SMaRT-PCR: sampling using masks and RT-PCR, a non-invasive diagnostic tool for paediatric pulmonary TB.

Key challenges in paediatric TB diagnosis are invasive sampling and poor sensitivity of standard methods. This study demonstrates the diagnostic potential of non-invasive sampling of bioaerosols from children using SMaRT-PCR, comprising mask sampling combined with reverse transcriptase-polymerase chain reaction (RT-PCR) for TB.Exhaled bioaerosols were captured on modified N-95 masks in a 10-min talk-cough-breathe process from 51 children (30 with TB confirmed using standard sampling methods and 21 without TB) aged 2-15 years. All mask samples were tested using in-house RT-PCR for 16s and rpoB RNA transcripts. Additional mask samples from children with TB were tested using Xpert® MTB/RIF (n = 3) and Xpert® MTB/RIF Ultra (n = 27).SMaRT-PCR sensitivity for detecting TB among treatment-naïve children was 96% if 16s or rpoB was present, and 75% if both genes were present, comparable to standard methods (71%) in the same cohort. Specificity was better for both genes, at 95%, than 85% for a single gene detection. Mask sampling with Xpert MTB/RIF or Ultra had a sensitivity of only 13%.This is the first study to provide evidence for testing bioaerosols as a promising alternative for detecting paediatric TB. Sampling is non-invasive and simple, with the potential for point-of-care applications. This pilot study also suggests that RNA transcript-based detection may improve TB diagnostic sensitivity in children; however, further investigation is required to establish its adaptability in clinical settings..

EndoGeneAnalyzer: A tool for selection and validation of reference genes.

The selection of proper reference genes is critical for accurate gene expression analysis in all fields of biological and medical research, mainly because there are many distinctions between different tissues and specimens. Given this variability, even in known classic reference genes, demands of a comprehensive analysis platform is needed to identify the most suitable genes for each study. For this purpose, we present an analysis tool for assisting in decision-making in the analysis of reverse transcription-quantitative polymerase chain reaction (RT-qPCR) data. EndoGeneAnalyzer, an open-source web tool for reference gene analysis in RT-qPCR studies, was used to compare the groups/conditions under investigation. This interactive application offers an easy-to-use interface that allows efficient exploration of datasets. Through statistical and stability analyses, EndoGeneAnalyzer assists in the select of the most appropriate reference gene or set of genes for each condition. It also allows researchers to identify and remove unwanted outliers. Moreover, EndoGeneAnalyzer provides a graphical interface to compare the evaluated groups, providing a visually informative differential analysis.

Analysis of Suspected Measles Cases with Discrepant Measles-Specific IgM and rRT-PCR Test Results, Japan.

We investigated clinically suspected measles cases that had discrepant real-time reverse transcription PCR (rRT-PCR) and measles-specific IgM test results to determine diagnoses. We performed rRT-PCR and measles-specific IgM testing on samples from 541 suspected measles cases. Of the 24 IgM-positive and rRT-PCR--negative cases, 20 were among children who received a measles-containing vaccine within the previous 6 months; most had low IgG relative avidity indexes (RAIs). The other 4 cases were among adults who had an unknown previous measles history, unknown vaccination status, and high RAIs. We detected viral nucleic acid for viruses other than measles in 15 (62.5%) of the 24 cases with discrepant rRT-PCR and IgM test results. Measles vaccination, measles history, and contact history should be considered in suspected measles cases with discrepant rRT-PCR and IgM test results. If in doubt, measles IgG avidity and PCR testing for other febrile exanthematous viruses can help confirm or refute the diagnosis.

Epidemiological and molecular surveillance of norovirus in the Brazilian Amazon: description of recombinant genotypes and improvement of evolutionary analysis.

Noroviruses are highly infectious, genetically diverse viruses. Global outbreaks occur frequently, making molecular surveillance important for infection monitoring. This cross-sectional descriptive study aimed to monitor cases of norovirus gastroenteritis in the Brazilian Amazon. Fecal samples were tested by immunoenzymatic assay, RT-PCR and genetic sequencing for the ORF1/ORF2 and protease regions. Bayesian inference with a molecular clock was employed to construct the phylogeny. The norovirus prevalence was 25.8%, with a higher positivity rate among children aged 0-24 months. Genogroup GII accounted for 98.1% of the sequenced samples, while GI accounted for 1.9% of them. The GII.P16/GII.4 genotype was the most prevalent, with an evolution rate of 2.87x10-3 and TMRCA estimated in 2012. This study demonstrates that norovirus is a primary causative agent of gastroenteritis and provides data on viral genetic diversity that may facilitate infection surveillance and vaccine development.

Evaluation of different genomic regions of rotavirus B and rotavirus C for development of real-time RT‒PCR assays.

BACKGROUND: The causative agents of diarrhea, rotavirus B (RVB) and rotavirus C (RVC) are common in adults and patients of all age groups, respectively. Due to the Rotavirus A (RVA) vaccination program, a significant decrease in the number of gastroenteritis cases has been observed globally. The replacement of RVA infections with RVB, RVC, or other related serogroups is suspected due to the possibility of reducing natural selective constraints due to RVA infections. The data available on RVB and RVC incidence are scant due to the lack of cheap and rapid commercial diagnostic assays and the focus on RVA infections. The present study aimed to develop real-time RT‒PCR assays using the data from all genomic RNA segments of human RVB and RVC strains available in the Gene Bank. RESULTS: Among the 11 gene segments, NSP3 and NSP5 of RVB and the VP6 gene of RVC were found to be suitable for real-time RT‒PCR (qRT‒PCR) assays. Fecal specimens collected from diarrheal patients were tested simultaneously for the presence of RVB (n = 192) and RVC (n = 188) using the respective conventional RT‒PCR and newly developed qRT‒PCR assays. All RVB- and RVC-positive specimens were reactive in their respective qRT‒PCR assays and had Ct values ranging between 23.69 and 41.97 and 11.49 and 36.05, respectively. All known positive and negative specimens for other viral agents were nonreactive, and comparative analysis showed 100% concordance with conventional RT‒PCR assays. CONCLUSIONS: The suitability of the NSP5 gene of RVB and the VP6 gene of RVC was verified via qRT‒PCR assays, which showed 100% sensitivity and specificity. The rapid qRT‒PCR assays developed will be useful diagnostic tools, especially during diarrheal outbreaks for testing non-RVA rotaviral agents and reducing the unnecessary use of antibiotics.

Development and Validation of Three Triplex Real-Time RT-PCR Assays for Typing African Horse Sickness Virus: Utility for Disease Control and Other Laboratory Applications.

The African horse sickness virus (AHSV) belongs to the Genus Orbivirus, family Sedoreoviridae, and nine serotypes of the virus have been described to date. The AHSV genome is composed of ten linear segments of double-stranded (ds) RNA, numbered in decreasing size order (Seg-1 to Seg-10). Genome segment 2 (Seg-2) encodes outer-capsid protein VP2, the most variable AHSV protein and the primary target for neutralizing antibodies. Consequently, Seg-2 determines the identity of the virus serotype. An African horse sickness (AHS) outbreak in an AHS-free status country requires identifying the serotype as soon as possible to implement a serotype-specific vaccination program. Considering that nowadays 'polyvalent live attenuated' is the only commercially available vaccination strategy to control the disease, field and vaccine strains of different serotypes could co-circulate. Additionally, in AHS-endemic countries, more than one serotype is often circulating at the same time. Therefore, a strategy to rapidly determine the virus serotype in an AHS-positive sample is strongly recommended in both epidemiological situations. The main objective of this study is to describe the development and validation of three triplex real-time RT-PCR (rRT-PCR) methods for rapid AHSV serotype detection. Samples from recent AHS outbreaks in Kenia (2015-2017), Thailand (2020), and Nigeria (2023), and from the AHS outbreak in Spain (1987-1990), were included in the study for the validation of these methods.

Development and Evaluation of an In-House Real-Time RT-PCR Targeting nsp10 Gene for SARS-CoV-2 Detection.

The emergence of SARS-CoV-2 mutations poses significant challenges to diagnostic tests, as these mutations can reduce the sensitivity of commonly used RT-PCR assays. Therefore, there is a need to design diagnostic assays with multiple targets to enhance sensitivity. In this study, we identified a novel diagnostic target, the nsp10 gene, using nanopore sequencing. Firstly, we determined the analytical sensitivity and specificity of our COVID-19-nsp10 assay. The COVID-19-nsp10 assay had a limit of detection of 74 copies/mL (95% confidence interval: 48-299 copies/mL) and did not show cross-reactivity with other respiratory viruses. Next, we determined the diagnostic performance of the COVID-19-nsp10 assay using 261 respiratory specimens, including 147 SARS-CoV-2-positive specimens belonging to the ancestral strain and Alpha, Beta, Gamma, Delta, Mu, Eta, Kappa, Theta and Omicron lineages. Using a LightMix E-gene RT-PCR assay as the reference method, the diagnostic sensitivity and specificity of the COVID-19-nsp10 assay were found to be 100%. The median Cp values for the LightMix E-gene RT-PCR and our COVID-19-nsp10 RT-PCR were 22.48 (range: 12.95-36.60) and 25.94 (range 16.37-36.87), respectively. The Cp values of the COVID-19-nsp10 RT-PCR assay correlated well with those of the LightMix E-gene RT-PCR assay (Spearman's ρ = 0.968; p < 0.0001). In conclusion, nsp10 is a suitable target for a SARS-CoV-2 RT-PCR assay.

Diagnostic accuracy of direct reverse transcription-polymerase chain reaction using guanidine-based and guanidine-free inactivators for SARS-CoV-2 detection in saliva samples.

This study aimed to evaluate diagnostic accuracy of SARS-CoV-2 RNA detection in saliva samples treated with a guanidine-based or guanidine-free inactivator, using nasopharyngeal swab samples (NPS) as referents. Based on the NPS reverse transcription-polymerase chain reaction (RT-PCR) results, participants were classified as with or without COVID-19. Fifty sets of samples comprising NPS, self-collected raw saliva, and saliva with a guanidine-based, and guanidine-free inactivator were collected from each group. In patients with COVID-19, the sensitivity of direct RT-PCR using raw saliva and saliva treated with a guanidine-based and guanidine-free inactivator was 100.0%, 65.9%, and 82.9%, respectively, with corresponding concordance rates of 94.3% (κ=88.5), 82.8% (κ=64.8), and 92.0% (κ=83.7). Among patients with a PCR Ct value of <30 in the NPS sample, the positive predictive value for the three samples was 100.0%, 80.0%, and 96.0%, respectively. The sensitivity of SARS-CoV-2 RNA detection was lower in inactivated saliva than in raw saliva and lower in samples treated with a guanidine-based than with a guanidine-free inactivator. However, in individuals contributing to infection spread, inactivated saliva showed adequate accuracy regardless of the inactivator used. Inactivators can be added to saliva samples collected for RT-PCR to reduce viral transmission risk while maintaining adequate diagnostic accuracy.

Nuclear Transcription Factor Detection.

Cellular fate is determined by the activity of nuclear transcription factors. Here, we describe a series of protocols for detecting transcription factors at both the transcript and protein levels in human adipose cells. Methods for analysis of transcript include RNA extraction, reverse transcription polymerase chain reaction (RT-PCR), endpoint PCR, and RT-qPCR. Evaluation of protein expression includes protocols for protein extraction, quantification by Bradford assay, SDS-PAGE, western blotting, and quantification with ImageJ. Each of these steps is critical for a reliable and reproducible assessment of transcription expression and characterization of human adult-derived adipose stromal/stem cells.

Validation of Endogenous Control Genes by Real-Time Quantitative Reverse Transcriptase Polymerase Chain Reaction for Acute Leukemia Gene Expression Studies.

Reference genes are used as internal reaction controls for gene expression analysis, and for this reason, they are considered reliable and must meet several important criteria. In view of the absence of studies regarding the best reference gene for the analysis of acute leukemia patients, a panel of genes commonly used as endogenous controls was selected from the literature for stability analysis: Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), Abelson murine leukemia viral oncogene human homolog 1 (ABL), Hypoxanthine phosphoribosyl-transferase 1 (HPRT1), Ribosomal protein lateral stalk subunit P0 (RPLP0), ß-actin (ACTB) and TATA box binding protein (TBP). The stability of candidate reference genes was analyzed according to three statistical methods of assessment, namely, NormFinder, GeNorm and R software (version 4.0.3). From this study's analysis, it was possible to identify that the endogenous set composed of ACTB, ABL, TBP and RPLP0 demonstrated good performances and stable expressions between the analyzed groups. In addition to that, the GAPDH and HPRT genes could not be classified as good reference genes, considering that they presented a high standard deviation and great variability between groups, indicating low stability. Given these findings, this study suggests the main endogenous gene set for use as a control/reference for the gene expression in peripheral blood and bone marrow samples from patients with acute leukemias is composed of the ACTB, ABL, TBP and RPLP0 genes. Researchers may choose two to three of these housekeeping genes to perform data normalization.

TUMOR MARKERS EXPRESSION LEVELS IN GASTRIC CANCER PATIENT'S PERIPHERAL BLOOD BY RT-PCR ASSESSMENT.

BACKGROUND: Hematological recurrence is the second most frequent cause of failure in the treatment of gastric cancer. The detection of circulating tumor markers in peripheral blood by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) method may be a useful tool to predict recurrence and determine the patient's prognosis. However, no consensus has been reached regarding the association between the tumor markers level in peripheral blood and its impact on patient survival. AIMS: To evaluate the expression of the circulating tumor markers CK20 and MUC1 in peripheral blood samples from patients with gastric cancer by qRT-PCR, and to verify the association of their expression levels with clinicopathological characteristics and survival. METHODS: A total of 31 patients with gastric adenocarcinoma were prospectively included in this study. CK20 and MUC1 expression levels were analyzed from peripheral blood by the qRT-PCR technique. RESULTS: There was no statistically significant (p>0.05) association between CK20 expression levels and clinical, pathological, and surgical features. Higher MUC1 expression levels were associated with female patients (p=0.01). There was a correlation between both gene levels (R=0.81, p<0.001), and CK20 level and tumor size (R=0.39, p=0.034). CONCLUSIONS: CK20 and MUC1 expression levels could be assessed by qRT-PCR from total peripheral blood samples of patients with gastric cancer. CK20 levels were correlated to MUC1 levels as well as to tumor size. There was no difference in disease-free survival and overall survival regarding both genetic markers expression in this series.

Molecular Amplification and Cell Culturing Efficiency for Enteroviruses' Detection in Cerebrospinal Fluids of Algerian Patients Suffering from Meningitis.

Enteroviruses (EVs) represent a major cause of viral meningitis, being responsible for nearly 1 billion infections each year worldwide. Several techniques were developed to obtain better diagnostic results of EV infections. Herein, we evaluated the efficiency of EV detection through isolation on both Rhabdomyosarcoma (RD) and Vero cell line cultures, conventional reverse transcription-polymerase chain reaction (RT-PCR) and real-time RT-PCR. Thus, 50 cerebrospinal fluid (CSF) samples belonging to patients suspected to have viral meningitis in northern Algeria were collected, anonymously numbered from 1 to 50 and subjected to the above-mentioned techniques for EV detection. Using real-time RT-PCR, 34 CSF samples were revealed to be positive for viral origin of meningitis (68%). Thirteen of them were positive when the conventional RT-PCR was used (26%), and only three samples gave positive results when the cell culture technique was used (6%). Surprisingly, two cell culture-positive CSF samples, namely, 31 and 39, were negative using RT-PCR directly on the original samples. However, they turned to be positive when amplification was carried out on their corresponding cell culture supernatant. The cell-cultured viral isolates were then identified by sequencing their viral genome's VP1 regions. All of them were revealed to belong to the echovirus 27 strain. This investigation demonstrates that RT-PCR techniques are often more sensitive, accurate and much faster, providing reliable results within a clinically acceptable timeframe. However, viral isolation on cell cultures remains crucial to obtain enough viral load for serological tests or even to avoid the rare, but existing, false negative PCR.

Identification of a measles variant displaying mutations impacting molecular diagnostics, Geneva, Switzerland, 2023.

Real-time PCR is one of the most widely used techniques to diagnose measles cases. Here we report measles virus variants with three genetic mutations in the reverse primer annealing site of a widely used PCR. The mutations result in a slight loss of the PCR sensitivity. Variants bearing the three mutations presently circulate in different countries since at least the end of 2021. Our findings highlight the usefulness of molecular surveillance in monitoring if oligonucleotides in diagnostic tests remain adequate.

RT-PCR genotyping assays to identify SARS-CoV-2 variants in England in 2021: a design and retrospective evaluation study.

BACKGROUND: Whole-genome sequencing (WGS) is the gold standard diagnostic tool to identify and genetically characterise emerging pathogen mutations (variants), but cost, capacity, and timeliness limit its use when large populations need rapidly assessing. We assessed the potential of genotyping assays to provide accurate and timely variant information at scale by retrospectively examining surveillance for SARS-CoV-2 variants in England between March and September, 2021, when genotyping assays were used widely for variant detection. METHODS: We chose a panel of four RT-PCR genotyping assays to detect circulating variants of SARS-COV-2 in England and developed a decision algorithm to assign a probable SARS-CoV-2 variant to samples using the assay results. We extracted surveillance data from the UK Health Security Agency databases for 115 934 SARS-CoV-2-positive samples (March 1-Sept 6, 2021) when variant information was available from both genotyping and WGS. By comparing the genotyping and WGS variant result, we calculated accuracy metrics (ie, sensitivity, specificity, and positive predictive value [PPV]) and the time difference between the sample collection date and the availability of variant information. We assessed the number of samples with a variant assigned from genotyping or WGS, or both, over time. FINDINGS: Genotyping and an initial decision algorithm (April 10-May 11, 2021 data) were accurate for key variant assignment: sensitivities and PPVs were 0·99 (95% CI 0·99-0·99) for the alpha, 1·00 (1·00-1·00) for the beta, and 0·91 (0·80-1·00) for the gamma variants; specificities were 0·97 (0·96-0·98), 1·00 (1·00-1·00), and 1·00 (1·00-1·00), respectively. A subsequent decision algorithm over a longer time period (May 27-Sept 6, 2021 data) remained accurate for key variant assignment: sensitivities were 0·91 (95% CI 0·74-1·00) for the beta, 0·98 (0·98-0·99) for the delta, and 0·93 (0·81-1·00) for the gamma variants; specificities were 1·00 (1·00-1·00), 0·96 (0·96-0·97), and 1·00 (1·00-1·00), respectively; and PPVs were 0·83 (0·62-1·00), 1·00 (1·00-1·00), and 0·78 (0·59-0·97), respectively. Genotyping produced variant information a median of 3 days (IQR 2-4) after the sample collection date, which was faster than with WGS (9 days [8-11]). The flexibility of genotyping enabled a nine-times increase in the quantity of samples tested for variants by this method (from 5000 to 45 000). INTERPRETATION: RT-PCR genotyping assays are suitable for high-throughput variant surveillance and could complement WGS, enabling larger scale testing for known variants and timelier results, with important implications for effective public health responses and disease control globally, especially in settings with low WGS capacity. However, the choice of panels of RT-PCR assays is highly dependent on database information on circulating variants generated by WGS, which could limit the use of genotyping assays when new variants are emerging and spreading rapidly. FUNDING: UK Health Security Agency and National Institute for Health Research Health Protection Research Unit in Emergency Preparedness and Response.

In-house RT-PCR detection of hepatitis A virus in human plasma pools used for the manufacture of medicinal products.

Hepatitis A virus (HAV) is the most frequent cause of viral hepatitis worldwide and is transmitted through the fecal-oral route. However, HAV can also be transmitted by blood-derived products. This is due to the fact that viremia occurs during the asymptomatic phase of HAV infection, enabling infected blood or plasma donations to occur. Viral inactivation/removal steps are included during manufacturing of plasmaderived products. However, HAV is a small non-enveloped virus very difficult to remove with traditional viral inactivation procedures. To accomplish European guidelines for pooled human plasma (treated for virus inactivation), plasma manufacturers have been implementing HAV nucleic acid test (NAT) screening on plasma pools. In this study, we validate an in-house multiplex reverse-transcription real-time PCR (RT-PCR) assay targeting HAV RNA and an internal control with hydrolysis probes for amplicon detection. The HAV RNA test was validated by assessing limit of detection, robustness, sensitivity and specificity according to European Pharmacopoeia (Ph. Eur.) guidelines. Our assay is able to detect 100 IU/mL of all human HAV genotypes that have been described so far. The multiplex assay shows remarkable sensitivity with a 95% lower limit of detection of 5.2 IU/mL. Also, our HAV test shows good robustness, precision, and specificity. We conclude that our assay broadly meets the requirements for its purpose. The implementation of this test in the production process of plasma-derived products will increase their safety.

Monitoring SARS-CoV-2 genetic variability: A post-market surveillance workflow for combined bioinformatic and laboratory evaluation of commercial RT-PCR assay performance.

OBJECTIVE: The speed at which Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) is mutating has made it necessary to frequently assess how these genomic changes impact the performance of diagnostic real-time polymerase chain reaction (RT-PCR) assays. Herein, we describe a generic three-step workflow to assess the effect of genomic mutations on inclusivity and sensitivity of RT-PCR assays. METHODS: Sequences collected from the Global Initiative on Sharing All Influenza Data (GISAID) were mapped to a SARS-CoV-2 reference genome to evaluate the position and prevalence of mismatches in the oligonucleotide-binding sites of the QIAstat-Dx, an RT-PCR panel designed to detect SARS-CoV-2. The frequency of mutations and their impact on melting temperature were assessed, and sequences flagged by risk-based criteria were examined in vitro. RESULTS: Out of 8,900,393 SARS-CoV-2 genome sequences analyzed, only 173 (0.0019%) genomes contained potentially critical mutations for the QIAstat-Dx; follow-up in-vitro testing confirmed no impact on the assays' performance. CONCLUSIONS: The current study demonstrates that SARS-CoV-2 genetic variants do not affect the performance of the QIAstat-Dx device. It is recommended that manufacturers incorporate this workflow into obligatory post-marketing surveillance activities, as this approach could potentially enhance genetic monitoring of their product.

Optimization of an allelic discrimination real-time RT-PCR assay for detection of H275Y oseltamivir resistance gene mutation among influenza A(H1N1)pdm09 patients from 2020 to 2022.

Influenza virus is known to cause mild to severe respiratory infections and is also prone to genetic mutations. Of all the mutations, neuraminidase (NA) gene mutations are a matter of concern, as most approved antivirals target this protein. During the 2020 influenza season, an emergence of mutation in the NA gene, affecting the binding of the World Health Organization (WHO)-recommended probes to the specific site of the NA gene, was reported by our group. As a result of this mutation, the WHO-recommended allelic discrimination real-time reverse transcriptase polymerase chain reaction (RT-PCR) assay was unable to detect wild-type (H275) or mutant oseltamivir-resistant (Y275) strains of influenza A(H1N1)pmd09 viruses. In the current study, the WHO-recommended probes were redesigned according to the mutation in the probe binding site. Fifty undetermined samples (2020-2021) from the previous study were retested with the newly designed probes and found to be positive for H275 and/or Y275. The results obtained were similar to the Sanger sequencing results from the previous study, suggesting that the redesigned probes were efficient in discriminating between wild-type and mutant-type viruses. Furthermore, 133 samples from 2022, making a total of 183 samples (2020-2022), were tested using improved allelic discrimination real-time RT-PCR, and the overall prevalence rate of oseltamivir resistance in 2020-2022 was found to be 0.54%.

Direct detection of canine picornavirus complete coding sequence in wastewater using long-range reverse-transcriptase polymerase chain reaction and long-read sequencing.

We describe four complete coding sequence (cCDS) of canine picornavirus from wastewater in Arizona, USA detected by coupling cCDS single-contig (∼7.5 kb) reverse-transcriptase polymerase chain reaction (RT-PCR) and low-cost long-read high-throughput sequencing. For viruses of medical/veterinary importance, this workflow expands possibilities of wastewater based genomic epidemiology for exploring virus evolutionary dynamics especially in low-resource settings.

Selection of suitable reference genes for gene expression studies in HMC3 cell line by quantitative real-time RT-PCR.

Microglia represent the primary immune defense system within the central nervous system and play a role in the inflammatory processes occurring in numerous disorders, such as Parkinson's disease (PD). PD onset and progression are associated with factors considered possible causes of neuroinflammation, i.e. genetic mutations. In vitro models of microglial cells were established to identify specific molecular targets in PD through the analysis of gene expression data. Recently, the Human Microglial Clone 3 cell line (HMC3) has been characterized and a new human microglia model has emerged. Here we perform RT-qPCR analyses to evaluate the expression of ten reference genes in HMC3, untreated or stimulated to a pro-inflammatory status. The comparative ∆CT method, BestKeeper, Normfinder, geNorm and RefFinder algorithms were used to assess the stability of the candidate genes. The results showed that the most suitable internal controls are HPRT1, RPS18 and B2M genes. In addition, the most stable and unstable reference genes were used to normalize the expression of a gene of interest in HMC3, resulting in a difference in the statistical significance in cells treated with Rotenone. This is the first reference gene validation study in HMC3 cell line in pro-inflammatory status and can contribute to more reliable gene expression analysis in the field of neurodegenerative and neuroinflammatory research.

Cycle threshold of SARS-CoV-2 RT-PCR as a driver of retesting.

SARS-CoV-2 RT-PCR is a critical and, at times, limited resource. Frequent Retesting of patients may strain testing infrastructure unduly. Recommendations that include cycle threshold (Ct) cutoffs may incentivize early retesting when the Ct value is reported. We aimed to investigate patterns of retesting in association with initial Ct-values. We performed a retrospective analysis of RT-PCR results (including Ct-values) for patients from whom ≥ 2 samples were collected within 14 days, the first of which had to be positive. We calculated absolute and baseline-corrected kinetics of Ct-values over time, as well as the median initial Ct-values in dependence of the timing of the first retesting and the time until RT-PCR negativity for SARS-CoV-2. Retesting after an initial positive SARS-CoV-2 RT-PCR was most commonly performed on day 7, with patients being retested as early as day 1. The majority of patients retested within 14 days remained SARS-CoV-2 positive in the RT-PCR. Baseline-corrected Ct-values showed a quasi-linear increase over 14 days since the initial positive result. Both the timing until the first retesting and until RT-PCR negativity were inversely correlated with the initial Ct-value. The timing of retesting after a positive SARS-CoV-2 RT-PCR appears to be significantly influenced by the initial Ct-value. Although it can be assumed that Ct-values will increase steadily over time, strategies that rely on rigid Ct-cutoffs should be discussed critically, not only because of methodological caveats but also because of the strain on testing infrastructure caused by the incentive for early retesting that Ct-values apparently represent.