Quantitative comparison of SARS-CoV-2 nucleic acid amplification test and antigen testing algorithms: a decision analysis simulation model

Background Antigen tests for SARS-CoV-2 offer advantages over nucleic acid amplification tests (NAATs, such as RT-PCR), including lower cost and rapid return of results, but show reduced sensitivity. Public health organizations recommend different strategies for utilizing NAATs and antigen tests. We sought to create a framework for the quantitative comparison of these recommended strategies based on their expected performance. Methods We utilized a decision analysis approach to simulate the expected outcomes of six testing algorithms analogous to strategies recommended by public health organizations. Each algorithm was simulated 50,000 times in a population of 100,000 persons seeking testing. Primary outcomes were number of missed cases, number of false-positive diagnoses, and total test volumes. Outcome medians and 95% uncertainty ranges (URs) were reported. Results Algorithms that use NAATs to confirm all negative antigen results minimized missed cases but required high NAAT capacity: 92,200 (95% UR: 91,200-93,200) tests (in addition to 100,000 antigen tests) at 10% prevalence. Selective use of NAATs to confirm antigen results when discordant with symptom status (e.g., symptomatic persons with negative antigen results) resulted in the most efficient use of NAATs, with 25 NAATs (95% UR: 13-57) needed to detect one additional case compared to exclusive use of antigen tests. Conclusions No single SARS-CoV-2 testing algorithm is likely to be optimal across settings with different levels of prevalence and for all programmatic priorities. This analysis provides a framework for selecting setting-specific strategies to achieve acceptable balances and trade-offs between programmatic priorities and resource constraints.

Quantitative Isothermal Amplification on Paper Membranes using Amplification Nucleation Site Analysis

Quantitative nucleic acid amplification tests (qNAATs) are critical in treating infectious diseases, such as in HIV viral load monitoring or SARS-CoV-2 testing, in which viral load indicates viral suppression or infectivity. Quantitative PCR is the gold standard tool for qNAATs; however, there is a need to develop point-of-care (POC) qNAATs to manage infectious diseases in outpatient clinics, low- and middle-income countries, and the home. Isothermal amplification methods are an emerging tool for POC NAATs as an alternative to traditional PCR-based workflows. Previous works have focused on relating isothermal amplification bulk fluorescence signals to input copies of target nucleic acids for sample quantification with limited success. In this work, we show that recombinase polymerase amplification (RPA) reactions on paper membranes exhibit discrete fluorescent amplification nucleation sites. We demonstrate that the number of nucleation sites can be used to quantify HIV-1 DNA and RNA in less than 20 minutes. An image-analysis algorithm quantifies nucleation sites and determines the input nucleic acid copies in the range of 67-3,000 copies per reaction. We demonstrate a mobile phone-based system for image capture and onboard processing, illustrating that this method may be used at the point-of-care for qNAATs with minimal instrumentation.

Optimal encephalitis/meningitis roadmap via precise diagnosis and treatment (IMPROVE): a study protocol for a randomized controlled trial

Background Encephalitis/meningitis brings a heavy disease burden, and the origin of disease remains unknown in 30–40% of patients. It is greatly significant that combinations of nucleic acid amplification and autoimmune antibody testing improves the diagnosis and treatment of encephalitis/meningitis. Moreover, though several diagnostic methods are in clinical use, a recognized and unified diagnosis and treatment process for encephalitis management remains unclear. Methods IMPROVE is a multicenter, open label, randomized controlled clinical trial that aims to evaluate the diagnostic performance, applications, and impact on patient outcomes of a new diagnostic algorithm that combines metagenomic next-generation sequencing (mNGS), multiplex polymerase chain reaction (PCR) and autoimmune antibody testing. The enrolled patients will be grouped into two parallel groups, multiplex PCR test plus autoimmune antibody group (Group I) or the mNGS plus autoimmune antibody group (Group II) with a patient ratio of 1:1. Both groups will be followed up for 12 months. The primary outcomes include the initial time of targeted treatment and the modified Rankin scale score on the 30th day of the trial. The secondary outcomes are the cerebrospinal fluid index remission rate on the 14th day, mortality rate on the 30th day, and an evaluation of diagnostic efficacy. The two groups are predicted to comprise of 484 people in total. Discussion To optimize the roadmap of encephalitis/meningitis, precise diagnosis, and treatment are of great significance. The effect of rapid diagnosis undoubtedly depends on the progression of new diagnostic tests, such as the new multiplex PCR, mNGS, and examination of broad-spectrum autoimmune encephalitis antibodies. This randomized-controlled study could allow us to obtain an accurate atlas of the precise diagnostic ability of these tests and their effect on the treatment and prognosis of patients. Trial registration ClinicalTrial.gov, NCT04946682. Registered 29 June 2021, ‘Retrospectively registered’, https://clinicaltrials.gov/ct2/show/NCT04946682?term=NCT04946682&draw=2&rank=1

Multiple Cross Displacement Amplification Coupled with Lateral Flow Biosensor (MCDA-LFB) for rapid detection of Legionella pneumophila

Background Legionella pneumophila is an opportunistic waterborne pathogen of significant public health problems, which can cause serious human respiratory diseases (Legionnaires’ disease). Multiple cross displacement amplification (MCDA), a isothermal nucleic acid amplification technique, has been applied in the rapid detection of several bacterial agents. In this report, we developed a MCDA coupled with Nanoparticles-based Lateral Flow Biosensor (MCDA-LFB) for the rapid detection of L. pneumophila. Results A set of 10 primers based on the L. pneumophila specific mip gene to specifically identify 10 different target sequence regions of L. pneumophila was designed. The optimal time and temperature for amplification are 57 min and 65 °C. The limit of detection (LoD) is 10 fg in pure cultures of L. pneumophila. No cross-reaction was obtained and the specificity of MCDA-LFB assay was 100%. The whole process of the assay, including 20 min of DNA preparation, 35 min of L. pneumophila-MCDA reaction, and 2 min of sensor strip reaction, took a total of 57 min (less than 1 h). Among 88 specimens for clinical evaluation, 5 (5.68%) samples were L. pneumophila-positive by MCDA-LFB and traditional culture method, while 4(4.55%) samples were L. pneumophila-positive by PCR method targeting mip gene. Compared with culture method, the diagnostic accuracy of MCDA-LFB method was higher. Conclusions In summary, the L. pneumophila-MCDA-LFB method we successfully developed is a simple, fast, reliable and sensitive diagnostic tool, which can be widely used in basic and clinical laboratories.

Isolation and Identification of a Rare Spike Gene Double-Deletion SARS-CoV-2 Variant From the Patient With High Cycle Threshold Value

Coronavirus disease 2019 (COVID-19) is an emerging life-threatening pulmonary disease caused by infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which originated in Wuhan, Hubei Province, China, in December 2019. COVID-19 develops after close contact via inhalation of respiratory droplets containing SARS-CoV-2 during talking, coughing, or sneezing by asymptomatic, presymptomatic, and symptomatic carriers. This virus evolved over time, and numerous genetic variants have been reported to have increased disease severity, mortality, and transmissibility. Variants have also developed resistance to antivirals and vaccination and can escape the immune response of humans. Reverse transcription polymerase chain reaction (RT–PCR) is the method of choice among diagnostic techniques, including nucleic acid amplification tests (NAATs), serological tests, and diagnostic imaging, such as computed tomography (CT). The limitation of RT–PCR is that it cannot distinguish fragmented RNA genomes from live transmissible viruses. Thus, SARS-CoV-2 isolation by using cell culture has been developed and makes important contributions in the field of diagnosis, development of antivirals, vaccines, and SARS-CoV-2 virology research. In this research, two SARS-CoV-2 strains were isolated from four RT–PCR-positive nasopharyngeal swabs using VERO E6 cell culture. One isolate was cultured successfully with a blind passage on day 3 post inoculation from a swab with a Ct > 35, while the cells did not develop cytopathic effects without a blind passage until day 14 post inoculation. Our results indicated that infectious SARS-CoV-2 virus particles existed, even with a Ct > 35. Cultivable viruses could provide additional consideration for releasing the patient from quarantine. The results of the whole genome sequencing and bioinformatic analysis suggested that these two isolates contain a spike 68-76del+spike 675-679del double-deletion variation. The double deletion was confirmed by amplification of the regions spanning the spike gene deletion using Sanger sequencing. Phylogenetic analysis revealed that this double-deletion variant was rare (one per million in public databases, including GenBank and GISAID). The impact of this double deletion in the spike gene on the SARS-CoV-2 virus itself as well as on cultured cells and/or humans remains to be further elucidated.

The Diagnostic Accuracy of One-Step Nucleic Acid Amplification for Lymph Node Metastases of Papillary Thyroid Carcinoma： A Systematic Review and Meta-Analysis

BackgroundOne-step nucleic acid amplification (OSNA) analysis is a molecular diagnostic technique for lymph node metastases (LNMs) by quantifying cytokeratin 19(CK 19) mRNA. We aim to evaluate the intraoperative diagnostic accuracy of OSNA assay for LNMs of papillary thyroid carcinoma (PTC).MethodsPubMed, Embase, Cochrane Library, and Web of Science databases were searched to retrieve related literature. A meta-analysis was performed using STATA11.0, Meta-Disc 1.4 and RevMan 5.3.ResultsThis meta-analysis included six studies involving 987 lymph nodes from 194 patients. The pooled sensitivity, specificity, and area under the summary receiver-operating characteristic curve (AUC) of OSNA for detecting LNM were 0.88, 0.90, and 0.95, respectively.ConclusionOSNA assay is an accurate molecular diagnosis for intraoperative detection of lymph node metastasis in PTC.

Identification of bacteria strains using the Recombinase Polymerase Amplification assay on a miniaturized solid-state pH sensor

Rapid identification of bacteria based on nucleic acid amplification allows dealing with the detection of pathogens in clinical, food, and environmental samples. Amplification products must be detected and analyzed by external devices or integrated complicated optical systems. Here, we developed a solid-state pH electrode based on iridium oxide (IrO2) films to measure released hydrogen ions (H+) from isothermal nucleic acid (NA) amplification of bacterial samples. By recombinase polymerase amplification (RPA), we achieved rapid (< 15 min) and sensitive (<30 copies) detection with an accuracy of about 0.03 pH. The RPA-based hydrogen ion sensing assay shows higher specificity, sensitivity, and efficiency as the same polymerase chain reaction (PCR) methods. We initially used the RPA-based sensor to detect E. coli species in laboratory samples. Among, 27 random laboratory samples of E. coli samples, 6 were found to be DH5alpha, 9 BL21, 3 HB101, 6 TOP10, and 3 JM109. The electrical detection of amplification provides generally applicable techniques for the detection of nucleic acid amplification, enabling molecular diagnostic tests in the field and integrating data transmission to the mobile device. These results can be future developed into an efficient tool for rapid on-site detection of bacterial pathogens in clinical samples.

Rapid, instrument-free colorimetric quantification of DNA using Nile Blue

The use of nucleic acid tests (NAT) for sensitive and rapid detection of pathogens relevant to human health has increased due to the ubiquity of nucleic acid amplification techniques such...