Can newly developed, rapid immunochromatographic antigen detection tests be reliably used for the laboratory diagnosis of influenza virus infections?

Pathogenesis, Diagnosis, and Treatment of Infectious Rhinosinusitis

Rhinosinusitis is a common inflammatory disease of the sinonasal mucosa and paranasal sinuses. The pathogenesis of rhinosinusitis involves a variety of factors, including genetics, nasal microbiota status, infection, and environmental influences. Pathogenic microorganisms, including viruses, bacteria, and fungi, have been proven to target the cilia and/or epithelial cells of ciliated airways, which results in the impairment of mucociliary clearance, leading to epithelial cell apoptosis and the loss of epithelial barrier integrity and immune dysregulation, thereby facilitating infection. However, the mechanisms employed by pathogenic microorganisms in rhinosinusitis remain unclear. Therefore, this review describes the types of common pathogenic microorganisms that cause rhinosinusitis, including human rhinovirus, respiratory syncytial virus, Staphylococcus aureus, Pseudomonas aeruginosa, Aspergillus species, etc. The damage of mucosal cilium clearance and epithelial barrier caused by surface proteins or secreted virulence factors are summarized in detail. In addition, the specific inflammatory response, mainly Type 1 immune responses (Th1) and Type 2 immune responses (Th2), induced by the entry of pathogens into the body is discussed. The conventional treatment of infectious sinusitis and emerging treatment methods including nanotechnology are also discussed in order to improve the current understanding of the types of microorganisms that cause rhinosinusitis and to help effectively select surgical and/or therapeutic interventions for precise and personalized treatment.

[Virological diagnosis of lower respiratory tract infections]

INTRODUCTION

The etiological diagnosis of bronchopulmonary infections cannot be assessed with clinical, radiological and epidemiological data alone. Viruses have been demonstrated to cause a large proportion of these infections, both in children and adults.

BACKGROUND

The diagnosis of viral bronchopulmonary infections is based on the analysis of secretions, collected from the lower respiratory tract when possible, by techniques that detect either influenza and respiratory syncytial viruses, or a large panel of viruses that can be responsible for respiratory disease. The latter, called multiplex PCR assays, allow a syndromic approach to respiratory infection. Their high cost for the laboratory raises the question of their place in the management of patients in terms of antibiotic economy and isolation. In the absence of clear recommendations, the strategy and equipment are very unevenly distributed in France.

OUTLOOK

Medico-economic analyses need to be performed in France to evaluate the place of these tests in the management of patients. The evaluation of the role of the different viruses often detected in co-infection, especially in children, also deserves the attention of virologists and clinicians.

CONCLUSIONS

The availability of new diagnostic technologies, the recent emergence of SARS-CoV-2, together with the availability of new antiviral drugs are likely to impact future recommendations for the management of viral bronchopulmonary infections.

Impact of Rapid Influenza Molecular Testing on Management in Pediatric Acute Care Settings

OBJECTIVES

To measure the impact of rapid influenza real-time qualitative reverse transcriptase polymerase chain reaction (RT-PCR) on patient management in busy pediatric emergency department (ED) and urgent care clinic settings.

STUDY DESIGN

We developed a brief, elective survey that clinicians completed when an influenza RT-PCR order was placed in the ED or urgent care clinic between February 18, 2019, and March 13, 2019. We captured the clinical suspicion for influenza, intended management plans, and actual management plans once influenza RT-PCR results were available.

RESULTS

We evaluated 339 encounters, of which 164 (48.4%) had a positive influenza RT-PCR. Clinical suspicion for influenza was a nonsignificant predictor for influenza PT-PCR positivity (P = .126). After rapid influenza RT-PCR results were available, clinicians changed their original plans in 44.5% of influenza RT-PCR positive vs 92.6% of influenza RT-PCR negative cases (P < .0001). Change in plans for antiviral use was observed in 26% of influenza positive vs 77% of influenza negative cases (P < .0001). A total of 135 antiviral prescriptions were avoided in patients with negative influenza RT-PCR.

CONCLUSIONS

Implementation of a rapid and accurate influenza RT-PCR in the acute care setting is important to systematically diagnose influenza in children and improve outpatient management decisions, because clinical suspicion for influenza is inaccurate. A negative influenza RT-PCR decreases unnecessary antiviral use and has the potential for significant cost savings.

Implementing COVID-19 (SARS-CoV-2) Rapid Diagnostic Tests in Sub-Saharan Africa: A Review

Introduction: For the COVID-19 (SARS-CoV-2) response, COVID-19 antigen (Ag), and antibody (Ab) rapid diagnostic tests (RDTs) are expected to complement central molecular testing particularly in low-resource settings. The present review assesses requirements for implementation of COVID-19 RDTs in sub-Saharan Africa. Methods: Review of PubMed-published articles assessing COVID-19 RDTs complemented with Instructions for Use (IFU) of products. Results: In total 47 articles on two COVID-19 Ag RDTs and 54 COVID-19 Ab RDTs and IFUs of 20 COVID-19 Ab RDTs were retrieved. Only five COVID-19 Ab RDTs (9.3%) were assessed with capillary blood sampling at the point-of-care; none of the studies were conducted in sub-Saharan Africa. Sampling: Challenges for COVID-19 Ag RDTs include nasopharyngeal sampling (technique, biosafety) and sample stability; for COVID-19 Ab RDTs equivalence of whole blood vs. plasma/serum needs further validation (assessed for only eight (14.8%) products). Sensitivity-Specificity: sensitivity of COVID-19 Ag and Ab RDTs depend on viral load (antigen) and timeframe (antibody), respectively; COVID-19 Ab tests have lower sensitivity compared to laboratory test platforms and the kinetics of IgM and IgG are very similar. Reported specificity was high but has not yet been assessed against tropical pathogens. Kit configuration: For COVID-19 Ag RDTs, flocked swabs should be added to the kit; for COVID-19 Ab RDTs, finger prick sampling materials, transfer devices, and controls should be added (currently only supplied in 15, 5, and 1/20 products). Usability and Robustness: some COVID-19 Ab RDTs showed high proportions of faint lines (>40%) or invalid results (>20%). Shortcomings were reported for buffer vials (spills, air bubbles) and their instructions for use. Stability: storage temperature was ≤ 30°C for all but one RDT, in-use and result stability were maximal at 1 h and 30 min, respectively. Integration in the healthcare setting requires a target product profile, landscape overview of technologies, certified manufacturing capacity, a sustainable market, and a stringent but timely regulation. In-country deployment depends on integration in the national laboratory network. Discussion/Conclusion: Despite these limitations, successful implementation models in triage, contact tracing, and surveillance have been proposed, in particular for COVID-19 Ab RDTs. Valuable experience is available from implementation of other disease-specific RDTs in sub-Saharan Africa.

Cost-Effective Respiratory Virus Testing

The timely and accurate diagnosis of respiratory virus infections has the potential to optimize downstream (posttesting) use of limited health care resources, including antibiotics, antivirals, ancillary testing, and inpatient and emergency department beds. Cost-effective algorithms for respiratory virus testing must take into consideration numerous factors, including which patients should be tested, what testing should be performed (for example, antigen testing versus reverse transcription-PCR testing or influenza A/B testing versus testing with a comprehensive respiratory virus panel), and the turnaround time necessary to achieve the desired posttesting outcomes. Despite the clinical impact of respiratory virus infections, the cost-effectiveness of respiratory virus testing is incompletely understood. In this article, we review the literature pertaining to the cost-effectiveness of respiratory virus testing in pediatric and adult patient populations, in emergency department, outpatient, and inpatient clinical settings. Furthermore, we consider the cost-effectiveness of a variety of testing methods, including rapid antigen tests, direct fluorescent antibody assays, and nucleic acid amplification tests.

Analytical performances of the BD Veritor™ System for the detection of respiratory syncytial virus and influenzaviruses A and B when used at bedside in the pediatric emergency department

This study aims to evaluate the analytical performance of the BD Veritor™ rapid diagnostic assays (RDTs) for respiratory syncytial virus (RSV) and influenzaviruses when performed 24/7 at bedside by nurses in the pediatric emergency department (PED). The study was performed between 14/10/2015 and 19/03/2016 on nasopharyngeal aspirates (NPAs) collected from children consulting at the PED of the University Hospital of Saint-Etienne for bronchiolitis (RSV detection) or flu-like syndrome (influenzaviruses A/B detection). NPAs were tested 24/7 at the PED with the RDT and then sent to the Infectious Agents Department for routine analyses, first by immunofluorescence assay (IFA), then by nucleic acid amplification test (NAAT) considered as the gold standard in case of discrepancy between RDT and IFA results. For RSV detection, 205 NPAs was analyzed; the overall concordance between RDT and routine assays was of 97.6% (200/205). The sensitivity (Se), specificity (Sp), negative predictive value (NPV) and positive predictive value (PPV) were of 97.6% (160/164), 97.6% (40/41), 90.9% (40/44) and 99.4% (160/161), respectively. A total of 419 NPA was tested for influenzaviruses. For influenzavirus A, the overall concordance was of 98.8% (414/419); Se, Sp, NPV and PPV were of 100% (41/41), 98.7% (373/378), 100% (373/373) and 89.1% (41/46), respectively. For influenzavirus B, the overall concordance was of 97.9% (410/419); Se, Sp, NPV and PPV were of 96.6% (172/178), 98.8% (238/241), 97.5% (238/244) and 98.3% (172/175), respectively. Due to their excellent performances and their easy handle by non-laboratory personnel, these RDTs can be warmly recommended as point of care assays at the PED.

Inorganic Complexes and Metal-Based Nanomaterials for Infectious Disease Diagnostics

Infectious diseases claim millions of lives each year. Robust and accurate diagnostics are essential tools for identifying those who are at risk and in need of treatment in low-resource settings. Inorganic complexes and metal-based nanomaterials continue to drive the development of diagnostic platforms and strategies that enable infectious disease detection in low-resource settings. In this review, we highlight works from the past 20 years in which inorganic chemistry and nanotechnology were implemented in each of the core components that make up a diagnostic test. First, we present how inorganic biomarkers and their properties are leveraged for infectious disease detection. In the following section, we detail metal-based technologies that have been employed for sample preparation and biomarker isolation from sample matrices. We then describe how inorganic- and nanomaterial-based probes have been utilized in point-of-care diagnostics for signal generation. The following section discusses instrumentation for signal readout in resource-limited settings. Next, we highlight the detection of nucleic acids at the point of care as an emerging application of inorganic chemistry. Lastly, we consider the challenges that remain for translation of the aforementioned diagnostic platforms to low-resource settings.

Impact of bedside diagnosis of influenza in the paediatric emergency ward

OBJECTIVES

This prospective study performed in the paediatric emergency department of the University Hospital of Saint-Etienne aimed to measure the impact of the 24/7 bedside use of the Veritor™ System (Becton Dickinson) on the reduction of supplementary investigations, hospital stay and antimicrobial use.

METHODS

Influenza virus A and B antigens were detected with a rapid influenza digital immunoassay (DIA) on nasopharyngeal aspirates (NPAs) sampled from the children consulting at the paediatric emergency department between January and March 2016 for influenza-like illness. The same NPA was tested by immunofluorescence and/or molecular routine assays. Before performing the DIA, the clinician filled in a questionnaire listing the tests that he/she would have prescribed in the absence of the rapid testing. The prescription of complementary investigations, antimicrobial treatments and hospital stay were also compared to those of the 3 previous years.

RESULTS

A total of 514 children with flu-like symptoms were included. The use of the DIA at bedside decreased the prescription of blood puncture by 47.9% (21.2% to 6.6%), of chest X-rays by 69.0% (33.3% to 10.3%), of lumbar puncture by 77.8% (7.0% to 1.6%), of urine culture by 79.2% (23.3% to 4.9%), of antibiotic treatments by 70.1% (16.9% to 5.1%), and of hospital stay by 25.0% (27.2% to 20.4%), resulting in a reduction of medical costs estimated to more than €69 000 in a season.

CONCLUSIONS

In addition to delivering a rapid aetiological diagnosis, this strategy saves medical costs and favours an antimicrobial stewardship strategy. However, further prospective studies are needed to confirm our findings.

Influenza vaccine showed a good preventive effect against influenza-associated hospitalization among elderly patients, during the 2016/17 season in Japan

The 2016/17 influenza season in Japan was characterized by a predominance of influenza A (H3N2) activity; with H3N2 accounting for 85% of all detected influenza virus infections. We assessed the vaccine effectiveness (VE) of an inactivated quadrivalent influenza vaccine (IIV4) in adult patients, using a test-negative case-control design study based on the results of a rapid influenza diagnostic test (RIDT). Between November 2016 and March 2017, a total of 1048 adult patients were enrolled: including 363 RIDT positive for influenza A, 9 RIDT-positive for influenza B, and 676 RIDT-negative. During the 2016/17 season, the overall adjusted VE was 28.8% (95% confidence interval [CI]: 6.3-46%). The adjusted VE against influenza A was 27.4% (95%CI: 4.4-45%). The VE against influenza B could not be estimated because of the very low number of influenza B patients. Twenty-nine patients were hospitalized due to influenza-associated illness-during the present study, all of whom were infected with influenza A virus. The adjusted VE, determined using a case-control study, for preventing hospitalization for influenza A infection was 72.6% (95%CI: 30.7-89.1%). In addition, the VE for preventing hospitalization of influenza patients with comorbidities was 78.2% (95%CI: 41.1-92%). Our study showed that, during the 2016/17season, IIV4 was effective for preventing both the onset of influenza and influenza-associated hospitalization.

Multicenter evaluation of the Alere™ i influenza A&B assay using respiratory specimens collected in viral transport media

Rapid and accurate detection of influenza virus is critical for proper patient management. The Alere™ i Influenza A&B assay is an isothermal nucleic acid amplification test capable of detecting influenza A and B viruses directly from respiratory specimens. In this multicenter clinical trial conducted in the US, we evaluated the clinical performance of the Alere™ i Influenza A&B assay against that of the Prodesse ProFlu+ assay. A total of 1243 fresh, leftover nasal or nasopharyngeal swabs eluted in viral transport medium were tested by both assays. Sensitivity and specificity of the Alere™ i Influenza A&B assay were 97.8% (95% CI 94.6-99.2) and 96.6% (95% CI 95.2-97.5) for influenza A and 92.9% (95% CI 85.5-96.9) and 98.3% (95% CI 97.4-98.0) for influenza B. The Alere™ i Influenza A&B assay is an ideal molecular assay for influenza virus detection due to its high sensitivity and specificity with minimal hands-on and turn-around-time.

Detection of Influenza A and B Viruses and Respiratory Syncytial Virus by Use of Clinical Laboratory Improvement Amendments of 1988 (CLIA)-Waived Point-of-Care Assays: a Paradigm Shift to Molecular Tests

An accurate laboratory diagnosis of influenza, respiratory syncytial virus (RSV), and other respiratory viruses can help to guide patient management, antiviral therapy, infection prevention strategies, and epidemiologic monitoring. Influenza has been the primary driver of rapid laboratory testing due to its morbidity and mortality across all ages, the availability of antiviral therapy, which must be given early to have an effect, and the constant threat of new pandemic strains. Over the past 30 years, there has been an evolution in viral diagnostic testing, from viral culture to rapid antigen detection, and more recently, to highly sensitive nucleic acid amplification tests (NAAT), as well as a trend to testing at the point of care (POC). Simple rapid antigen immunoassays have long been the mainstay for POC testing for influenza A and B viruses and respiratory syncytial virus (RSV) but have been faulted for low sensitivity. In 2015, the first POC NAAT for the detection of influenza was approved by the Food and Drug Administration (FDA), ushering in a new era. In 2017, the FDA reclassified rapid influenza diagnostic tests (RIDTs) from class I to class II devices with new minimum performance standards and a requirement for annual reactivity testing. Consequently, many previously available RIDTs can no longer be purchased in the United States. In this review, recent developments in Clinical Laboratory Improvement Amendments of 1988 (CLIA)-waived testing for respiratory virus infections will be presented, with the focus on currently available FDA-cleared rapid antigen and molecular tests primarily for influenza A and B viruses and RSV.

Magnetic Nanozyme-Linked Immunosorbent Assay for Ultrasensitive Influenza A Virus Detection

Rapid and sensitive detection of influenza virus is of soaring importance to prevent further spread of infections and adequate clinical treatment. Herein, an ultrasensitive colorimetric assay called magnetic nano(e)zyme-linked immunosorbent assay (MagLISA) is suggested, in which silica-shelled magnetic nanobeads (MagNBs) and gold nanoparticles are combined to monitor influenza A virus up to femtogram per milliliter concentration. Two essential strategies for ultrasensitive sensing are designed, i.e., facile target separation by MagNBs and signal amplification by the enzymelike activity of gold nanozymes (AuNZs). The enzymelike activity was experimentally and computationally evaluated, where the catalyticity of AuNZ was tremendously stronger than that of normal biological enzymes. In the spiked test, a straightforward linearity was presented in the range of 5.0 × 10^-15-5.0 × 10^-6g·mL^-1 in detecting the influenza virus A (New Caledonia/20/1999) (H1N1). The detection limit is up to 5.0 × 10^-12 g·mL^-1 only by human eyes, as well as up to 44.2 × 10^-15 g·mL^-1 by a microplate reader, which is the lowest record to monitor influenza virus using enzyme-linked immunosorbent assay-based technology as far as we know. Clinically isolated human serum samples were successfully observed at the detection limit of 2.6 PFU·mL^-1. This novel MagLISA demonstrates, therefore, a robust sensing platform possessing the advances of fathomable sample separation, enrichment, ultrasensitive readout, and anti-interference ability may reduce the spread of influenza virus and provide immediate clinical treatment.

Clinical decision making in the emergency department setting using rapid PCR: Results of the CLADE study group

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The influence of an influenza diagnosis on patient managed during ED visits is examined.

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An influenza diagnosis in the ED is actionable, impacting empiric management in 61% of cases.

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The clinical diagnosis of influenza, based on presenting symptoms, lacks sensitivity at 36%.

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A 30 min result from collection to report could be achieved in the ED for 91.7%, of cases tested.

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ED testing resulted in savings of $200.40/ED visit but is dependent on avoiding planned admissions.

Background

Emergency Departments (ED) are challenged during influenza season by patients who present acutely during sporadic ED visits. ED management is largely empiric, often occurring without reliable diagnostics needed for targeted therapies, safe outpatient discharge, or hospital admissions.

Objective

To evaluate the impact of the influenza diagnosis on physician decision making during ED visits using the Cobas Liat^® influenza A + B assay.

Study design

Prospective study assessing the impact of rapid (<30 min), reverse-transcriptase polymerase chain reaction (RT-PCR) influenza testing on physician decision making in the ED. Physician responses established pre-and post-diagnosis management courses which required confirmation via secondary documentation in the medical record. Changes in physician decision making were analyzed across four clinical touchpoints: (i) admission/discharge status, (ii) medical procedures, (iii) antiviral and antibiotic prescribing, and (iv) laboratory studies.

Results

An influenza diagnosis changed patient management courses, relative to empiric, pre-diagnosis plans, in in 61% of the cases resulting in cost savings of $49,420-to-$42,270 over 143 patients and 104 days during influenza season resulting in a cost savings of $200.40/ED visit. Evaluation over 2000 ED patient visits projects cost savings > $578,000 due to deferred admissions, and reduction in antiviral prescribing. Sensitivity of ED-based influenza testing using the Cobas Liat^® assay was equivalent to centralized lab testing at 98.8% sensitivity and 98.5% specificity respectively.

Conclusion

Providing rapid, RT-PCR influenza testing to ED settings is actionable and used to guide patient care decisions. Understanding the cascade of events linked to the influenza diagnosis in the ED provides overall cost savings which offset the cost of providing ED-based testing.

Diagnostic performances of the Xpert® Flu PCR test and the OSOM® immunochromatographic rapid test for influenza A and B virus among adult patients in the Emergency Department

BACKGROUND

New rapid influenza diagnostic tests (RIDT) are available but their clinical utility in adults has not been validated.

OBJECTIVES

To evaluate the diagnostic performances of OSOM^® Ultra Flu A&B a RIDT on viral strains of influenza A/B from the last epidemic season, and its feasibility by Emergency Department (ED) physicians and nurses.

STUDY DESIGN

Of the 1099 patients admitted to the ED with suspected influenza, all having a nasopharyngeal swab tested by the Xpert^® Flu PCR and then stored at -20 °C; 500 were selected at random and their samples were tested using the RIDT. Two experts reviewed ED and hospital medical records and all virological data to define influenza cases. Intra- and inter-observer variability were calculated.

RESULTS

Of the 500 patients included 45% were ≥75 years, 122 (24.4%) presented with influenza based on clinical and virological criteria. PCR test performances (%) were Se 98.4 (95% CI 93.6-99.7), Spe 99.7 (98.3-100), PPV 99.2 (94.8-100) and NPV 99.5 (97.9-100); and RIDT performances were Se 95.1 (89.2-97.9), Spe 98.4 (96.4-99.4), PPV 95.1 (87.2-99.9) and NPV 98.4 (96.4-98). There was no difference in test performance between influenza A and B virus nor between the influenza A subtypes. Intra- and inter-observer variability of RIDT were 0.94 (0.89-0.99) and 0.96 (0.92-1).

CONCLUSION

Our results show that the Xpert^® Flu PCR and the OSOM^® Ultra Flu A&B Test perform very well in diagnosing strains of circulating virus in adults and elderly. Our results also confirm the feasibility of this RIDT at point-of-care by ED staff.

Impact of Respiratory Virus Infections in Exacerbation of Acute and Chronic Rhinosinusitis

Rhinosinusitis (RS) is a symptomatic disease classification of many causes and is a major economic burden worldwide. It is widely accepted that RS is further classified into acute (ARS) and chronic (CRS) rhinosinusitis based on the duration of the symptoms, and that viral infection plays a large role in initiating or potentiating the disease. In this review, we examine the role of respiratory virus infection in the exacerbation of ARS and CRS. We explore the epidemiology of viral exacerbation of ARS and CRS and highlight key viruses that may cause exacerbation. We also review the current understanding of viral infections in the upper airway to further explain the putative underlying mechanisms of inflammatory events in ARS and CRS exacerbation. Advances in accurate diagnosis of the etiologic respiratory viruses of ARS and CRS symptoms which can lead to better disease management are also surveyed. In addition to the current treatments which provide symptomatic relief, we also explore the potential of harnessing existing antiviral strategies to prevent ARS and CRS exacerbation, especially with improved viral diagnostic tools to guide accurate prescription of antivirals against causative respiratory viruses.

Respiratory RNA Viruses

Acute upper and lower respiratory infections are a major public health problem and a leading cause of morbidity and mortality worldwide. At greatest risk are young children, the elderly, the chronically ill, and those with suppressed or compromised immune systems. Viruses are the predominant cause of respiratory tract illnesses and include RNA viruses such as respiratory syncytial virus, influenza virus, parainfluenza virus, metapneumovirus, rhinovirus, and coronavirus. Laboratory testing is required for a reliable diagnosis of viral respiratory infections, as a clinical diagnosis can be difficult since signs and symptoms are often overlapping and not specific for any one virus. Recent advances in technology have resulted in the development of newer diagnostic assays that offer great promise for rapid and accurate detection of respiratory viral infections. This chapter emphasizes the fundamental characteristics and clinical importance of the various RNA viruses that cause upper and lower respiratory tract diseases in the immunocompromised host. It highlights the laboratory methods that can be used to make a rapid and definitive diagnosis for the greatest impact on the care and management of ill patients, and the prevention and control of hospital-acquired infections and community outbreaks.

SOFIA®RSV: prospective laboratory evaluation and implementation of a rapid diagnostic test in a pediatric emergency ward

Background

Respiratory syncytial virus (RSV) is responsible for severe respiratory infections and higher costs in medical care. The two aims of this work were to assess the performances of SOFIA^®RSV tests in “real-life-laboratory” conditions (study 1) and implemented at point-of-care testing in a pediatric emergency department (ED, study 2), during two consecutive winter seasons.

Methods

In study 1, fresh nasopharyngeal swabs from patients of all ages were sampled in 1.5 ml of Universal virological Transport Medium (UTM) and prospectively tested using SOFIA^®RSV tests. In study 2, conducted in a pediatric ED, nasopharyngeal swabs were placed in 3 ml of UTM. All SOFIA^®RSV tests were confirmed by molecular testing, considered as reference method. The epidemiological and clinical features of tested patients, as well as the care of these patients after obtaining quick results were evaluated.

Results

The sensitivities of SOFIA^®RSV in infants (aged under 24 months) performed in the laboratory and in the pediatric ED were respectively 95% (95% CI: 86.8–98.1) and 74.8% (95% CI: 68.0–80.9) compared to PCR. In study 1, the sensitivity among children (from 2 to 15 years old) and adults (above 15 years old) dropped to 45% (95% CI: 23.1–68.5) and 59% (95% CI: 32.9–81.6), respectively. In study 2, there were some differences in bed-management of SOFIA^®RSV positive compared to SOFIA^®RSV negative infants.

Conclusions

SOFIA^®RSV tests performed in the laboratory and in the pediatric ED show high and satisfactory sensitivities among young children under 24 months, which supports its robustness and reliability. However, the impact of these tests on patient care at point-of-care cannot be clearly assessed when considering the limits of the study 2 design.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2557-8) contains supplementary material, which is available to authorized users.

Rapid detection of avian influenza virus H5N1 in chicken tracheal samples using an impedance aptasensor with gold nanoparticles for signal amplification

Highly pathogenic avian influenza virus H5N1 is a continuous threat to public health and poultry industry. The recurrence of the H5N1 led us to develop a robust, specific, and rapid detection method for the virus. In this study, an impedance aptasensor was developed for the virus detection using specific H5N1 aptamer and a gold interdigitated microelectrode. Streptavidin was immobilized on the microelectrode surface and biotin labeled H5N1 aptamer was bound to the immobilized streptavidin. The microelectrode was blocked with the polyethylene glycol and the bound aptamer captured the virus. The impedance change caused by the captured virus was measured using an impedance analyzer. To enhance impedance signal, a nanoparticle-based amplifier was designed and implemented by forming a network-like gold nanoparticles/H5N1-aptamer/thiocyanuric acid. The detection limit of the impedance aptasensor was 0.25 HAU for the pure virus and 1 HAU for the tracheal chicken swab samples spiked with the H5N1 virus. The detection time of aptasensor without employing the amplifier was less than an hour. The amplifier increased impedance by a 57-fold for the 1 HAU samples. Only negligible impedance change was observed for non-target viruses such as H5N2, H5N3, H7N2, H1N1, and H2N2. This aptasensor provides a foundation for the development of a portable aptasensor instrument.

Severe sensitivity loss in an influenza A molecular assay due to antigenic drift variants during the 2014/15 influenza season

The 2014-2015 influenza season in Belgium was dominated by the circulation of 2 influenza A(H3N2) subgroups: 3C.2a and 3C.3b. Analysis of 166 nasopharyngeal aspirates, collected in patients with respiratory illness at the start of the epidemic season, showed a decreased sensitivity for the detection of influenza A(H3N2)/3C.2a using a commercially available multiplex assay. Gene sequencing of the matrix protein showed a point mutation (C163T) leading to a mismatch with the assay probes.

Analytical performance of the Alere™ i Influenza A&B assay for the rapid detection of influenza viruses

The analytical performance of the new Alere™ i Influenza A&B kit (AL-Flu) assay, based on isothermal nucleic acids amplification, was evaluated and compared with an antigen detection method, SD Bioline Influenza Virus Antigen Test (SDB), and an automated real-time RT-PCR, Simplexa™ Flu A/B & VRS Direct assay (SPX), for detection of influenza viruses. An “in-house” RT-PCR was used as the reference method. Sensitivity of AL-Flu, SDB, and SPX was 71.7%, 34.8%, and 100%, respectively. Specificity was 100% for all techniques. The turnaround time was 13 min for AL-Flu, 15 min for SDB, and 75 min for SPX.

The Alere™ i Influenza A&B assay is an optimal point-of-care assay for influenza diagnosis in clinical emergency settings, and is more sensitive and specific than antigen detection methods.

Diagnostic Accuracy of Rapid Antigen Detection Tests for Respiratory Syncytial Virus Infection: Systematic Review and Meta-analysis

Respiratory syncytial virus (RSV) rapid antigen detection tests (RADT) are extensively used in clinical laboratories. We performed a systematic review and meta-analysis to evaluate the accuracy of RADTs for diagnosis of RSV infection and to determine factors associated with accuracy estimates. We searched EMBASE and PubMed for diagnostic-accuracy studies of commercialized RSV RADTs. Studies reporting sensitivity and specificity data compared to a reference standard (reverse transcriptase PCR [RT-PCR], immunofluorescence, or viral culture) were considered. Two reviewers independently extracted data on study characteristics, diagnostic-accuracy estimates, and study quality. Accuracy estimates were pooled using bivariate random-effects regression models. Heterogeneity was investigated with prespecified subgroup analyses. Seventy-one articles met inclusion criteria. Overall, RSV RADT pooled sensitivity and specificity were 80% (95% confidence interval [CI], 76% to 83%) and 97% (95% CI, 96% to 98%), respectively. Positive- and negative-likelihood ratios were 25.5 (95% CI, 18.3 to 35.5) and 0.21 (95% CI, 0.18 to 0.24), respectively. Sensitivity was higher in children (81% [95% CI, 78%, 84%]) than in adults (29% [95% CI, 11% to 48%]). Because of this disparity, further subgroup analyses were restricted to pediatric data (63 studies). Test sensitivity was poorest using RT-PCR as a reference standard and highest using immunofluorescence (74% versus 88%; P < 0.001). Industry-sponsored studies reported significantly higher sensitivity (87% versus 78%; P = 0.01). Our results suggest that the poor sensitivity of RSV RADTs in adults may preclude their use in this population. Furthermore, industry-sponsored studies and those that did not use RT-PCR as a reference standard likely overestimated test sensitivity.

Performance Characteristics of Xpert Flu/RSV XC Assay

The Xpert Flu/RSV XC assay was compared to laboratory-developed tests (LDTs) (n = 207) and the Xpert Flu assay (n = 147) using archived nasopharyngeal swabs. The percentages of positive agreements with LDTs were 97.8% for influenza A, 97.2% for influenza B, and 89.3% for RSV. The sensitivity of influenza detection was improved with the Xpert Flu/RSV XC assay compared to the Xpert Flu assay.