Comparison of the NOW Influenza A & B, NOW Flu A, NOW Flu B, and Directigen Flu A+B assays, and immunofluorescence with viral culture for the detection of influenza A and B viruses

To evaluate the Binax NOW Influenza A & B combination assay, we tested upper respiratory tract samples in parallel with the Binax NOW Flu A and Binax NOW Flu B assays, the Becton-Dickinson Directigen Flu A+B assay, and immunofluorescence, and the results were compared with viral culture. Of the 521 samples tested, influenza A was cultured from 113 and influenza B from 6. There were no significant differences in the performance of all rapid antigen tests, with sensitivities of 53% to 59% for detecting influenza A compared with culture and immunofluorescence (80%). The sensitivities for all rapid tests were significantly higher for nasopharyngeal samples than for throat swabs. The Binax NOW Influenza A & B assay performed as well as other rapid assays. Commercial antigen detection assays are useful tools for the rapid diagnosis of influenza; however, confirmatory testing is always recommended. The use of nasopharyngeal samples for all rapid detection methods should be strongly encouraged.     

Evaluation of the limit of detection of the BD Veritor™ system flu A+B test and two rapid influenza detection tests for influenza virus

We evaluated the limits of detection of 3 rapid influenza diagnostic tests—BD Veritor^TM System for Flu A+B, Binax NOW® Influenza A+B, and QuickVue® Influenza—for influenza strains circulating in 2010–2012. Limits of detection varied by influenza strain, with Veritor^TM Flu A+B test showing the lowest limit of detection for all strains.     

流感病毒快速检测法在北京地区2007-2008年流感季节中的应用

目的 分析评价采用流感病毒快速检测法诊治流感的应用价值.方法 前瞻性选择2007年12月-2008年3月流感季节在北京朝阳医院发热门诊就诊的符合卫生部流感样病例患者500例,留取咽部分泌物进行流感病毒培养,随机选取260例患者进行流感病毒快速检测,并调查患者性别、年龄、症状、实验室检查、症状恢复时间、治疗花费等因素.同时分析流感病毒培养阳性组与流感病毒快速检测组的敏感度、特异度、阳性预测值和阴性预测值,及对治疗方案和预后的影响.结果 2007-2008年流感季节共入选流感样病例500例,最终498例纳入分析,病毒培养结果主要为乙型流感(208例,41.8%),而甲型流感少见(51例,10.2%).498例流感样患者的平均年龄为35岁,男:女比例为1.47:1.与培养阴性组比较,培养阳性组咳嗽、咽痛、鼻塞症状比例比较高(t值分别为13.728、4.014和4.720,P均<0.01或0.05).260例经流感病毒快速检测患者中,甲型流感抗原阳性18例、乙型流感抗原阳性132例,流感病毒快速检测的敏感度77.1%、特异度70.1%、阳性预测值78.6%、阴性预测值68.2%.流感病毒快速检测抗病毒治疗的比例由0提高到26%,抗生素使用比例由63.4%降到20.7%.结论 2007-2008年流感季节主要流感类型为乙型流感,流感病毒快速检测法对临床病例检测敏感度和特异度较高,对临床抗病毒诊治有指导意义.     

Influenza B: hospital activity during a community epidemic

During a community epidemic of influenza B, surveillance throat cultures for influenza were collected from febrile adult patients and hospital employees on three medical wards to determine the frequency and source of influenza among hospitalized patients. Twenty-five cases of influenza B (18.5% of febrile patients) were identified; no clusters of influenza-like illness occurred. The attack rate on two wards was 4.6%. Peak hospital influenza incidence followed that in the community by 1-2 weeks. Twelve of the cases were community-acquired and 13 were nosocomial. 75% of community-acquired cases had three or more common influenza B symptoms, compared with only 39% of nosocomial cases. A viral etiology of fever was suspected clinically in one-half of the cases, but influenza was specifically suspected in only one case. Two ill culture-positive nurses were identified on the job but no asymptomatic carriers were found among ward personnel. We conclude that influenza B cases were present among hospitalized patients in the absence of recognizable clusters of disease and that patients with community-acquired illness as well as nursing personnel may have introduced influenza into the hospital. Influenza B may be difficult to diagnose clinically in hospitalized patients, but viral throat cultures performed in all suspected cases should identify many infected patients.     

免疫荧光分析法在快速诊断 A、B 型流感病毒中的临床应用

目的：探讨 Sofia Influenza A＋B FIA 检测系统在快速诊断 A、B 型流感病毒中的临床应用价值。方法获取临床168例流感患儿的鼻咽拭子样本,分别通过 Sofia Influenza A＋B FIA 检测系统和胶体金免疫层析（GICA）法分别进行 A、B 型流感病毒检测,并通过逆转录聚合酶链反应（RT-PCR）进行验证。结果Sofia Influenza A ＋B FIA 检测系统的阳性检出率为17．86％（30/168）,高于 GICA 法;同时,与 RT-PCR 相比,对 A 型流感病毒和 B 型流感病毒的灵敏度分别达到83．3％和71．4％,特异性均达到100．0％。结论Sofia Influenza A＋B FIA 检测系统是一种灵敏度和特异性均较高,能够快速检测 A、B 型流感病毒的方法。     

Evaluation of the molecular Xpert Xpress Flu/RSV assay vs. Alere i Influenza A & B assay for rapid detection of influenza viruses

A new FDA-approved Xpert Xpress Flu/RSV assay has been released for rapid influenza virus detection. We collected 134 nasopharyngeal specimens to compare the diagnostic performance of the Xpert assay and the Alere i Influenza A & B assay for influenza A and B virus detection. The Xpert assay demonstrated 100% and 96.3% sensitivity to influenza A and influenza B virus respectively. Its specificity was 100% for both viruses. The Alere i assay demonstrated slightly lower sensitivity but similar specificity to the Xpert Xpress assay. Although the Xpert assay (30 min) required longer processing time than the Alere assay (15 min), the handling procedure of the Alere assay was more complicated than the Xpert assay. As the GenXpert system has higher throughput than the Alere system, it is more suitable for hospital clinical laboratories. Overall, the new Xpert Xpress Flu/RSV assay is a reliable and useful tool for rapid influenza detection.     

The rapid detection kit based on neuraminidase activity of influenza virus

The ZstatFlu test(ZymeTx, USA) is a rapid detection kit for influenza types A and B virus. This test is based upon the reaction between viral neuraminidase from influenza viruses and chromogenic substrate. The positive specimen of influenza type A or B virus cleave the substrate and produce a blue colored product. The ZstatFlu was evaluated by a prototype viruses, isolated viruses and clinical specimens. At result, this kit was reactive for all human influenza type A and B virus. No cross reactivity was detected with other respiratory viruses, including parainfluenza type 1, 2, 3 and mumps viruses with neuraminidase activity. Throat swabs were used for the test. By comparison with cell culture and RT-PCR. The sensitivity and the specificity was 77.0% and 90.2% respectively. The ZstatFlu should be useful for the rapid diagnosis of influenza virus infection.     

Influenza vaccine effectiveness in primary school children in Japan: a prospective cohort study using rapid diagnostic test results

A low-cost, prospective cohort study using the results of rapid diagnostic test performed at local clinics was conducted to estimate influenza vaccine effectiveness (VE) in school children (6–12 year-olds). All children in four primary schools in Tsuchiura City, Ibaraki, Japan were enrolled (n = 2607). Vaccination status and other risk factors were obtained with a baseline questionnaire. Participants were encouraged to visit a clinic to have a rapid test when they developed an influenza-like illness during the winter season in 2006–2007, and 88.6% of those who reported influenza to the school had been tested. The result of the test was obtained with another questionnaire. The attack rate of influenza A and B was 5.4% and 11.9%, respectively. Logistic regression was used to model the association between influenza vaccination and rapid-test-confirmed influenza after adjusting for potential confounders. Influenza VE was calculated as (1– adjusted odds ratio) × 100. VE for total influenza was 21% (95% confidence interval −8 to 42), which was a combination of VE for influenza A (44%, 8–66) and VE for influenza B (5%, −37 to 34). Among several possibilities that would account for rather low VE estimates in this study, low sensitivity of the rapid test, and differential propensity to seek vaccination or medical care between the vaccinated and nonvaccinated were considered to be important. This study was able to estimate influenza VE at very low cost with high specificity in case ascertainment by collecting the readily available data on influenza rapid test with questionnaires.     

Influenza A Subtyping: Seasonal H1N1, H3N2, and the Appearance of Novel H1N1

Influenza virus subtyping has emerged as a critical tool in the diagnosis of influenza. Antiviral resistance is present in the majority of seasonal H1N1 influenza A infections, with association of viral strain type and antiviral resistance. Influenza A virus subtypes can be reliably distinguished by examining conserved sequences in the matrix protein gene. We describe our experience with an assay for influenza A subtyping based on matrix gene sequences. Viral RNA was prepared from nasopharyngeal swab samples, and real-time RT-PCR detection of influenza A and B was performed using a laboratory developed analyte-specific reagent-based assay that targets a conserved region of the influenza A matrix protein gene. FluA-positive samples were analyzed using a second RT-PCR assay targeting the matrix protein gene to distinguish seasonal influenza subtypes based on differential melting of fluorescence resonance energy transfer probes. The novel H1N1 influenza strain responsible for the 2009 pandemic showed a melting profile distinct from that of seasonal H1N1 or H3N2 and compatible with the predicted melting temperature based on the published novel H1N1 matrix gene sequence. Validation by comparison with the Centers for Disease Control and Prevention real-time RT-PCR for swine influenza A (novel H1N1) test showed this assay to be both rapid and reliable (>99% sensitive and specific) in the identification of the novel H1N1 influenza A virus strain.The 2009 novel influenza A/H1N1 viral pandemic has presented challenges for hospital laboratories and health care systems seeking to rapidly diagnose, treat, and limit the spread of this virus. As is the case for routine diagnosis of seasonal influenza infections, molecular amplification assays offer the potential for the sensitivity and speed needed to manage an influenza outbreak. However, standardized RT-PCR assays specific for this strain of influenza were not initially available, leaving many laboratories to diagnose this infection through indirect means.Our laboratory has used PCR for rapid detection of influenza A and B for several years, and more recently had implemented a rapid RT-PCR/melt-curve assay designed to differentiate seasonal influenza A subtypes H1N1 and H3N2.¹ This approach was initially developed for viral subtyping to guide clinicians on the appropriate antiviral therapy. Antiviral resistance has risen during recent years, with the majority of seasonal H1N1 strains no longer being sensitive to oseltamivir (Tamiflu), and seasonal H3N2 strains being largely resistant to adamantanes.² Rapid determination of influenza A subtype is essential for determining optimal therapy and for prudent use of antiviral agents. Consequently, this RT-PCR assay has become part of our influenza testing algorithm.The design of the RT-PCR assay exploits minor variations in a relatively conserved sequence within the matrix protein gene. Not surprisingly, the novel H1N1 strain of influenza that appeared in the spring of 2009 had a distinct melting temperature consistent with the published matrix gene sequence and the sequence of the fluorescence resonance energy transfer probes used in this assay designed to differentiate seasonal influenza A subtypes H1N1 and H3N2. As part of our influenza testing algorithm, this assay allowed definitive diagnosis of the 2009 influenza H1N1 from nasopharyngeal swabs within hours after arrival in the clinical laboratory.     

Profile of the Alere i Influenza A & B assay: a pioneering molecular point-of-care test

Introduction: The Alere i Influenza A & B assay incorporates the Nicking Enzyme Amplification Reaction technique on the Alere i instrument to detect and differentiate influenza virus (Flu) A and B nucleic acids in specific specimens.

Areas covered: The Alere i Influenza A & B assay was cleared by the US Food and Drug Administration for use with nasal swabs (NS) and nasopharyngeal swabs, either directly or in viral transport medium. Notably, direct use on NS was the first ever CLIA-waived nucleic acid-based test. Previously published evaluations have reported sensitivities and specificities of 55.2–100% and 62.5–100% for Flu A and 45.2–100% and 53.6–100% for Flu B, respectively.

Expert commentary: The Alere i Influenza A & B assay provides a rapid and simple platform for detection and differentiation of Flu A and B. Efforts are expected to further improve sensitivity and user-friendliness for effective and widespread use in the true point-of-care setting.     

Influenza viral load and rapid influenza diagnostic tests in children and adults

We compared children and adults with regard to rapid influenza test sensitivity and viral load. Specimen volumes were measured, rapid tests were conducted, and viral load was determined. There was no difference between children and adults in test sensitivity or viral load, but children had higher specimen volumes.     

Comparison of BinaxNOW Influenza A&B assay and real-time reverse transcription polymerase chain reaction for diagnosis of influenza A pandemic (H1N1) 2009 virus infection in adult patients

The BinaxNOW Influenza A&;B assay was evaluated for the diagnosis of influenza A pandemic (H1N1) 2009 virus infection in 354 adult patients. The sensitivity, specificity, and positive and negative predictive values were 32%, 100%, 100%, and 67%, respectively. The analytic sensitivity of the assay was log₁₀ 5.0 tissue culture infective dose (TCID)₅₀/mL.     

Sensitivity of a marketed immunochromatographic assay specifically targeting the pandemic influenza A/H1N1 2009 virus

The sensitivity of an immunochromatographic assay specifically detecting the pandemic influenza A/H1N1 2009 virus (influenza Ag A/B/A(H1N1) pandemic rapid test; SD Standard Diagnostics, South Korea) was evaluated. The overall sensitivity of the assay and its analytic sensitivity were 26.9% and 2.6 × 10⁴ TCID₅₀/mL, respectively.     

甲型流感病毒抗原及核酸检测联合应用研究

目的:通过大样本流感样病例检测,明确抗原检测与核酸检测两种方法联合应用原则,从而快速明确流感诊断,控制流感暴发,减少资源浪费。方法:采集2019年1月至2020年1月北京同仁医院发热门诊的4 622份流感样病例咽拭子标本,其中流感季3 230份,非流感季1 392份,采用快速抗原法和实时荧光逆转录聚合酶链反应（qPCR...