Diagnosis Of Influenza Virus Infection Research Articles

Death in children with influenza A (H3N2) virus infection-associated encephalopathy: two case reports

We herein report two cases involving children who died of influenza A (H3N2) virus infection-associated encephalopathy/encephalitis (IAE). Both children developed convulsions and impaired consciousness within a relatively short period and eventually died of brainstem failure. Patient 1 presented with high fever, vomiting, and diarrhea. Laboratory tests indicated persistently high lactate, alanine aminotransferase, and urea nitrogen concentrations in the blood as well as a high protein concentration in the cerebrospinal fluid. Patient 2 presented with persistent hyperthermia and progressive disturbance of consciousness, but the cerebrospinal fluid remained normal during the disease course. Both patients were actively given oseltamivir antiviral treatment after diagnosis of influenza virus infection. However, the disease progressed and invasive mechanical ventilation was performed. Both children's condition quickly progressed to IAE, and they eventually died. IAE is a rare complication of influenza virus infection with high mortality, and its pathogenesis remains unclear. The purpose of this report is to draw attention to the serious central nervous system complications of influenza infection and raise awareness of the fatal consequences of this disease among pediatricians.

Evaluation of a New Rapid Antigen Detection Test for the Diagnosis of Influenza Virus Infection in a Tertiary Care Hospital of Southern India

Introduction: Rapid antigen testing can help in early diagnosis of Influenza in resource limited settings in patients presenting with Influenza Like Illness (ILI). Aim: To evaluate the usefulness of Rapid Influenza Direct antigen Testing (RIDT) in comparison to Real Time Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) for diagnosis of Influenza virus infection in clinically suspected patients with ILI in a tertiary care hospital. Material and Methods: A prospective observational independent study was done to evaluate RIDT for Influenza virus infection, considering RT-PCR as gold standard. Throat swabs and nasal swabs from patients meeting Category 3 definition of ILI by Ministry Of Health and Family Welfare (MOHFW) were collected from July 20th, 2019 to October 20th, 2019 from hospitals in and around the study area. Onsite Rapid test (Biogenix, China) was used as per manufactures instructions for rapid detection of Influenza antigen. RNA extraction was done using Qiagen kit followed by RT-PCR using primer, probes recommended by National Institute of Virology (NIV, Pune) as per their protocols. Data was recorded on a predesigned proforma and managed using Microsoft Excel 2018 (Microsoft Corp, Redmond, WA). The Statistical software MedCalc version 9.1 for Windows was used for data analysis. Results: The overall sensitivity of the RIDT was 37.9% and specificity was 94.4%. The Positive Predictive Value (PPV) and Negative Predictive Value (NPV) were 73.3% and 78.8%, respectively. Kappa was calculated to be 0.37 that suggested a fair agreement between RIDT and RT-PCR. When the Cycle threshold (Ct) values were compared to the results of RIDT, there were more false positives at low Ct value and more false negatives at high Ct values. Conclusion: The RIDT is not useful in screening during an outbreak in acute care settings. The negative result of RIDT should be followed up with RT-PCR. With a strong clinical suspicion, it is better to start antivirals than wait for laboratory report in severely ill patients with ILI.

Role of hematological parameters in the diagnosis of influenza virus infection in patients with respiratory tract infection symptoms.

BackgroundThe differential diagnoses of patients hospitalized for respiratory infections due to influenza virus vs other pathogens are challenging. Our study investigated whether hematological parameters such as neutrophil (N), lymphocyte (L), platelet (PLT), and neutrophil‐to‐lymphocyte ratio (NLR) contributed in diagnosing influenza virus infections and in discriminating other respiratory infections.MethodsWe retrospectively analyzed the laboratory characteristics of 307 patients with respiratory infections caused by influenza/non‐influenza virus and bacteria. The diagnostic abilities of hematological indexes were evaluated in the patients compared with 100 healthy people.ResultsThe hematological parameters in patients with influenza virus infection were dramatically altered compared with those in the controls. Additionally, among the systemic inflammatory markers, the sensitivity of NLR for influenza detection was higher than that of N and L. PLT was significantly lower in influenza virus‐positive infection than in influenza virus‐negative infection. Moreover, when patients with influenza virus infection were cured, PLT returned to a normal level. The red blood cell (RBC) and hemoglobin (Hb) levels of influenza virus infection were higher than those of bacterial infection. Compared with traditional N and L, NLR and platelet‐to‐neutrophil (PNR) showed greater significance between influenza virus and bacterial infection (P < .01).ConclusionNeutrophil‐to‐lymphocyte ratio with high sensitivity is a preferable diagnostic tool to screen influenza virus‐infected patients than N and L. PLT accounts in the differential diagnoses of respiratory infections due to influenza virus and other pathogens among patients. In addition, RBC, Hb, NLR, and PNR can significantly differentiate between influenza virus infections and bacterial infections.

Transient depression of myocardial function after influenza virus infection: A study of echocardiographic tissue imaging.

BackgroundInfluenza virus infection (IVI) was reported to be associated with minor cardiac changes, mostly those detected on electrocardiogram with and without elevated blood markers of myocardial injury; however, the characteristics of myocardial involvement in association with IVI are poorly understood. This study used echocardiographic tissue imaging (tissue Doppler, strain, and strain rate) to evaluate changes in left atrial (LA) and left ventricular (LV) myocardial function after IVI.Methods and resultsWe examined 20 adult individuals (mean age, 43 years) at 2 and 4 weeks after diagnosis of IVI. For myocardial functional variables, we obtained LV global longitudinal strain (GLS), LV early diastolic strain rate (e'sr), LA strain, and LA stiffness (E/e’/LA strain), in addition to data on tissue Doppler (s’, e’, and a’) and myocardial performance index. Blood markers of myocardial injury were also examined. During follow-up, there were no significant changes in global chamber function such as LV ejection fraction, E/e’, and LA volume. However, significant changes in myocardial function were observed, namely, in s’ (8.0 ± 1.6 cm/s to 9.3 ± 1.5 cm/s; p = 0.01), e’ (10.2 ± 2.8 cm/s to 11.4 ± 3.0 cm/s; p < 0.001), e’sr (1.43 ± 0.44 1/s to 1.59 ± 0.43 1/s; p = 0.005), and LA strain (35 ± 8% to 40 ± 12%; p = 0.025), and the myocardial performance index (0.52 ± 0.20 to 0.38 ± 0.09; p = 0.009), but not in a’, LA stiffness, or GLS. Cardiac troponin T and creatinine kinase isoenzyme MB were not elevated significantly at any examination.ConclusionsMyocardial dysfunction during IVI recovery appeared to be transient particularly in the absence of myocardial injury. Echocardiographic tissue imaging may be useful to detect subclinical cardiac changes in association with IVI.

A Multi-Hemagglutinin-Based Enzyme-Linked Immunosorbent Assay to Serologically Detect Influenza A Virus Infection in Animals.

Mammals can play a role as an intermediate host in the emergence of mammalian-adapted reassortants or mutants of avian influenza A viruses, with pandemic potential. Therefore, detecting viral infection in animals followed by assessment of the hemagglutinin (HA) subtype of the agent is an indispensable process for risk assessment in pandemic preparedness. In this study, we tested the potential of an enzyme-linked immunosorbent assay as a rapid diagnosis method, using a panel of HA subtype antigens. By analyzing reference immune sera, we found that this novel assay could detect HA subtype-specific antibodies without considerable inter-subtypic cross-reactivities, contributing to diagnosis of influenza virus infection.

The utility of peripheral blood leucocyte ratios as biomarkers in infectious diseases: A systematic review and meta-analysis

To assess the utility of the neutrophil:lymphocyte (NLR), lymphocyte:monocyte (LMR) and platelet:lymphocyte ratios (PLR) as infection biomarkers. PubMed/MEDLINE, Embase and Cochrane databases were searched to identify eligible articles. Studies of diagnosis, severity or outcome were included. PROSPERO systematic review registration CRD42017075032. Forty studies were included, reporting on bacterial and viral infections, malaria, and critical illness due to sepsis. Ten studies reported an association of higher NLR with bacteraemia, supported by meta-analysis of patient-level data (five studies, n = 3320; AUC 0.72, p<0.0001) identifying a cut-off of >12.65. Two studies reported an association with lower LMR and diagnosis of influenza virus infection in patients with respiratory tract infection. Meta-analysis of patient-level data (n = 85; AUC 0.66, p = 0.01) identified a cut-off of ≤2.06. The directionality of associations between NLR and outcomes in heterogeneous cohorts of critically ill adults with sepsis varied. Potential clinical utility was also demonstrated in pneumonia (NLR), pertussis (NLR), urinary tract infection (NLR), diabetic foot infections (NLR) and Crimean Congo Haemorrhagic Fever (PLR). Longitudinal measurement of LMR during respiratory virus infection reflected symptoms and NLR during sepsis and bacteraemia predicted mortality. Peripheral blood leucocyte ratios are useful infection biomarkers, with the most evidence related to diagnosis of bacteraemia and influenza virus infection. In critical illness due to sepsis, a signal towards an association with NLR and outcomes exists, and NLR should be evaluated in future stratification models. Longitudinal measurement of ratios during infection could be informative. Overall, these biomarkers warrant further recognition and study in infectious diseases.

Research progress of detective techniques for influenza virus infections

Influenza is one of the most common and widespread respiratory diseases in humans.In addition to pose a serious threat to the susceptible and high-risk population, influenza has an important impact on public health.Rapid and accurate diagnosis of influenza virus infections is essential for administrating prompt antiviral treatments and undertaking effective prevention and control measures during seasonal epidemics and pandemics, which to reduce morbidity and mortality associated with influenza virus infections.Several different approaches are currently available for diagnosis of influenza infections in humans, including virus isolation, antigen detections, nucleic acid amplifications, etc.New diagnostic methods are being developed to overcome the limitations of some traditional detection methods.Here is an overview of diagnostic techniques for influenza virus infection. Key words: Influenza virus; Diagnosis; Virus isolation; Antigen detection; Nucleic acid amplification; Rapid diagnosis

Evaluation of a rapid isothermal nucleic acid amplification kit, Alere™ i Influenza A&B, for the detection of avian influenza viruses

Rapid and accurate diagnosis of influenza virus infection is essential for quick responses for both human and animal health. The Alere™ i Influenza A&B is a novel isothermal nucleic acid amplification kit that can detect and differentiate between influenza A and B viruses in human specimens in approximately 15 min. In the present study, the performance of the Alere™ i Influenza A&B kit was evaluated for its ability to detect avian influenza virus in chickens. The kit was able to detect representative avian influenza virus strains (hemagglutinin subtypes H1–H16, including the recently isolated H5 and H7 highly pathogenic avian influenza viruses), and the detection limit of the kit for these viruses varied between 10−1.4–102.1 50% egg-infective dose per test, which is higher than the analytical sensitivity of the antigen detection immunochromatography kit ESPLINE® A INFLUENZA. In experimentally infected chickens inoculated with a highly pathogenic avian influenza virus strain A/chicken/Hokkaido/002/2016 (H5N6), viral RNA was detected in the tracheal and cloacal swabs. These results indicate that this kit has the potential to be used as a rapid screening test of influenza A virus infection in chickens.

Development of a HA1-specific enzyme-linked immunosorbent assay against pandemic influenza virus A H1N1.

PurposeEnzyme-linked immunosorbent assay (ELISA) has been used in the diverse field to evaluate influenza virus infection; for the surveillance, diagnosis, efficacy evaluation, and development of the vaccine. The aim of this study was to establish an ELISA for detecting HA strain-specific antibodies using recombinant pandemic A H1N1 (pH1N1) HA1 (rHA1) protein.Materials and MethodsrHA1 was produced in baculovirus system. The clinical performance of the developed ELISA was validated using human serum samples, by comparison with standard methods for detecting a neutralizing antibody; hemagglutination inhibition (HI) assay and microneutralization test (MNT). The ability of the ELISA system to evaluate the efficacy test of an influenza vaccine was explored by measuring antibody levels in the serum of vaccinated mice.ResultsOur ELISA could detect anti-rHA1 antibody in influenza-infected patients and vaccinated subjects. Compared to HI assay and MNT as reference methods, our method showed good performance in detection of anti-rHA1 antibody. Detection of the anti-rHA1 antibody in vaccinated mice and its correlation with titers in HI assay was also proved in a mice model.ConclusionAn ELISA system using rHA1 of pH1N1 influenza virus was developed, and showed good clinical performance in diagnosis of influenza virus infection and evaluation of the vaccination efficacy in both human and animal models.

A novel PCR-based point-of-care method facilitates rapid, efficient, and sensitive diagnosis of influenza virus infection

ObjectiveThe aim of this single-centre study was the comparative analysis of the GeneXpert (Cepheid Inc.) and the LIAT (Roche) system for the rapid polymerase chain reaction (PCR)-based detection of influenza A (IA) and influenza B (IB) viruses. Patients and methodsDuring the 2017–2018 flu season, 651 prospectively collected samples (throat and nasal swabs) of patients with symptoms of influenza-like illness or acute respiratory infection were tested for the presence of IA and IB viruses using the GeneXpert and LIAT systems. To evaluate the usefulness for near-patient testing, a LIAT system was installed at the Department of Emergency Medicine, and sample testing was performed on site. Reference testing of all samples was performed with the Xpert Flu assay and for 313 samples in addition with the Xpert Xpress Flu/RSV (respiratory syncytial virus) assay at the central laboratory. Analysis of all samples was carried out within 24 hr after collection. ResultsOverall, 267 of the 651 samples analysed were positive for influenza viruses in at least one of the three assays investigated (IA, 88; IB, 179). The overall rates of agreement between the LIAT assay and the Xpert Flu assay was 96.0% for the detection of IA and IB viruses. The sensitivity and specificity of the LIAT assay compared to the Xpert Flu assay for the detection of IA was 98.80% (95% confidence interval (CI) 93.47–99.97%) and 99.12% (95% CI, 97.96% to 99.71%) and for the detection of IB 98.76% (95% CI 95.58–99.85%), and 96.33% (95% CI 94.26–97.81%), respectively. The LIAT assay showed a statistically significant higher detection rate of IB virus than the Xpert Flu assay (p <0.01). No significant difference was found between the detection rate of the LIAT assay and the Xpert Xpress Flu/RSV assay. The mean time to the availability of a definite test result was significantly shorter with the on-site LIAT system than the GeneXpert system (mean 59 min saving time; p <0.01). ConclusionThe LIAT system represents a robust and highly sensitive point-of-care device for the rapid PCR-based detection of influenza A and influenza B viruses.

Respiratory Viruses in a Primary Health Care Facility in Amsterdam, the Netherlands

Background Laboratory testing for respiratory tract infections (RTIs) is not routinely performed in primary care. Their etiology is usually unknown, and although RTIs are mainly of viral origin, the contribution of different respiratory viruses is uncertain. Our study aims to increase our insight into the epidemiology of respiratory viruses in primary care and to evaluate the accuracy of the general practitioner's (GP's) clinical diagnosis of influenza virus infection. Methods We prospectively recruited patients who presented with RTI symptoms at a primary care facility in Amsterdam, the Netherlands, during the 2015–2016 winter season. Demographic and clinical characteristics of patients were summarized using a questionnaire. Nasopharyngeal swabs were collected and tested with a multiplex polymerase chain reaction assay detecting 14 respiratory viruses. Results One or more respiratory viruses were present in 42.5% of the patients (n = 353). The most frequently detected viruses were rhinovirus (11.6%), human coronavirus (8.8%), and influenza A virus (7.6%). Sensitivity of GP's clinical diagnosis for influenza virus infection was 52.6% and specificity was 78.3%. Conclusions Despite the use of a sensitive polymerase chain reaction, a respiratory virus could be detected in less than half of the patients visiting the GP with RTI symptoms. It is difficult to clinically distinguish influenza from other causes of RTIs. Correct etiological diagnosis of RTIs is needed because it contributes to differential diagnosis, might give direction to development of specific antiviral therapies and vaccines, reduce unnecessary prescription of antibiotics, and clarifies the clinical spectrum of the different respiratory viruses.

Development and Characterization of Monoclonal Antibodies against Nucleoprotein for Diagnosis of Influenza A Virus.

Influenza, which is a highly contagious disease caused by the influenza A virus, continues to be a major health concern worldwide. Although the accurate and early diagnosis of influenza virus infection is important for controlling the spread of this disease and rapidly initiating antiviral therapy, the current influenza diagnostic kits are limited by their low sensitivity. In this study, we developed several new influenza nucleoprotein (NP)-specific monoclonal antibodies (mAbs) and compared their sensitivity and specificity of those with commercially available anti-NP mAbs. Three mAbs, designated M24.11, M34.3, and M34.33, exhibited higher reactivities to recombinant NPs and A/Puerto Rico/8/1934 (H1N1) viral lysates compared with the commercial mAbs, as assessed using enzyme-linked immunosorbent assays. M34.3 and M34.33 showed higher reactivities with A/California/04/09 (pandemic H1N1) and A/Philippines/2/82 (H3N2) viral lysates than the commercial mAbs. In contrast, M24.11 had marked reactivity with H3N2 but not with pandemic H1N1. Immunofluorescent confocal microscopy showed that the three mAbs effectively detected the presence of influenza virus in lung tissues of mice infected with A/Puerto Rico/8/1934. These results indicate that the newly developed M34.3 and M34.33 mAbs could be useful for the development of influenza diagnostics.

Detection of influenza virus infections by molecular and immunofluorescence methods

Influenza virus infections are extremely important for human health due to the occurence of seasonal epidemics and pandemics worldwide. Influenza is associated with high morbidity and may result in serious complications such as life threatening viral or bacterial pneumonia. Especially, young children, older adults, patients with chronic diseases such as heart, lung, kidney, and diabetes and immunosuppressed people are at higher risk for complications and death from influenza virus infections. The aim of this study was to determine the incidence of influenza type A and B virus infections and influenza A virus subtypes in hospitalized patients with respiratory tract infections by real-time reverse transcriptase-polymerase chain reaction (RT-PCR, Sacace, Italy), conventional RT-PCR and direct immunofluorescence antibody (DFA, Argene SA, France) tests. Nasopharyngeal swab specimens were collected from a total of 476 patients with respiratory tract symptoms by using flocked swabs (Copan Diagnostics, Italy) between 1 April 2012 and 31 December 2013. Influenza A virus was detected in 20.5% (98/476) and influenza B virus in 3.3% (16/476) of the cases by real-time RT-PCR test. During the study period, 63.3% of 98 influenza virus isolates were found as influenza A(H1N1)pdm09 and 36.7% were influenza A(H3N2) subtypes. Influenza A (H1N1) pdm09 subtype was observed in 12 cases in January 2013 and influenza A(H3N2) subtype was observed in 11 cases in December 2013 as the highest values. When the real-time RT-PCR test was regarded as the reference test, the sensitivities of DFA test for influenza A and B and conventional RT-PCR test with WHO primers (M30F2/08 and M264R3/08) for influenza A were detected as 72.4%, 75%, 96% and the specificities were detected as 99.2%, 99.5% and 100%, respectively. In conclusion, influenza A virus infection was detected rather high with a rate of 20.5% in the study group. The monitoring of influenza virus types and subtypes is required for the evaluation of influenza vaccine strains and circulating influenza viruses and for the identification of subtypes with pandemic potential. Planning for appropriate antiviral therapy using real-time RT-PCR in the early diagnosis of influenza virus infections will significantly contribute to the management of the patient's treatment. Thus, unnecessary drug use will be prevented and controlled with effective treatment of the disease at the time of infection.

Impact of severe hematological abnormalities in the outcome of hospitalized patients with influenza virus infection.

Although hematological abnormalities have been described among patients with influenza virus infection, little is known about their impact on the outcome of the patients. The aim of this study was to assess the frequency and clinical impact of severe hematological abnormalities in patients with confirmed influenza virus infection. This was an observational retrospective study including all adult patients with diagnosis of influenza virus infection hospitalized from January to May 2016 in our institution. Influenza virus infection was diagnosed by means of rRT-PCR assay performed on respiratory samples. Poor outcome was defined as a composite endpoint in which at least one of the following criteria had to be fulfilled: (a) respiratory failure, (b) SOFA ≥2, or (c) death. Two hundred thirty-nine patients were included. Applying the HLH-04 criteria for the diagnosis of hemophagocytic syndrome, cytopenias (hemoglobin ≤9 g/dl, platelets <100,000/μl or neutrophils <1,000/μl) were present in 51 patients (21%). Patients with hematological abnormalities showed higher SOFA scores, respiratory failure, septic shock and in-hospital mortality than the remaining patients. The composite endpoint was present in 33.3% in the cytopenias group vs. 13.3% in the group without cytopenias (p=0.001). In a multivariate analysis, variables associated with the composite endpoint were: use of steroids prior to present admission (OR: 0.12; 95% CI: 0.015–0.96, p=0.046), presence of any hematological abnormality (OR: 3.54; 95% CI:1.66–7.51, p= 0.001), and LDH>225 U/l (OR:4.45; CI:1–19.71, p=0.049). Hematological abnormalities are not uncommon among hospitalized patients with influenza virus infection, and they are associated with a poorer outcome.

Influenza virus infections in patients with malignancies \u2013\u2013 characteristics and outcome of the season 2014/15. A survey conducted by the Infectious Diseases Working Party (AGIHO) of the German Society of Haematology and Medical Oncology (DGHO)

Influenza virus infections (IVI) may pose a vital threat to immunocompromised patients such as those suffering from malignancies, but specific data on epidemiology and outcome in these patients are scarce. In this study, we collected data on patients with active cancer or with a history of cancer, presenting with documented IVI in eight centres in Germany. Two hundred and three patients were identified, suffering from haematological malignancies or solid tumours; 109 (54 %) patients had active malignant disease. Influenza A was detected in 155 (77 %) and Influenza B in 46 (23 %) of patients (genera not determined in two patients). Clinical symptoms were consistent with upper respiratory tract infection in 55/203 (27 %), influenza-like illness in 82/203 (40 %), and pneumonia in 67/203 (33 %). Anti-viral treatment with oseltamivir was received by 116/195 (59 %). Superinfections occurred in 37/203 (18 %), and admission on an intensive care unit was required in 26/203 (13 %). Seventeen patients (9 %) died. Independent risk factors for death were delayed diagnosis of IVI and bacterial or fungal superinfection, but not underlying malignancy or ongoing immunosuppression. In conclusion, patients with IVI show high rates of pneumonia and mortality. Early and rapid diagnosis is essential. The high rate of pneumonia and superinfections should be taken into account when managing IVI in these patients.

Current Approaches for Diagnosis of Influenza Virus Infections in Humans.

Despite significant advancement in vaccine and virus research, influenza continues to be a major public health concern. Each year in the United States of America, influenza viruses are responsible for seasonal epidemics resulting in over 200,000 hospitalizations and 30,000–50,000 deaths. Accurate and early diagnosis of influenza viral infections are critical for rapid initiation of antiviral therapy to reduce influenza related morbidity and mortality both during seasonal epidemics and pandemics. Several different approaches are currently available for diagnosis of influenza infections in humans. These include viral isolation in cell culture, immunofluorescence assays, nucleic acid amplification tests, immunochromatography-based rapid diagnostic tests, etc. Newer diagnostic approaches are being developed to overcome the limitations associated with some of the conventional detection methods. This review discusses diagnostic approaches currently available for detection of influenza viruses in humans.

Diagnostic Potential of Recombinant scFv Antibodies Generated Against Hemagglutinin Protein of Influenza A Virus

Human influenza A viruses have been the cause of enormous socio-economic losses worldwide. In order to combat such a notorious pathogen, hemagglutinin protein (HA) has been a preferred target for generation of neutralizing-antibodies as potent therapeutic/diagnostic agents. In the present study, recombinant anti-HA single chain variable fragment antibodies were constructed using the phage-display technology to aid in diagnosis and treatment of human influenza A virus infections. Spleen cells of mice hyper-immunized with A/New Caledonia/20/99 (H1N1) virus were used as the source for recombinant antibody (rAb) production. The antigen-binding phages were quantified after six rounds of bio-panning against A/New Caledonia/20/99 (H1N1), A/California/07/2009 (H1N1)-like, or A/Udorn/307/72(H3N2) viruses. The maximum phage yield was for the A/New Caledonia/20/99 (H1N1), however, considerable cross-reactivity was observed for the other virus strains as well. The HA-specific polyclonal rAb preparation was subjected to selection of single clones for identification of high reactive relatively conserved epitopes. The high-affinity rAbs were tested against certain known conserved HA epitopes by peptide ELISA. Three recombinant mAbs showed reactivity with both the H1N1 strains and one (C5) showed binding with all the three viral strains. The C5 antibody was thus used for development of an ELISA test for diagnosis of influenza virus infection. Based on the sample size in the current analysis, the ELISA test demonstrated 83.9% sensitivity and 100% specificity. Thus, the ELISA, developed in our study, may prove as a cheaper alternative to the presently used real time RT–PCR test for detection of human influenza A viruses in clinical specimens, which will be beneficial, especially in the developing countries.

Quantitative RT-PCR evaluation of a rapid influenza antigen test for efficient diagnosis of influenza virus infection

Influenza virus infection is diagnosed in most cases using a rapid influenza antigen diagnostic test (RIDT). However, false-negative results are a major concern. By contrast, the nucleic acid amplification test offers high sensitivity and therefore can aid the interpretation of negative RIDT results. In this study, influenza viral loads were quantified with quantitative reverse transcription-polymerase chain reaction (qRT-PCR) using viral suspensions left over after RIDT, and the performance of both methods was evaluated. qRT-PCR detected as few as 103copies/mL of influenza viruses A and B, whereas RIDT showed negative results for viral loads less than 107 and 105copies/mL of influenza viruses A and B, respectively. These results indicate that small quantities of the virus that cause false-negative RIDT results can be detected efficiently with qRT-PCR follow-up. In addition, influenza A virus subtype was determined using qRT-PCR.

Effect of the influenza virus rapid antigen test on a physician's decision to prescribe antibiotics and on patient length of stay in the emergency department.

BackgroundInfluenza virus infection is a common reason for visits to the emergency department (ED) during the influenza season. A rapid and accurate diagnosis of influenza virus infection is important to reduce unnecessary antibiotic prescription and to improve patient care. The aim of this study was to examine whether using the Influenza Virus Rapid Antigen Test (IVRAT) in the ED affects the decision to prescribe antibiotics or the length of hospital stay (LOS).MethodsData from patients suffering from an influenza-like illness (ILI) and who were discharged after visiting the ED at Chungbuk National University Hospital were reviewed over two influenza seasons: 2010–2011, when IVRAT was not used in the ED, and 2011–2012, when it was. The numbers of antibiotic prescriptions issued and the ED LOS during these two seasons were then compared.ResultsThe number of antibiotic prescriptions was significantly lower in 2011–2012 (54/216, 25.0%) than in 2010–2011 (97/221, 43.9%; P<0.01). However, the median ED LOS for patients in 2011–2012 was much longer than that of patients in 2010–2011 (213 minutes vs. 257 minutes; P<0.01). During the 2011–2012 influenza season, 73 ILI patients showed a positive IVRAT result whereas 123 showed a negative result. Upon discharge, antibiotics were given to 42/123 (34.1%) ILI patients with a negative IVRAT result, but to only 7/73 (9.6%) patients with a positive IVRAT result (P<0.01).ConclusionsPerforming IVRAT in the ED reduced the prescription of antibiotics to ILI patients discharged after ED care. However, the ED LOS for patients who underwent IVRAT was longer than that for patients who did not. Thus, performing IVRAT in the ED reduces the unnecessary prescription of antibiotics to ILI patients during the influenza season.

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

Five years ago, the Point-Counterpoint series was launched. The initial article asked about the role of rapid immunochromatographic antigen testing in the diagnosis of influenza A virus 2009 H1N1 infection (D. F. Welch and C. C. Ginocchio, J Clin Microbiol 48:22-25, 2010, http://dx.doi.org/10.1128/JCM.02268-09). Since that article, not only have major changes been made in immunochromatographic antigen detection (IAD) testing for the influenza viruses, but there has also been rapid development of commercially available nucleic acid amplification tests (NAATs) for influenza virus detection. Further, a novel variant of influenza A, H7N9, has emerged in Asia, and H5N1 is also reemergent. In that initial article, the editor of this series, Peter Gilligan, identified two issues that required further consideration. One was how well IAD tests worked in clinical settings, especially in times of antigen drift and shift. The other was the role of future iterations of influenza NAATs and whether this testing would be available in a community hospital setting. James Dunn, who is Director of Medical Microbiology and Virology at Texas Children's Hospital, has extensive experience using IAD tests for diagnosing influenza. He will discuss the application and value of these tests in influenza diagnosis. Christine Ginocchio, who recently retired as the Senior Medical Director, Division of Infectious Disease Diagnostics, North Shore-LIJ Health System, and now is Vice President for Global Microbiology Affairs at bioMérieux, Durham, NC, wrote the initial counterpoint in this series, where she advocated the use of NAATs for influenza diagnosis. She will update us on the commercially available NAAT systems and explain what their role should be in the diagnosis of influenza infection.