Research Advance on Smartphone-based Visual Biosensor in Point-of-Care Testing / 分析化学

Human physiological indicators have become an important standard for assessing health in modern society.Traditional detection methods often require a separate laboratory,complex operation process and long detection time,so it is urgent to develop portable,fast and accurate on-site detection technologies for bioanalysis.Point-of-care testing(POCT),which differs from traditional laboratory testing,can realize the rapid in situ detection of biomarkers without the complicated analytical process of the laboratory.Smartphones,which are an essential tool in our daily life,not only have independent operating systems and built-in storage functions,but also have high-definition cameras,which have great application potential in POCT visualization.The combination of various biosensing technologies and smartphones has developed into a new direction in the field of POCT.This review mainly introduced the research progress of smartphone-based visual biosensors in POCT in recent years,including colorimetric sensors,fluorescence sensors,chemiluminescence sensors and electrochemiluminescence sensors.Finally,the problems faced by smart-phone-based visual biosensors in the application of POCT were summarized,and their future development was prospected.

Evaluation of molecular point-of-care testing for rapid diagnosis of influenza A virus and influenza B virus / 国际检验医学杂志

Objective To evaluate the performance of two molecular point-of-care testing(POCT)prod-ucts in the diagnosis of influenza A virus(Flu A)and influenza B virus(Flu B)of clinical samples,and pre-liminarily evaluate the clinical diagnostic value of the changes of infection-related indicators in peripheral blood.Methods A total of 491 oropharyngeal swabs from patients with influenza-like symptoms who were treated in the hospital were recruited into this study from November 1,2019 to June 30,2023.These swabs were collected using reverse transcription real-time quantitative fluorescent polymerase chain reaction(RT-qPCR),and two POCT molecular products,XpertTM Xpress Flu/RSV and EasyNAT? Flu Assay,respectively.The diagnostic performance of two POCT molecular products was analyzed using RT-qPCR reaction as a standard.According to the results of RT-qPCR method,the subjects were divided into Flu A positive group,Flu B positive group and negative group(both Flu A and Flu B were negative).The levels of indicators in pe-ripheral blood of the three groups were compared to evaluate the value of these indicators in the clinical diag-nosis of Flu A and Flu B.Results Among the 491 patient specimens,the XpertTM Xpress Flu/RSV assay showed the sensitivity for Flu A was 96.88%,and the specificity was 99.75%,and the sensitivity for Flu B was 100.00%,and the specificity was 100.00%.EasyNAT? Flu Assay assay showed the sensitivity for Flu A was 94.79%,and the specificity was 96.81%,and the sensitivity for Flu B was 100.00%,and the specificity was 100.00%.And two POCT molecular methods performed well consistency(Kappa value was 0.974).There was no significant difference in the levels of C-reactive protein and serum amyloid A among the negative group,Flu A positive group,and Flu B positive group(P>0.05).But the levels of white blood cell count in the negative group were higher than those in the Flu A positive group and Flu B positive group(P<0.01).Conclusion In this paper,two typical molecular POCT products are studied.Their sensitivity and specificity are highly consistent with the results of RT-qPCR.Molecular POCT products have the advantages of flexibil-ity and rapidity,which are of great value for the improvement of clinical diagnosis and treatment.Molecular detection combined with peripheral blood infection related indicators is helpful for the early diagnosis of influ-enza virus infectious diseases.

Application and Prospect of Pre-transfusion Detection Technology / 生物化学与生物物理进展

Blood transfusion accuracy is crucial for disease treatment and emergency rescue. Prior to a blood transfusion, it is essential to perform a number of tests to assure proper clinical treatment and reduce the risk of complications. Pre-transfusion testing refers primarily to the blood group, coagulation, and infection to assure transfusion safety and prevent cross-infection. Blood type, cross-matching blood, fibrinogen, viral hepatitis, human immunodeficiency virus, and syphilis are routine pre-transfusion tests. Immunoassay is the traditional clinical pretransfusion detection method. With the expansion of clinical treatment requirements from hospital to on-site treatment, new technologies, such as electrochemical sensing, microfluidics, and spectroscopy technology, are being developed gradually for rapid detection prior to blood transfusion. The development of technologies including colloidal gold immunity and biochips has facilitated the shift from large-scale laboratory equipment to portable testing for pre-transfusion screening. Further, the introduction of artificial intelligence technologies such as machine learning, biometric technology, and computer vision has contributed to the advancement of intelligent pre-transfusion testing. This article reviews the various application scenarios, benefits, and drawbacks of different pre-transfusion detection technologies, analyzes the application of a series of new technologies in pre-transfusion detection and its future development trend, and provides a reference for promoting the development of pre-transfusion detection and even rapid disease marker detection.

Development and evaluation of a rapid and sensitive POC chemiluminescent assay for β-human chorionic gonadotropin / 中国免疫学杂志

Objective:To develop and evaluate a rapid and sensitive point-of-care chemiluminescent assay(POC-CLIA)for β-human chorionic gonadotropin(β-HCG).Methods:POC-CLIA was constructed based on alkaline phosphatase(Alp)-AMPPD lumi-nescence system and magnetic particles(Mps)carrier.Performance of POC-CLIA,including sensitivity,precision,accuracy,linear dilution,specificity,stability,hook effect and clinical application were evaluated.Results:Detection limit of β-HCG was 0.71 mU/ml,linear detection range was 0.710～1.092×104 mU/ml,and was no hook effect up to 1.7×105 mU/ml.Intra and inter batch coefficients of variation were less than 10％,and could be stored stably at 37℃ for 10 days.Accuracy deviation was within±10％,so results were reliable.There was no cross-reactivity between interfering substances and anti-β-HCG antibdies.For detecting β-HCG in 100 clinical serum samples,results were highly correlated with those that were tested by clinical standard methods(R2=0.997 0).Turnaround time for single sample was less than 15 min and throughput could reach 200 T/h.Conclusion:This method is adequate that can be widely used in grassroots communities to help large-scale screening of pregnancy and related diseases.

Thoracic ultrasound: a review of the state-of-the-art

ABSTRACT Thoracic ultrasound (TUS) is a tool that has become increasingly essential in the daily practice of thoracic medicine. Driven by the need to assess patients during the COVID-19 pandemic, there has been an increase in the use of point-of-care TUS, which has demonstrated several benefits, either as a complement to clinical decision-making for diagnosis or as a real-time guide for procedures, whether as a predictor or measure of treatment response. Here, we present a review of TUS, based on the most recent scientific evidence, from equipment and techniques to the fundamentals of pulmonary ultrasound, describing normal and pathological findings, as well as focusing on the management of lung disease and guidance for invasive thoracic procedures at the bedside. Finally, we highlight areas of perspective and potential lines of research to maintain interest in this valuable tool, in order to improve the diagnostic process and expand the treatment arsenal.

CRISPR-based molecular diagnostics: a review / 生物工程学报

Rapid and accurate detection technologies are crucial for disease prevention and control. In particular, the COVID-19 pandemic has posed a great threat to our society, highlighting the importance of rapid and highly sensitive detection techniques. In recent years, CRISPR/Cas-based gene editing technique has brought revolutionary advances in biotechnology. Due to its fast, accurate, sensitive, and cost-effective characteristics, the CRISPR-based nucleic acid detection technology is revolutionizing molecular diagnosis. CRISPR-based diagnostics has been applied in many fields, such as detection of infectious diseases, genetic diseases, cancer mutation, and food safety. This review summarized the advances in CRISPR-based nucleic acid detection systems and its applications. Perspectives on intelligent diagnostics with CRISPR-based nucleic acid detection and artificial intelligence were also provided.

Application of cell-free transcription and translation system in CRISPR technologies and the associated biosensors / 生物工程学报

Cell-free transcription and translation (TXTL) system is a cell extract-based system for rapid in vitro protein expression. The system bypasses routine laboratory processes such as bacterial transformation, clonal screening and cell lysis, which allows more precise and convenient control of reaction substrates, reduces the impact of bacteria on protein production, and provides a high degree of versatility and flexibility. In recent years, TXTL has been widely used as an emerging platform in clusterd regularly interspaced short palindromic repeat (CRISPR) technologies, enabling more rapid and convenient characterization of CRISPR/Cas systems, including screening highly specific gRNAs as well as anti-CRISPR proteins. Furthermore, TXTL-based CRISPR biosensors combined with biological materials and gene circuits are able to detect pathogens through validation of related antibiotics and nucleic acid-based markers, respectively. The reagents can be freeze-dried to improve portability and achieve point-of-care testing with high sensitivity. In addition, combinations of the sensor with programmable circuit elements and other technologies provide a non-biological alternative to whole-cell biosensors, which can improve biosafety and accelerate its application for approval. Here, this review discusses the TXTL-based characterization of CRISPR and their applications in biosensors, to facilitate the development of TXTL-based CRISPR/Cas systems in biosensors.

Research progress on multiplexed point-of-care testing technology for the diagnosis of infectious diseases / 中华检验医学杂志

Accurate and rapid diagnosis of infectious diseases can effectively prevent their spread and promptly curb the epidemic hazards. Multiplexed point-of-care testing (x-POCT) technology can effectively avoid misdiagnosis caused by the detection of one single target and achieve rapid screening and timely control of multiple infectious diseases. Research progress and the latest applications of x-POCT including x-POCT assay methods for different targets in the diagnosis of infectious diseases and their pathogens are summarized in this review. The paper-based, microfluidic chip-based, and microdroplet-based device platforms of x-POCT, and eventually the challenges and future perspectives of x-POCT, especially progress on the effective infectious disease surveillance network establishment under One Health concept are highlighted.

Emerging molecular diagnostic technologies for point-of-care testing: applications and prospects / 中华检验医学杂志

Molecular diagnostic technologies are critical diagnostic tools in clinical research. Point-of-care testing (POCT) presents numerous advantages such as portability, rapidity, accuracy, and cost-effectiveness, facilitating timely identification of infection sources and control of infectious disease transmission. This article explores the emerging molecular diagnostic technologies that can be used for POCT, including digital loop-mediated isothermal amplification technology and the clustered regularly interspaced short palindromic repeats and CRISPR-associated proteins system, while also discussing their future prospects.

Personal glucose meters coupled with signal amplification technologies for quantitative detection of non-glucose targets:Recent progress and challenges in food safety hazards analysis / 药物分析学报

Ensuring food safety is paramount worldwide.Developing effective detection methods to ensure food safety can be challenging owing to trace hazards,long detection time,and resource-poor sites,in addition to the matrix effects of food.Personal glucose meter(PGM),a classic point-of-care testing device,possesses unique application advantages,demonstrating promise in food safety.Currently,many studies have used PGM-based biosensors and signal amplification technologies to achieve sensitive and specific detection of food hazards.Signal amplification technologies have the potential to greatly improve the analytical performance and integration of PGMs with biosensors,which is crucial for solving the challenges associated with the use of PGMs for food safety analysis.This review introduces the basic detection principle of a PGM-based sensing strategy,which consists of three key factors:target recog-nition,signal transduction,and signal output.Representative studies of existing PGM-based sensing strategies combined with various signal amplification technologies(nanomaterial-loaded multienzyme labeling,nucleic acid reaction,DNAzyme catalysis,responsive nanomaterial encapsulation,and others)in the field of food safety detection are reviewed.Future perspectives and potential opportunities and challenges associated with PGMs in the field of food safety are discussed.Despite the need for complex sample preparation and the lack of standardization in the field,using PGMs in combination with signal amplification technology shows promise as a rapid and cost-effective method for food safety hazard analysis.

Efficacy analysis of anti-platelet in the treatment of high-risk non-disabling ischemic cerebrovascular events guided by point-of-care testing of CYP2C19 gene / 中华神经科杂志

Objective:To explore the efficacy and safety of different anti-platelet regimens in the treatment of high-risk non-disabling ischemic cerebrovascular events (HR-NICE) guided by point-of-care testing of CYP2C19 gene. Methods:A single-centre, prospective, randomised, open-label, and blinded endpoint design was uesd in the study. From July 2020 to January 2022, HR-NICE patients were enrolled in the Stroke Green Channel and Department of Neurology of Xuzhou Central Hospital, and all patients were scraped the buccal mucosa for screening for CYP2C19 loss-of-function allele carriers by point-of-care testing . Patients with intermediate metabolism were defined as those who carried 1 loss-of-function allele and patients with poor metabolism were those who carried 2 loss-of-function alleles. This study reduced the test turnaround time to 1 hour by using a fully automated medical polymerase chain reaction analyzer for a point-of-care test of CYP2C19 genotype. CYP2C19 loss-of-function allele carriers were divided according to the random number table method into the conventional treatment group (clopidogrel 75 mg, once a day), the ticagrelor group (ticagrelor 90 mg, twice a day) and the intensive dose group (clopidogrel 150 mg, once a day) separately combined with aspirin (100 mg, once a day) dual antiplatelet for 21 days. Baseline information, Acute Stroke Org 10172 Treatment Trial staging, 90-day modified Rankin Scale score, occurrence of adverse events and severe adverse events were collected for all the 3 groups. The primary efficacy outcome was new stroke within 90 days, and the primary safety outcome was severe or moderate bleeding within 90 days. Results:A total of 716 patients were included: 240 in the conventional treatment group, 240 in the ticagrelor group and 236 in the intensive dose group. There was no statistically significant difference between the 3 groups at baseline (all P>0.05). There were 26 cases (10.8%) with new stroke events in the conventional treatment group, 11 cases (4.6%) in the ticagrelor group and 4 cases (1.7%) in the intensive dose group, with statistically significant differences among the 3 groups (χ 2=19.28, P<0.05), and the differences between the conventional treatment group and the ticagrelor group (χ 2=6.59, P=0.010) and between the conventional treatment group and the intensive dose group (χ 2=16.83, P<0.001) were statistically significant, whereas the difference between the ticagrelor group and the intensive dose group was not statistically significant ( P>0.05). In the 3 groups, there was 1 case (0.4%) of severe bleeding in the conventional treatment group, 6 cases (2.5%) in the ticagrelor group and none in the intensive dose group, which showed statistically significant differences (χ 2=7.23, P<0.05), and there was statistically significant difference between the ticagrelor group and the intensive dose group ( P=0.030). Among the patients with intermediate CYP2C19 metabolism, there were 13 cases (13/158, 8.2%) with 90-day recurrent stroke in the conventional treatment group, 4 cases (4/153, 2.6%) in the ticagrelor group, and 0 case (0/159) in the intensive dose group, with statistically significant difference (χ 2=16.04, P<0.001), and the differences between the intensive dose group and the conventional treatment group were statistically significant (χ 2=13.64, P<0.001), whereas there was no statistically significant difference between the intensive dose group and the ticagrelor group ( P>0.05). In the patients with 90-day recurrent stroke in the intensive dose group, there was 0 case (0/159) with intermediate metabolism and 4 cases (4/77,5.2%) with poor metabolism, with statistically significant differences ( P=0.011), whereas there were no statistically significant differences in the conventional treatment group and the ticagrelor group ( P>0.05). Conclusions:Screening carriers of CYP2C19 loss-of-function alleles by point-of-care testing can quickly and precisely guide the treatment of patients with non-cardiogenic HR-NICE. An intensive clopidogrel dose of 150 mg, once a day combined with aspirin was effective in reducing stroke recurrence with less occurrence of any bleeding and adverse events, and patients with intermediate CYP2C19 metabolism may be the best population to benefit.

Point-of-care testing technology and experimental diagnosis of insect-borne diseases: applications and challenges / 中华检验医学杂志

Insect-borne infections are causing serious public health concerns worldwide. Point-of-care testing technology for insect-borne diseases can rapidly and accurately determine the pathogens, thus it plays an important role in the application of portable disease control measurements. This article provides an overview of the point-of-care testing technology for insect-borne infectious diseases regarding its application, advantages and limitations in experimental diagnoses, and its future trends.

Development of lateral flow immunoassay for SARS-CoV-2 antigen detection / 中国胸心血管外科临床杂志

@#This article summarizes the development of lateral flow immunoassay for SARS-CoV-2 antigen detection. Lateral flow immunoassay is a rapid, low cost, and ease of use detection tool that has been widely applied in clinical and public health sectors. Since the outbreak of COVID-19, the technique has been adopted for rapid antigen diagnostic test of SARS-CoV-2, including commonly used colloidal gold nanoparticle-based lateral flow immunoassays as well as various fluorescence-based lateral flow immunoassays. With innovations in labelling methods, this detection technique has been in continuous development and is shifting from qualitative toward quantitative as well as gaining sensitivity.

Rapid detection of Salmonella by enzymatic recombinase amplification combined with lateral flow chromatography / 预防医学

Objective@#To establish a rapid detection method for Salmonella based on the combination of enzymatic recombinase amplification (ERA) and lateral flow chromatography (LF), so as to provide technical support for the on-site detection of Salmonella.@*Methods@#Specific ERA primers and probes were designed based on the highly conserved flagella gene fimY in Salmonella. The primers were screened using capillary electrophoresis, and the probes were designed according to the amplification range of the screened primers. The amplification temperature and time were optimized to establish the amplification method, and the product was detected using LF strips. A standard strain of Salmonella was used to verify the sensitivity, 10 other gut bacteria were used to to verify the specificity and sensitivity, and the nucleic acid of the actual Salmonella strains was amplified to verify the detectability.@*Results@#After screening for Salmonella-specific primers using capillary electrophoresis, the minimum detection concentration was 5 copies/μL under the amplification temperature of 37 ℃ and reaction time of 20 minutes. This method had a positive amplification result for Salmonella nucleic acid, and the amplification results of 10 other gut bacteria were all negative, with good specificity.@*Conclusion@#This method provides a possibility for on-site point of care testing of Salmonella infection.

Efficacy of Different Doses of Clopidogrel in Combination with Aspirin in Patients with HR-NICE by Point-of-care Testing of CYP2C19 Gene / 医学研究杂志

Objective To investigate the efficacy of different doses of clopidogrel combined with aspirin in the treatment of high-risk non-disabling ischaemic cerebrovascular events(HR-NICE)under the precise guidance of point-of-care testing(POCT)of cy-tochrome P-450 2C19(CYP2C19)genotype.Methods The single-center,randomised,prospective,and blinded endpoint assess-ment was used.HR-NICE patients continuously enrolled in the stroke green channel and neurology ward of Xuzhou Central Hospital from January 2021 to January 2022,and all patients scraping of the buccal mucosa will be screened for CYP2C19 loss-of-function allele car-riers by POCT.According to the random number table method,they were divided into the intensive group(clopidogrel 150mg/d)and the conventional group(clopidogrel 75mg/d)combined with aspirin(100mg/d)dual antiplatelet for 21 days.Baseline information,acute stroke Org 10172 treatment trial(TOAST)staging and 90 days modified Rankin scale(mRS)score and occurrence of adverse events and severe adverse events were collected for the two groups.The primary efficacy outcome was new stroke within 90 days and the primary safety outcome was severe or moderate bleeding within 90 days.Results A total of 1301 patients were screened,of which 727 patients carried CYP2C19 loss-of-function allele,and 476 patients were included:236 patients in the intensive group and 240 patients in the conven-tional group.The differences between the two groups were not statistically significant at baseline(P>0.05);4 cases(1.7%)inthein-tensive group and 26 cases(10.8%)in the conventional group had a new stroke at 90 days.The differences between the two groups were statistically significant(χ2 = 16.827,P<0.001);0 case(0)in the intensive group and1 case(2.5%)in the conventional group had moderate to severe haemorrhage at 90 days.The differences between the two groups was not statistically significant(P>0.05).Conclu-sion In HR-NICE patients with CYP2C19 loss-of-function allele,the enhanced clopidogrel dose was more effective than the conven-tional dose in the treatment with the antiplatelet drug aspirin combined with clopidogrel,and had a consistent safety profile with no more adverse events such as bleeding.

Sensitivity and specificity of a syphilis rapid diagnostic test in blood donors' samples

Abstract Rapid Diagnostic Tests (RDT) are useful to identify syphilis cases, particularly for hard-to-reach populations and if laboratory services are scarce. However, RDT performance may be suboptimal. We aimed to assess the sensitivity and specificity of a syphilis RDT using well-characterized blood donors' samples. We categorized samples from 811 blood donors into five groups: 1 - Samples with reactive Chemiluminescence (QML), FTA-Abs, and VDRL; 2 - Samples with reactive QML and FTA-Abs, and nonreactive VDRL; 3 - Samples with reactive QML, and nonreactive for other markers (false-positives); 4 - Controls with nonreactive QML; and 5 - Samples reactive for HIV, with nonreactive QML. Sensitivity was tested in groups 1 (overall and according to VDRL titers) and 2; specificity was tested in groups 3‒5. The RDT had high specificity, even in samples reactive for HIV. The sensitivity was high (91.9%) in samples with reactive VDRL but varied between 75.0%‒100% according to VDRL titers. The overall sensitivity was lower (81.3%) in samples with reactive FTA-Abs and nonreactive VDRL. The RDT is a useful tool to detect active syphilis but may be more limited for cases with very early or remote infection, or those with prior treatment. When higher sensitivity is needed, additional strategies including recurrent testing or laboratory-based tests may be required.

Primary assessment of patients admitted to the emergency ward using arterial blood gas

Background: Arterial blood gas study (ABG) is a point-of-care testing (POCT) diagnostic tool that can furnish metabolic and respiratory aberrations. This study was conducted systematically, to assess the metabolic and respiratory aberrations quickly and the scope for corrective treatment so that metabolic and respiratory abnormalities get corrected. Materials and Methods: A prospective cross-sectional study was done among 150 cases admitted to the Department of Emergency Medicine during a three-month period where the study on ABG was done. Data was collected in the prescribed format and a stepwise interpretation of the ABG was done. The four primary disorders taken into consideration are metabolic acidosis, metabolic alkalosis, respiratory alkalosis, and respiratory acidosis Results: Out of 150 cases 82 had respiratory alkalosis, 51 had metabolic acidosis, ten had respiratory acidosis, and seven had metabolic alkalosis as a primary disorder. Conclusion: ABG analysis is a POCT diagnostic tool for analyzing various metabolic and respiratory aberrations and can also guide us in the scope for correction of the disorder.

Validación clínica de la prueba RT-LAMP para el diagnóstico rápido del SARS-CoV-2 / Clinical validation of the isothermal RT-LAMP test for rapid diagnosis of SARS-CoV-2

Introducción. Desde el primer reporte en la provincia de Wuhan (China) en el año 2019, el SARS-CoV-2 se ha diseminado por todo el mundo, provocando un enorme impacto en la salud pública. Para su diagnóstico, la Organización Mundial de la Salud ha incentivado el desarrollo de pruebas rápidas, de simple ejecución, sensibles y específicas, que complementan la RT-qPCR como prueba de referencia. La prueba RT-LAMP ha mostrado ser una excelente alternativa para la detección del SARS-CoV-2 en diferentes biofluidos. Objetivo. Validar la técnica RT-LAMP colorimétrica en muestras de hisopado nasofaríngeo previamente confirmadas por RT-qPCR, usando el protocolo Charité, Berlín, Alemania. Materiales y métodos. Un total de 153 muestras de hisopado nasofaríngeo de individuos con sospecha de COVID-19 se sometieron a RT-qPCR y RT-LAMP, usando un estuche comercial colorimétrico (NEB, Germany). La RT-LAMP se practicó con las muestras de ARN extraídas del hisopado nasofaríngeo y con muestras crudas sin previa extracción de ARN. El resultado fue evaluado por un simple cambio de color en la reacción. Resultados. La sensibilidad y especificidad de la técnica RT-LAMP para detectar el gen N del SARS-CoV-2 mediante un set de cebadores previamente reportados (set de Broughton), arrojó valores de 0,97 (0,85-1,00) y 0,81 (0,65-0,92), respectivamente, con un intervalo de confianza del 95%. Otro set de cebadores dirigidos contra otra región del mismo gen (set de Lalli) arrojó valores de sensibilidad y especificidad de 0,96 (0,78-1,00) y 0,77 (0,55-0,92), respectivamente. Sin previa extracción de ARN, se encontró que la sensibilidad fue del 0,95 (0,74-1,00) y la especificidad del 0,88 (0,64-0,99). Conclusiones. Estos resultados evidencian que la técnica RT-LAMP podría considerarse una prueba diagnóstica rápida, de fácil ejecución, libre de equipos sofisticados, sensible y específica, para el diagnóstico del SARS-CoV-2 en muestras de hisopados nasofaríngeos.

Introduction: Since the first report in Wuhan (China) in 2019, the SARS-CoV-2 virus has spread throughout the world, with a significant impact in public health. To contain its transmission, the WHO has encouraged the development of rapid, simple, sensitive and specific tests that complement qRT-PCR, as the gold standard. RT-LAMP has shown to be a good alternative to detect SARS-CoV-2 in different fluid samples. Objective: To validate the colorimetric RT-LAMP technique using two sets of primers targeting N gene of SARS-CoV-2 in 117 nasopharyngeal swab samples previously confirmed by RT-qPCR, using the Charité/Berlin protocol. Material and methods: A total of 153 nasopharyngeal swab samples from individuals with suspected COVID-19 were subjected to qRT-PCR and RT-LAMP using a commercial colorimetric kit (NEB, Germany). RT-LAMP was performed using both extracted RNA samples and raw samples without prior RNA extraction, and the result was assessed by a simple color change in the reaction. Results: Sensitivity and specificity for the previously reported RT-LAMP primers (Broughton set) targeting N gene of SARS-CoV-2 were 0.97 (0.85-1.00) and 0.81 (0.65-0.92) respectively, with CI95%. The Lalli primers targeting another region of the N gene used showed a sensitivity value of 0.96 (0.78-1.00) and a specificity of 0.77 (0.55-0.92). Without RNA extraction we found a sensitivity value of 0.95 (0.74, 1.00) and a specificity of 0.88 (0.64, 0.99). A sensitivity value of 0.95 (0.74-1.00) and a specificity 0.88 (0.64-0.99) were found without prior RNA extraction. Conclusion: Taking together, the results showed that RT-LAMP technique could be considered as a rapid diagnostic test, easy to perform, free of sophisticated equipment, sensitive and specific to diagnose SARS-CoV-2 in nasopharyngeal swabs with and without prior RNA extraction, allowing its implementation in places with scarce resources.

Amplificación directa de ADN de Bordetella pertussis purificado de hisopados nasofaríngeos por un método de bajo costo, rápido (60-segundos) y libre de equipos / Direct amplification of Bordetella pertussis DNA purified from nasopharyngeal swabs by a low-cost, fast (60-second), and equipment-free method

RESUMEN Objetivo. Desarrollar y evaluar un método de bajo costo basado en celulosa para la purificación rápida y amplificación directa de ADN de Bordetella pertussis de hisopados nasofaríngeos. Materiales y métodos. Se prepararon discos de celulosa y se evaluaron diferentes parámetros (buffers de lisis/lavado, número de discos y elución de ADN). El método se acopló a una amplificación directa por PCR en tiempo real (qPCR) y se estimó el rendimiento utilizando hisopados nasofaríngeos que fueron positivos (n=100) y negativos (n=50) para ADN B. pertussis por qPCR, comparado con el método basado en columnas de sílice. Se calculó el grado de concordancia, sensibilidad, especificidad, valor predictivo positivo (VPP) y valor predictivo negativo (VPN). Se evaluó la factibilidad del método rápido para ser acoplado a un ensayo colorimétrico de amplificación isotérmica mediada por lazo (LAMP). Resultados. El método rápido con un disco de celulosa y buffer de lisis y lavado conteniendo PVP-40 y Tween 20, respectivamente, mostró una mayor capacidad para purificar ADN amplificable de B. pertussis. El método tuvo una sensibilidad de 89,0% (IC95%, 80,2%-94,9%) y una especificidad de 98,5% (IC95%, 92,1%-100,0%), con un buen grado de concordancia (Kappa=0,867; IC95% 0,788 - 0,946), respecto al método referencial. Los VPP y VPN fueron 98,6% (IC95%, 92,7,2%-100,0%) y 88,2% (IC95%, 78,7%-94,4%), respectivamente. Se evidenció una amplificación exitosa por LAMP, y se obtuvieron resultados comparables con el método por columnas de sílice. Conclusión. El método desarrollado es simple, de bajo costo y libre de equipos para la obtención rápida (60 segundos) de ADN en el punto de atención, y puede ser implementado en diversas técnicas moleculares orientados al diagnóstico oportuno y al estudio epidemiológico de tos ferina.

ABSTRACT Objective. To develop and evaluate a low-cost cellulose-based method for rapid purification and direct amplification of Bordetella pertussis DNA from nasopharyngeal swabs. Materials and methods. We prepared cellulose discs and evaluated different parameters (lysis/wash buffers, number of discs and DNA elution). The method was coupled to a direct real-time PCR (qPCR) amplification and the performance was estimated using nasopharyngeal swabs that were positive (n=100) and negative (n=50) for B. pertussis DNA by qPCR, compared to the silica column-based method. We calculated sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) and the degree of agreement. The feasibility of the rapid method to be coupled to a loop-mediated isothermal amplification colorimetric assay (LAMP) was evaluated. Results. The rapid method, with a cellulose disk and lysis and wash buffer containing PVP-40 and Tween 20, respectively, showed a greater capacity to purify amplifiable DNA from B. pertussis. The method had a sensitivity of 89.0% (95%CI: 80.2%-94.9%) and a specificity of 98.5% (95%CI: 92.1%-100.0%), with a good degree of agreement (Kappa=0.867; 95%CI: 0.788 - 0.946), compared to the reference method. The PPV and NPV were 98.6% (95%CI: 92.7.2%-100.0%) and 88.2% (95%CI: 78.7%-94.4%), respectively. Successful amplification by LAMP was evident, and comparable results were obtained with the silica column method. Conclusion. The developed method is simple, low-cost and equipment-free for rapid (60 seconds) DNA collection at the point of care, and can be implemented in various molecular techniques aimed at the timely diagnosis and epidemiological study of pertussis.

Low performance of a SARS-CoV-2 point-of-care lateral flow immunoassay in symptomatic children during the pandemic

Abstract Objective: to evaluate the accuracy of an antibody point-of-care lateral flow immunoassay (LFI -Wondfo Biotech Co., Guangzhou, China) in a pediatric population. Methods: children and adolescents (2 months to 18 years) with signs and symptoms suggestive of acute SARS-CoV-2 infection were prospectively investigated with nasopharyngeal RT-PCR and LFI at the emergency room. RT-PCR was performed at baseline, and LFI at the same time or scheduled for those with less than 7 days of the clinical picture. Overall accuracy, sensitivity and specificity were assessed, as well as according to the onset of symptoms (7-13 or ≥14 days) at the time of the LFI test. Results: In 175 children included, RT-PCR and LFI were positive in 51 (29.14%) and 36 (20.57%), respectively. The overall sensitivity, specificity, positive and negative predictive value was 70.6% (95%CI 56.2-82.5), 96.8% (95%CI 91.9-99.1), 90.0% (95%CI 77.2-96.0), and 88.9% (95%CI 83.9-92.5), respectively. At 7-13 and ≥14 days after the onset of symptoms, sensitivity was 60.0% (95%CI 26.2-87.8) and 73.2% (95%CI 57.1-85.8) and specificity was 97.9% (95%CI 88.7-99.9) and 96.1% (95%CI 89.0-99.2), respectively. Conclusion: Despite its high specificity, in the present study the sensitivity of LFI in children was lower (around 70%) than most reports in adults. Although a positive result is informative, a negative LFI test cannot rule out COVID-19 in children.