and Methods: Data were retrospectively collected from a clinical laboratory between December 4, 2022 and July 1, 2024. ResultsA total of 277 EasyNAT-positive samples (Tt values from 3.83 to 29.5) were simultaneously investigated using the Cobas z480 analyzer (Ct values from 10.74 to 38.78). The concordance rate between the two systems was 100 %. Among the positive samples, the mean and maximum PCR Ct values of O and N genes increased in line with increasing Tt values of the left and right amplification areas of the EasyNAT system. The maximum Ct values of the O or N gene determined by the Cobas z480 analyzer were no more than 29.52 when the Tt values of the left or right amplification areas of the UC0116 analyzer were no more than 6. ConclusionsThe safe, simple, fast, accurate, and automatic EasyNAT system used in conjunction with a PCR system might be a better choice for the detection of SARS-CoV-2 in hospitals, especially in settings without sophisticated PCR facilities. The Tt value (≤6) of the EasyNAT system can be a reference index for estimating the maximum Ct value (29.52) in SARS-CoV-2-positive samples.

Quantitative real time PCR for distinction between Pneumocystis jirovecii infection/colonization in hospitalized patients.

Identification of the opportunistic fungus Pneumocystis jirovecii in respiratory specimens presents challenges, particularly in differentiating between colonization and active infection. The present study assessed a probe-based real time PCR (qPCR) diagnostic effectiveness in patients with diverse underlying conditions, particularly those with COVID-19 and pulmonary insufficiency. To set up the qPCR, clinical samples from 281 patients with respiratory ailments were tested. Subsequently, a descriptive study was conducted on 112 patients with pulmonary insufficiency with and without COVID-19 suspected of P. jirovecii infection. All specimens were subjected to DNA extraction followed by nested PCR and qPCR targeting the mitochondrial large subunit (mtLSU)-rRNA gene. Based on nested PCR and qPCR, P. jirovecii was identified in 40 out of 281 patients, with slight variations in positive samples observed across dilutions. Three patients who tested positive in nested PCR yielded negative results in probe-based qPCR. Conversely, three patients who tested positive in probe-based qPCR yielded negative results in nested PCR. Considering nested PCR as the golden standard, probe-based qPCR demonstrated good diagnostic performance, with 92.5% sensitivity and 98.7% specificity. Based on cycle threshold (Ct) values, the positive cases were categorized: ≤32 as infection, >35 as colonization, and a grey zone between these values (32 < X ≤ 35). The analysis of 112 PCP-suspected patients revealed a prevalence ranging from 6.25% (nested PCR) to 7% (probe-based qPCR). This study suggested Ct values to differentiate Pneumocystis pneumonia/colonization in immunocompromised patients. To further augment the diagnostic sensitivity, it is recommended to integrate qPCR results with clinical parameters and biomarkers to offer a more precise understanding of Pneumocystis-related conditions.

Assessment of the Effective Sensitivity of SARS-CoV-2 Sample Pooling Based on a Large-Scale Screening Experience: Retrospective Analysis.

The development of new large-scale saliva pooling detection strategies can significantly enhance testing capacity and frequency for asymptomatic individuals, which is crucial for containing SARS-CoV-2. This study aims to implement and scale-up a SARS-CoV-2 screening method using pooled saliva samples to control the virus in critical areas and assess its effectiveness in detecting asymptomatic infections. Between August 2020 and February 2022, our laboratory received a total of 928,357 samples. Participants collected at least 1 mL of saliva using a self-sampling kit and registered their samples via a smartphone app. All samples were directly processed using AutoMate 2550 for preanalytical steps and then transferred to Microlab STAR, managed with the HAMILTON Pooling software for pooling. The standard pool preset size was 20 samples but was adjusted to 5 when the prevalence exceeded 2% in any group. Real-time polymerase chain reaction (RT-PCR) was conducted using the Allplex SARS-CoV-2 Assay until July 2021, followed by the Allplex SARS-CoV-2 FluA/FluB/RSV assay for the remainder of the study period. Of the 928,357 samples received, 887,926 (95.64%) were fully processed into 56,126 pools. Of these pools, 4863 tested positive, detecting 5720 asymptomatic infections. This allowed for a comprehensive analysis of pooling's impact on RT-PCR sensitivity and false-negative rate (FNR), including data on positive samples per pool (PPP). We defined Ctref as the minimum cycle threshold (Ct) of each data set from a sample or pool and compared these Ctref results from pooled samples with those of the individual tests (ΔCtP). We then examined their deviation from the expected offset due to dilution [ΔΔCtP = ΔCtP - log2]. In this work, the ΔCtP and ΔΔCtP were 2.23 versus 3.33 and -0.89 versus 0.23, respectively, comparing global results with results for pools with 1 positive sample per pool. Therefore, depending on the number of genes used in the test and the size of the pool, we can evaluate the FNR and effective sensitivity (1 - FNR) of the test configuration. In our scenario, with a maximum of 20 samples per pool and 3 target genes, statistical observations indicated an effective sensitivity exceeding 99%. From an economic perspective, the focus is on pooling efficiency, measured by the effective number of persons that can be tested with 1 test, referred to as persons per test (PPT). In this study, the global PPT was 8.66, reflecting savings of over 20 million euros (US $22 million) based on our reagent prices. Our results demonstrate that, as expected, pooling reduces the sensitivity of RT-PCR. However, with the appropriate pool size and the use of multiple target genes, effective sensitivity can remain above 99%. Saliva pooling may be a valuable tool for screening and surveillance in asymptomatic individuals and can aid in controlling SARS-CoV-2 transmission. Further studies are needed to assess the effectiveness of these strategies for SARS-CoV-2 and their application to other microorganisms or biomarkers detected by PCR.

Exploring the relationship between cycle threshold values and oral manifestations in COVID-19: a comprehensive overview.

This cross-sectional study aimed to compare oral manifestations between severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)-positive and SARS-CoV-2-negative patients and to examine associations between oral symptoms, Ct values of E and N SARS-CoV-2 viral genes, and the implications of low Ct values indicating a high viral load, which is a predictive factor for the outcome of COVID-19. A total of 353 participating patients were aged ≥18 years with clinical manifestations of COVID-19 infection and tested for SARS-CoV-2 carriage at the medical center, by reverse transcriptase polymerase chain reaction (RT-PCR). All patients filled out an anonymous digital questionnaire regarding oral and general symptoms and overall medical health. Results: A significant association was found between SARS-CoV-2 carriage and dry mouth, unpleasant taste and changes in taste (p < 0.001); for example, 37.4% of the 147 SARS-CoV-2- positive participants had a dry mouth, compared to 18.9% of the 206 SARS-CoV-2- negative participants. Oral blisters were experienced by patients with an E gene Ct value of 10-20 (50%) or 21-30 (50%) (p = 0.041). Bad breath, dry mouth, unpleasant taste and changes in taste were mostly present in participants whose Ct values of both E and N genes were between 21 and 30. Conclusions: This study found significant associations between low Ct values of E and N SARS-CoV-2 viral genes and high viral load, indicating that Ct values can serve as predictive factors for COVID-19 outcomes. The findings suggest that while oral symptoms are present, the Ct values and associated high viral loads are more critical indicators of disease severity and prognosis.