Comparison of three molecular diagnostic assays for SARS-CoV-2 detection: Evaluation of analytical sensitivity and clinical performance.

BACKGROUND: Currently, SARS-CoV-2 RNA detection using real-time reverse-transcription PCR (rRT-PCR) is the standard diagnostic test for COVID-19 infection. Various rRT-PCR assays are currently used worldwide, targeting different genes of the SARS-CoV-2. Here, we compared the analytical sensitivity and clinical performance (sensitivity and specificity) of Allplex SARS-CoV-2/FluA/FluB/RSV assay (Seegene), Standard M nCoV real-time detection kit (SD Biosensor), and U-TOP COVID-19 detection kit (Seasun Biomaterials) for SARS-CoV-2 detection. METHODS: Two hundred and forty-nine nasopharyngeal swab samples were evaluated to compare the clinical performance of the rRT-PCR assays. For the analytical performance evaluation, two RNA controls with known viral loads-SARS-CoV-2 RNA control and SARS-COV-2 B.1.351 RNA control-were used to investigate the potential impact of SARS-CoV-2 variants, particularly the B.1.351 lineage. RESULTS: Limits of detection ranged from 650 to 1300 copies/ml for rRT-PCR assays, and the mean differences in cycle threshold (Ct ) values of the two RNA controls were within 1.0 for each target in the rRT-PCR assays (0.05-0.73), without any prominent Ct value shift or dropouts in the SARS-COV-2 B.1.351 RNA control. Using the consensus criterion as the reference standard, 89 samples were positive, whereas 160 were negative. The overall clinical performance of rRT-PCR assays was comparable (sensitivity 98.88%-100%; specificity 99.38%-100%), whereas the sensitivities of each target gene were more variable. CONCLUSIONS: The three rRT-PCR assays showed comparable analytical sensitivity and clinical performance. The analytical and clinical sensitivities of each target gene were influenced more by the primer and probe design than the target gene itself.

Factors influencing the performance of rapid SARS-CoV-2 antigen tests under field condition.

BACKGROUND: Globally, real-time reverse transcription-polymerase chain reaction (rRT-PCR) is the reference detection technique for SARS-CoV-2, which is expensive, time consuming, and requires trained laboratory personnel. Thus, a cost-effective, rapid antigen test is urgently needed. This study evaluated the performance of the rapid antigen tests (RATs) for SARS-CoV-2 compared with rRT-PCR, considering different influencing factors. METHODS: We enrolled a total of 214 symptomatic individuals with known COVID-19 status using rRT-PCR. We collected and tested paired nasopharyngeal (NP) and nasal swab (NS) specimens (collected from same individual) using rRT-PCR and RATs (InTec and SD Biosensor). We assessed the performance of RATs considering specimen types, viral load, the onset of symptoms, and presenting symptoms. RESULTS: We included 214 paired specimens (112 NP and 100 NS SARS-CoV-2 rRT-PCR positive) to the analysis. For NP specimens, the average sensitivity, specificity, and accuracy of the RATs were 87.5%, 98.6%, and 92.8%, respectively, when compared with rRT-PCR. While for NS, the overall kit performance was slightly lower than that of NP (sensitivity 79.0%, specificity 96.1%, and accuracy 88.3%). We observed a progressive decline in the performance of RATs with increased Ct values (decreased viral load). Moreover, the RAT sensitivity using NP specimens decreased over the time of the onset of symptoms. CONCLUSION: The RATs showed strong performance under field conditions and fulfilled the minimum performance limit for rapid antigen detection kits recommended by World Health Organization. The best performance of the RATs can be achieved within the first week of the onset of symptoms with high viral load.

Wide Variability in the Sensitivity and Specificity of Rotavirus Immunoassay Diagnostic Kits in Practice.

INTRODUCTION: Most hospitals rely on rapid antigen-detection kits for the diagnosis of rotavirus infection. Several small studies reviewed the sensitivity and specificity of some of these kits. These studies showed discrepancy in results obtained for sensitivity and specificity that varied according to the type of kit used, area of study, and type of test used as standard for diagnosis of rotavirus infection. The objective of the study is to determine the sensitivity and specificity of five commonly used rotavirus immunoassay kits in comparison to RT-PCR as standard. METHODOLOGY: Stool samples (N = 1,414) collected from children under 5 years of age hospitalized with gastroenteritis were tested for rotavirus by immunoassay kits and RT-PCR in a prospective hospital-based surveillance study conducted at 7 centers in Lebanon. Concordance and discrepancy between the two methods was used to calculate sensitivity and specificity, using RT-PCR as the "gold standard". RESULTS: The sensitivity and specificity were respectively 95.08% and 86.62% for the SD Bioline® (Standard Diagnostics, Inc, South Korea) kit calculated on 645 samples, 65.86% and 45.90% for the VIROTECT® (Trinity Biotech, Ireland) kit calculated on 327 samples, 83.9% and 64.2% for the Rota-Strip (C-1001) (Coris Bioconcept, Belgium) calculated on 95 samples, 52.3% and 10.9% for the Acon® (Acon Laboratories, Inc, California, USA) kit calculated on 122 samples, 68.1% and 20% for the VIKIA® Rota-Adéno (Biomerieux, France) kit calculated on 32 samples. CONCLUSION: A wide discrepancy was detected between the calculated and advertised sensitivity and specificity for most of the kits.

Comparison of four commercially available point-of-care tests to detect antibodies against canine distemper virus in dogs.

Pre-vaccination antibody testing to determine dogs' immunity against canine distemper virus (CDV) is increasingly used. Four point-of-care tests (POC A-D) are available in Europe, but their diagnostic accuracy has not been compared. The study evaluated the diagnostic accuracy and usability of these tests. Sera of client-owned dogs (n = 198; healthy n = 22; unhealthy dogs n = 176) and specific pathogen-free (SPF) dogs (n = 40) were included. Virus neutralisation (VN) was performed as the reference standard. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and overall accuracy (OA) were determined. McNemar's test was used to determine significant differences between specificity and sensitivity of the tests and Cohen's kappa was used to assess agreement. The prevalence of anti-CDV antibodies by VN was 80% in client-owned dogs overall, with 100% prevalence in healthy dogs, and 0% in SPF dogs. POC-C and POC-D were considered easiest to perform. Specificity of all tests was high using sera from SPF dogs (88-100%). In healthy dogs, sensitivity was variable (45-98%). Specificity was low in all four POC tests when using sera from acutely ill dogs (6-53%) and clinically healthy dogs with chronic disease (5-77%). In client-owned dogs, including healthy and unhealthy dogs, agreement was poor between tests. All POC tests had a low specificity when investigating sera from ill client-owned dogs and usefullness of these tests especially in dogs that are acutely ill or have chronic disease is not supported by this study.

Performance of the Influ a + B K-SeT® assay as compared to two RT-PCR assays for detection of influenza virus.

OBJECTIVES: To evaluate the performance of Influ A + B K-SeT®, a rapid influenza antigen detection kit, in order to determine whether its implementation as a point-of-care test in the emergency room (ER) is justified. METHODS: Nasopharyngeal swabs (n = 170) were collected in triplicates from patients with suspected influenza infection. One sample was tested by the Influ A + B K-SeT® kit and the other two samples were analyzed with Simplexa™ Flu A/B & RSV Direct Kit and Xpert® Flu, two RT-PCR-based assays routinely used in the ER. RESULTS: The sensitivity and specificity of the Influ A + B K-SeT® kit were 91.2%-94.5% and 98.2%, respectively, compared to the Xpert® Flu assay and the Simplexa™ Flu A/B & RSV Direct Kit, respectively. CONCLUSIONS: Considering the satisfactory diagnostic performance of the Influ A + B K-SeT® test, its implementation as a point-of-care is expected to aid in decision-making, minimize time-to-result and reduce healthcare costs.

Usability assessment of seven HIV self-test devices conducted with lay-users in Johannesburg, South Africa.

INTRODUCTION: The first 90 of the 90-90-90 initiative introduced by the World Health Organization(WHO) in 2015 requires 90% of people with HIV be aware of their status by 2020. In South Africa, conventional facility-based testing had reached 84.9% in 2018; innovative new methods, like HIV self-testing(HIVST) may close the testing gap. This study aimed to determine the usability of seven HIVST kits among untrained South Africans. METHODS: This cross-sectional study of 1400 adults in Johannesburg evaluated the usability of five blood fingerstick and two oral fluid HIVSTs, using WHO prequalification criteria, from June 2016 to June 2018. Participants were handed one kit, with no further information about the device or test procedure, and asked to perform the test in front of an observer. The observer used product-specific semi-structured questionnaires organized into a composite usability index(UI) using a HIVST process checklist, a contrived results interpretation and a post-test interview that expanded on participant experiences with the device and instructions-of-use(IFU). Participants were not tested themselves, but provided with contrived results to interpret. RESULTS: The average UI was 92.8%(84.2%-97.6%); the major difficulty was obtaining and transferring the specimen. Participants correctly interpreted 96.1% of the non-reactive/negative, 97.0% of the reactive/positive, 98.0% of the invalid and 79.9% of the weak positive results. Almost all participants(97.0%) stated they would visit a clinic or seek treatment for positive results; with negative results, half(50.6%) stated they should re-test in the next three months while one-third(36.1%) said they should condomize. Nearly all found the devices easy to use(96.6%), the IFUSs easy to understand(97.9%) and felt confident using the test unassisted(95.9%) but suggested improvements to packaging/IFUs to further increase usability; 19.9% preferred clinic-based testing to HIVST. CONCLUSION: The UI and interpretation of results was high and in-line with previous usability studies, suggesting that these kits are appropriate for use in the general, untrained and unsupervised public.

Impact of Mycobacterium bovis-induced pathology on interpretation of QuantiFERON®-TB Gold assay results in African buffaloes (Syncerus caffer).

The cytokine interferon gamma-inducible protein 10 (IP-10) is a sensitive biomarker of Mycobacterium bovis (M. bovis) infection in African buffaloes (Syncerus caffer). However, elevated levels of IP-10 in QuantiFERON®-TB Gold (QFT) unstimulated whole blood compromises the utility of this biomarker. In this study, IP-10 and interferon gamma (IFN-γ) concentrations in whole blood samples from M. bovis culture-confirmed buffaloes with varying degrees of pathological changes (n = 72) and uninfected controls (n = 70) were measured in the IP-10 release assay (IPRA) and IFN-γ release assay (IGRA), respectively. Findings suggest that concentrations of both cytokines in QFT Nil tubes were higher in infected buffaloes with macroscopic pathological changes consistent with bovine tuberculosis compared to uninfected controls, and IGRA values increased with more severe pathological changes in infected buffaloes (p < 0.05). Finally, in culture-confirmed buffaloes with IPRA-negative and IGRA-positive test results, most animals were also those with the most advanced pathology. We conclude that IP-10 and IFN-γ concentrations measured in QFT Nil tubes may provide insight into the presence of M. bovis pathology in infected buffaloes. Furthermore, this study highlights the value in evaluating cytokine production in both antigen-stimulated and unstimulated samples when interpreting cytokine release assay results.

Comparative performance of four rapid Ebola antigen-detection lateral flow immunoassays during the 2014-2016 Ebola epidemic in West Africa.

BACKGROUND: Without an effective vaccine, as was the case early in the 2014-2016 Ebola Outbreak in West Africa, disease control depends entirely on interrupting transmission through early disease detection and prompt patient isolation. Lateral Flow Immunoassays (LFI) are a potential supplement to centralized reference laboratory testing for the early diagnosis of Ebola Virus Disease (EVD). The goal of this study was to assess the performance of commercially available simple and rapid antigen detection LFIs, submitted for review to the WHO via the Emergency Use Assessment and Listing procedure. The study was performed in an Ebola Treatment Centre laboratory involved in EVD testing in Sierra Leone. In light of the current Ebola outbreak in May 2018 in the Democratic Republic of Congo, which highlights the lack of clarity in the global health community about appropriate Ebola diagnostics, our findings are increasingly critical. METHODS: A cross-sectional study was conducted to assess comparative performance of four LFIs for detecting EVD. LFIs were assessed against the same 328 plasma samples and 100 whole EDTA blood samples, using the altona RealStar Filovirus Screen real-time RT-PCR as the bench mark assay. The performance of the Public Health England (PHE) in-house Zaire ebolavirus-specific real time RT-PCR Trombley assay was concurrently assessed. Statistical analysis using generalized estimating equations was conducted to compare LFI performance. FINDINGS: Sensitivity and specificity varied between the LFIs, with specificity found to be significantly higher for whole EDTA blood samples compared to plasma samples in at least 2 LFIs (P≤0.003). Using the altona RT-PCR assay as the bench mark, sensitivities on plasma samples ranged from 79.53% (101/127, 95% CI: 71.46-86.17%) for the DEDIATEST EBOLA (SD Biosensor) to 98.43% (125/127, 95% CI: 94.43-99.81%) for the One step Ebola test (Intec). Specificities ranged from 80.20% (158/197, 95% CI: 74.07-88.60%) for plasma samples using the ReEBOV Antigen test Kit (Corgenix) to 100.00% (98/98, 95% CI: 96.31-100.00%) for whole blood samples using the DEDIATEST EBOLA (SD Biosensor) and SD Ebola Zaire Ag (SD Biosensor). Results also showed the Trombley RT-PCR assay had a lower limit of detection than the altona assay, with some LFIs having higher sensitivity than the altona assay when the Trombley assay was the bench mark. INTERPRETATION: All of the tested EVD LFIs may be considered suitable for use in an outbreak situation (i.e. rule out testing in communities), although they had variable performance characteristics, with none possessing both high sensitivity and specificity. The non-commercial Trombley Zaire ebolavirus RT-PCR assay warrants further investigation, as it appeared more sensitive than the current gold standard, the altona Filovirus Screen RT-PCR assay.

A review of the atomoRapid HIV self-testing device: an acceptable and easy alternative to facilitate HIV testing.

Introduction:HIV testing is the gateway to both HIV prevention and treatment, and increased HIV testing and linkage to services is vital for an effective HIV response. HIV testing has progressed significantly from a lengthy laboratory process conducted by specialist medical staff to rapid point of care testing performed by trained lay staff. Despite HIV testing services being widely available, testing rates remain suboptimal among young people and men. Alternative delivery strategies that complement conventional testing services are needed to reach these priority groups. Areas covered:This article reviewed the AtomoRapid HIV self-testing (HIVST) device as an innovative alternative to conventional testing. Expert commentary:HIVST complements traditional HIV testing options and can be used to overcome major barriers to testing by catering for testing outside of conventional settings and by allowing individuals to test themselves privately, and at their own discretion and frequency. We conclude that the high sensitivity, specificity, acceptability, usability, and fidelity of this device makes it an appropriate option for the enhancement of HIV testing strategies for harder to reach populations, such as young people and men.

Rapid Diagnostic Tests in Childhood Infections.

Presumptive treatment of infections often results in irrational antimicrobial use resulting in detrimental spread of drug resistance and untoward side effects. A rapid diagnostic test (RDT) is a test that delivers a result earlier than conventional testing methods employed in the past to identify the offending microorganism. RDTs help in early definitive therapy, reduction in hospital stay and cost, and in degree of morbidity and mortality associated with the infection. To select a proper RDT, one should consider how specific and sensitive the test is. Most RDTs gives a qualitative result not quantitative; hence disease severity, monitoring of the disease, prognostication and therapeutic efficacy cannot be assessed. A RDT should be easy to perform, should not require sophisticated machines, and kits should be stable in extremes of temperature. RDTs may be of immense help in remote places where conventional diagnostic facilities are unavailable or lack quality. RDTs hold promise of reasonable diagnostic accuracy if done in a optimal clinical background. They should never be ordered as a shotgun approach to exclude all possible infections but should be used judiciously with appropriate interpretation.

Analytical performance of three diagnostic reagents for HBsAg on an automatic ELISA analyzer.

PURPOSE: We conducted performance tests of three HBsAg ELISA diagnostic reagents using an Addcare 600 (Yantai Addcare Bio-tech Limited Company) and studied the consistency between the qualitative results and chemiluminescent microparticle immunoassay (CMIA) results. METHODS: Diagnostic kits (ELISA) for HBsAg manufactured by INTEC ("A"), KHB ("B") and Wantai ("C") were tested on an Addcare 600 to evaluate their intermediate precision, repeatability, and C50. Furthermore, three ELISA detection systems and a quantitative test kit for HBsAg (Abbott) were employed to screen 1000 serum samples, while CMIA reactive samples were used to perform the confirmatory tests. The evaluation indexes of the ELISA reagent performances were calculated. RESULTS: The intermediate precision and repeatability of each system were <14% and <9%, respectively, while C50 was 0.105-0.115 IU/mL. The sensitivities of A, B, and C were 98.70%, 99.28%, and 99.13%, respectively, while their specificities were 98.06%, 99.03%, and 97.42%, respectively. The Youden indexes were 96.76%, 98.31%, and 96.55%, respectively, while the kappa values were 0.965 (P=.000), 0.981 (P=.000), and 0.967 (P=.000), respectively. CONCLUSION: The combination of Addcare 600 with the three reagents could meet the clinical requirement. Reagent B demonstrated the best performance. Although the results consistency among the three systems and CMIA was good, our findings suggest that ELISA should be combined with a confirmatory test to exclude false-positive and false-negative results caused by low HBsAg levels.

A retrospective analysis of the application of the Elecsys® HIV combi PT assay in southern China.

BACKGROUND: Fourth-generation HIV assays have been implemented worldwide as a screening test for many years. Understanding the performance of fourth-generation assay in low HIV prevalence region is pivotal to interpret the test result correctly. In this study, retrospective analysis was used to evaluate application of the Elecsys® HIV combi PT assay. METHODS: A total of 85 043 specimens from a low prevalence setting were detected between June 2013 and October 2015. We evaluated the false-positive rate (FPR), specificity, and positive predictive value (PPV). RESULTS: The specificity between male and female were 99.85% and 99.82%, respectively. The PPV on male (50.75%) was higher than female (17.05%) significantly, while the FPR was 0.15% and 0.18%. The gap between false-positive (median: 1.83, [IQR]: 1.30, 3.38) and confirmed-positive (median: 407.5, [IQR]: 184.2, 871.7) is enormous. The highest s/co ratio for false-positive cases was 85.45, while the lowest s/co ratio for confirmed-positive cases was 59.68. Various reasons were attributed to false-positive cases. CONCLUSION: Optimal cutoff value is needed to be set to reduce the false-positive cases and predict the final status of HIV infection reliably. Retrospective analysis will help us to understand more about diagnosis of HIV.

Comparison of the Roche Cobas® 4800 HPV assay to Roche Amplicor for detection of high-risk human papillomavirus.

UNLABELLED: Roche Amplicor HPV (AMP) had previously been used for detection of high-risk human papillomavirus (HR-HPV) in epidemiological and clinical studies. As this assay is no longer available, we compared its performance using PreservCyt samples from women aged of 18-24 years attending for routine cervical cytology screening to Roche Cobas® 4800 (Cobas) to determine if subsequent studies could continue using the Cobas assay. Overall 507 samples were tested on Cobas and compared to previous AMP results, with discrepant samples tested on Roche Linear Array. RESULTS: Overall, agreement between the Cobas and AMP for the presence of HR HPV types was very high (κ = 0.81) (95 % CI: 0.76 - 0.87) with percentage agreement of 91.57 %. Cobas is comparable to AMP for the detection of HR-HPV types in a community recruited cohort of healthy women.

[THE COMPARATIVE CHARACTERISTIC OF SETS OF REAGENTS FOR IDENTIFICATION OF ANTIGENS OF ROTAVIRUSES USED ON THE TERRITORY OF RUSSIA].

The study was carried out to evaluate and compare analytical characteristics of reagents kits for identification of antigens of rotaviruses SD BIOLINE Rotavirus (Standard Diagnostics, Korea), RIDA Quick Rotavirus (R-biopharm AG, Germany), RotaStick One-Step Test (Novamed Ltd., Israel), QuickStripe Rotavirus (Savyon doagnostics Ltd., Israel), Rotavirus-antigen-IFA-BEST (Vector-Best, the Russian Federation), Rota-antigen (NPP AKVAPAST, the Russian Federation). The panel included 84 positive and 43 negative samples of rotaviruses group A according their content. The reagents kit "Amplisense OKI screen-FL" with confirming [P]G typing of positive samples was used for comparison. The comparison of analytical sensitivity of reagents kits was implemented on panel characterized by using technique of droplet digital polymerase chain-reaction. The indicators of diagnostic sensitivity and specificity of reagents kits amounted to 84.52% and 100%for SD BIOLINE Rotavirus and RIDA Quick Rotavirus, 71.43% and 100% for RotaStick One-Step Test, 75.00% and 100%for QuickStripe Rotavirus, 83.33% and 100% for Rotavirus-antigen-FA-BEST, 83.33% and 100%for Rota-antigen. The analytical sensitivity of immunochromatographic and immunoenzyme kits amounted to 5 x 106 GE/ml for [P]8G4 genotype of rotaviruses of group A. The reagents kits SD BIOLINE Rotavirus, RIDA Quick Rotavirus and Rotavirus-antigen-IFA-BESTdemonstrated matched high indicators of diagnostic sensitivity and specificity sufficient for etiological diagnostic of rotavirus infection at acute stage of disease. The analytical sensitivity of compared kits does not allow recommending them to apply in analysis of samples characterized by lower concentrations of rotaviruses (asymptomatic agents, objects of environment).

[THE INTERPRETATION OF RESULTS OF DETECTION OF AGENTS OF VIRAL DIARRHEA IN REAL-TIME MODE].

The study was carried out to establish values of parameters characterizing concentrations of pathogens (threshold cycle - Ct) correlating with acute phase of viral gastroenteritis. The groups of patients with sporadic and group morbidity of acute intestinal infections were examined. The reagents kits Amplience (The central research institute of epidemiology, Russia), in real-time format polymerase chain reaction were applied to detect Rotavirus grA, Norovirus GII, Astrovirus, Adenovirus grF, Shigella spp, EIEC, Salmonella spp, Campylobacter spp (thermophilic group).The analysis was applied to distribution of Ct depending on isolated and combined detection ofpathogens in clinical samples. The evaluation was implemented concerning effect on Ct values of both inhibitors of polymerase chain reaction contained in feces and application of various amplifiers such as Rotor-Gene Q (QIAGEN, Germany), CFX96 (Bio-Rad, USA), "DT-96" (DNA technology, Russia). The risks of cross contamination during carrying out of investigations are evaluated. The asymmetric or bi-modal character of distribution of Ct values related to cases of combined detection of several pathogens is established. The following indicators are established common for patients with mono-infections (Ct mean ± SD): Rotavirus grA (Ct 20.63 ± 6.35; n = 978), Norovirus GII Astrovirus (Ct 21.06 ± 6.54; n = 54), Adenovirus grF (Ct 8.42 ± 2.4; n = 42). The corresponding values for victims of infective episodes amounted to Norovirus GII (24.19 ± 5.29; n = 447) and Rotavirus grA (18.65 ± 4.16; n = 50). The recommendations are presented concerning practical interpretation of results of real-time polymerase chain reaction. The indirect characteristic of content of pathogens in samples of clinical material derived from real-time polymerase chain reaction provides important information about association of pathogen with acute phase of disease. The high informativeness of given type of investigations support possibility of its effective implementation not only doing etiologic diagnostic but also in case of isolation of pathogen in clinically healthy individuals and examination of objects of environment.

Immuno-Chromatographic Wicking Assay for the Rapid Detection of Chikungunya Viral Antigens in Mosquitoes (Diptera: Culicidae).

The outbreak of disease caused by chikungunya virus (CHIKV) in 2006 and the recent spread of this virus to the Americas in 2013 indicate the potential for this virus to spread and cause significant disease. However, there are currently no accurate and reliable field-usable, diagnostic methods to provide critical, real-time information for early detection of CHIKV within the vector populations in order to implement appropriate vector control and personal protective measures. In this article, we report the ability of an immuno-chromatographic assay developed by VecTOR Test Systems Inc. to detect CHIKV in a pool of female Aedes mosquitoes containing a single CHIKV-infected mosquito. The CHIKV dipstick assay was simple to use, did not require a cold chain, and provided clear results within 1 h. It was highly specific and did not cross-react with samples spiked with a variety of other alpha, bunya, and flaviviruses. The CHIKV assay can provide real-time critical information on the presence of CHIKV in mosquitoes to public health personnel. Results from this assay will allow a rapid threat assessment and the focusing of vector control measures in high-risk areas.

Optical and analytical investigations on dengue virus rapid diagnostic test for IgM antibody detection.

Evaluation of binding between analytes and its relevant ligands on surface plasmon resonance (SPR) biosensor is of considerable importance for accurate determination and screening of an interference in immunosensors. Dengue virus serotype 2 was used as a case study in this investigation. This research work compares and interprets the results obtained from analytical analysis with the experimental ones. Both the theoretical calculations and experimental results are verified with one sample from each category of dengue serotypes 2 (low, mid, and high positive), which have been examined in the database of established laboratorial diagnosis. In order to perform this investigation, the SPR angle variations are calculated, analyzed, and then validated via experimental SPR angle variations. Accordingly, the error ratios of 5.35, 6.54, and 3.72% were obtained for the low-, mid-, and high-positive-specific immune globulins of patient serums, respectively. In addition, the magnetic fields of the biosensor are numerically simulated to show the effect of different binding mediums.

Multicountry prospective clinical evaluation of two enzyme-linked immunosorbent assays and two rapid diagnostic tests for diagnosing dengue fever.

We evaluated four dengue diagnostic devices from Alere, including the SD Bioline Dengue Duo (nonstructural [NS] 1 Ag and IgG/IgM), the Panbio Dengue Duo Cassette (IgM/IgG) rapid diagnostic tests (RDTs), and the Panbio dengue IgM and IgG capture enzyme-linked immunosorbent assays (ELISAs) in a prospective, controlled, multicenter study in Peru, Venezuela, Cambodia, and the United States, using samples from 1,021 febrile individuals. Archived, well-characterized samples from an additional 135 febrile individuals from Thailand were also used. Reference testing was performed on all samples using an algorithm involving virus isolation, in-house IgM and IgG capture ELISAs, and plaque reduction neutralization tests (PRNT) to determine the infection status of the individual. The primary endpoints were the clinical sensitivities and specificities of these devices. The SD Bioline Dengue Duo had an overall sensitivity of 87.3% (95% confidence interval [CI], 84.1 to 90.2%) and specificity of 86.8% (95% CI, 83.9 to 89.3%) during the first 14 days post-symptom onset (p.s.o.). The Panbio Dengue Duo Cassette demonstrated a sensitivity of 92.1% (87.8 to 95.2%) and specificity of 62.2% (54.5 to 69.5%) during days 4 to 14 p.s.o. The Panbio IgM capture ELISA had a sensitivity of 87.6% (82.7 to 91.4%) and specificity of 88.1% (82.2 to 92.6%) during days 4 to 14 p.s.o. Finally, the Panbio IgG capture ELISA had a sensitivity of 69.6% (62.1 to 76.4%) and a specificity of 88.4% (82.6 to 92.8%) during days 4 to 14 p.s.o. for identification of secondary dengue infections. This multicountry prospective study resulted in reliable real-world performance data that will facilitate data-driven laboratory test choices for managing patient care during dengue outbreaks.

Comparison of the Sofia and Veritor direct antigen detection assay systems for identification of influenza viruses from patient nasopharyngeal specimens.

Influenza antigen detection assays (Sofia fluorescent immunoassay [FIA] and Veritor) yield objective results, which are potentially useful for point-of-care testing. The assays were evaluated with reverse transcriptase PCR (RT-PCR) using 411 nasopharyngeal swab specimens. Sensitivity and specificity values (percentages) of 79.0/99.0 and 64.0/99.4 for influenza A and 92.9/96.7 and 78.6/98.7 for influenza B were obtained for the Sofia and Veritor assays, respectively.