Analytical and clinical sensitivity of the 3M rapid detection influenza A+B assay

A narrative review of nine commercial point of care influenza tests: an overview of methods, benefits, and drawbacks to rapid influenza diagnostic testing

CONTEXT

Rapid influenza diagnostic tests (RIDTs) are becoming increasingly accurate, available, and reliable as the first line of testing when suspecting influenza infections, although the global burden of influenza infections remains high. Rapid diagnosis of influenza infections has been shown to reduce improper or delayed treatment and to increase access to diagnostic measures in public health, primary care, and hospital-based settings.

OBJECTIVES

As the use of RIDTs continues to expand in all healthcare settings, there is a multitude of molecular techniques being employed by these various testing platforms. With this in mind, we compare the sensitivity, specificity, and time to diagnosis for nine highly utilized commercial RIDTs.

METHODS

Nine commercially available RIDTs were identified from the US Centers for Disease Control and Prevention (CDC) website, which were also referenced on PubMed by name within the title or abstract of peer-reviewed publications examining the sensitivity and specificity of each test against a minimum of three influenza A virus (IAV) strains as well as seasonal influenza B virus (IBV). Data from the peer-reviewed publications and manufacturers' websites were combined to discuss the sensitivity, specify, and time to diagnosis associated with each RIDT.

RESULTS

The sensitivity and specificity across the examined RIDTs were greater than 85.0% for both IAV and IBV across all platforms, with the reverse transcriptase-polymerase chain reaction (RT-PCR) assays maintaining sensitivity and specificity greater than 95.0% for all viruses tested. However, the RT-PCR platforms were the longest in time to diagnosis when compared to the other molecular methods utilized in the examined RIDTs.

CONCLUSIONS

Herein, we discussed the benefits and limitations of nine commercially available RIDTs and the molecular techniques upon which they are based, showing the relative accuracy and speed of each test for IAV and IBV detection as reported by the peer-reviewed literature and commercial manufacturers.

Diagnostic accuracy and cost analysis of the Alere™ i Influenza A&B near-patient test using throat swabs

BACKGROUND

Clinical diagnostic sensitivity alone is inadequate in the diagnosis of influenza. Polymerase chain reaction (PCR) testing is sensitive but the inherent delays in result availability potentially prolong time to isolation and treatment. Until recently no near-patient test (NPT) has demonstrated adequate sensitivity for routine clinical use.

AIM

To evaluate diagnostic accuracy, time to result availability, clinical impact, and cost consequences of Alere™ i Influenza A&B NPT (Alere Inc., Waltham, MA, USA) using off-label throat swabs.

METHODS

Prospective, multi-centre [four UK National Health Service (NHS) hospitals], diagnostic accuracy cohort study with cost modelling. Throat swab samples from suspected influenza patients were tested for influenza using the reference standard of PCR; a second throat swab was tested using NPT.

FINDINGS

A total of 827 participants were recruited; 589 were suitable for analysis: sensitivity was 75.8% [95% confidence interval (CI): 67.0-84.6]; specificity was 96.8% (95% CI: 95.2-98.3). Sensitivity varied between Sheffield (Northern General Hospital: 82.1%; Royal Hallamshire Hospital: 83.3%) and other sites (Doncaster Royal Infirmary: 71.4%; Newcastle's Royal Victoria Infirmary: 50.0%) whereas specificity was high (92-100%). Positive predictive value (PPV) was 81.2% (95% CI: 72.9-89.5) with negative predictive value 95.6% (95% CI: 93.9-97.4) with observed prevalence of 15.4%. Median time to result for PCR was 1.1 days (on-site laboratories) and 5.2 days (remote laboratories). Isolation findings: 75% influenza positive not isolated; 69% of isolated participants did not have influenza. For a cohort of 1000 participants, annual estimated non-diagnostic cost savings with NPT are £215,040.

CONCLUSION

This first prospective study of the Alere i NPT using throat swabs demonstrates high specificity, high PPV during seasonal epidemics, and rapid result availability which could lead to substantial cost savings.

Rapid Molecular Detection and Differentiation of Influenza Viruses A and B

Influenza is a contagious respiratory illness caused by influenza viruses A and B in humans and causes a significant amount of morbidity and mortality every year. The Influenza A and B assay was the first CLIA-waived molecular rapid flu test available. The Influenza A and B test works by employing isothermal amplification with influenza-specific primers followed by target detection with molecular beacon probes. Here, the performance of the Influenza A and B assay on frozen, archived nasopharyngeal swab (NPS) specimens stored in viral transport medium (VTM) were compared to a respiratory panel assay. The performance of the Influenza A and B assay was evaluated by comparing the results to the respiratory panel reference method. The sensitivity for total influenza virus A was 67.5% (95% CI (CI), 56.6-78.5) and the specificity was 86.9% (CI, 71.0-100). For influenza virus B testing, the sensitivity and specificity were 90.2% (CI, 68.5-100) and 98.8% (CI, 68.5-100), respectively. This system has the advantage of a significantly shorter test time than any other currently available molecular assay and the simple, pipette-free procedure runs on a fully integrated, closed, small-footprint system. Overall, the Influenza A and B assay evaluated in this study has the potential to serve as a point-of-care rapid influenza diagnostic test.

Comparison of two new generation influenza rapid diagnostic tests with instrument-based digital readout systems for influenza virus detection

INTRODUCTION

Influenza rapid diagnostic tests (RDTs) have been developed to supply scientists with more sensitive and specific techniques. Newly developed digital reader-based techniques require test evaluations before their clinical application.

METHODS

Two types of digital influenza RDTs using a digital readout system and one conventional RDT were compared using 314 nasopharyngeal swabs of influenza. The swabs originated from symptomatic individuals suspected of influenza infection, and the presence of influenza was confirmed with influenza real-time polymerase chain reaction (PCR) testing and influenza subtyping. Methods were the Sofia® Influenza A + B Fluorescence Immunoassay (FIA), which uses a portable fluorescence analyser, the BD Veritor™ System Flu A + B, which uses a colorimetric immunochromatographic method with a reflectance-based measurement digital device, and the SD Bioline assay, which is based on a traditional immunochromatographic method.

RESULTS

The Sofia® Influenza A + B system, the BD Veritor™ System Flu A + B and the SD Bioline assay showed sensitivities in relative real-time PCR results of 74.2, 73.0 and 53.9%, respectively, for influenza A, and 82.5, 72.8 and 71.0%, respectively, for influenza B. All three RDTs showed 100% specificities for influenza A and influenza B. The Sofia® Influenza A + B Fluorescence Immunoassay showed sensitive and specific results for the detection of influenza B in contrast to the BD Veritor™ System Flu A + B. The two digital RDTs showed higher sensitivity and specificity than the conventional RDT in the detection of the influenza H3 subtype.

CONCLUSIONS

Digital-based readout systems for the detection of the influenza virus can be applied for more sensitive diagnosis in clinical settings than conventional RDTs.

Comparison of Directigen Flu A+B with Real Time PCR in the Diagnosis of Influenza

Early diagnosis and treatment of patients with influenza is the reason why physicians need rapid high-sensitivity influenza diagnostic tests that require no complex lab equipment and can be performed and interpreted within 15 min. The Aim of this study was to compare the rapid Directigen Flu A+B test with real time PCR for detection of influenza viruses in the Republic of Macedonia.

MATERIALS AND METHODS

One-hundred-eight respiratory samples (combined nose and throat swabs) were routinely collected for detection of influenza virus during influenza seasons. Forty-one patients were pediatric cases and 59 were adult. Their mean age was 23 years. The patients were allocated into 6 age groups: 0-4 yrs, 5-9 yrs, 10-14 yrs, 15-19 yrs, 20-64 yrs and > 65 yrs. Each sample was tested with Directigen Flu A+B and CDC real time PCR kit for detection and typisation/subtypisation of influenza according to the lab diagnostic protocol.

RESULTS

Directigen Flu A+B identified influenza A virus in 20 (18.5%) samples and influenza B virus in two 2 (1.9%) samples. The high specificity (100%) and PPV of Directigen Flu A+B we found in our study shows that the positive results do not need to be confirmed. The overall sensitivity of Directigen Flu A+B is 35.1% for influenza A virus and 33.0% for influenza B virus. The sensitivity for influenza A is higher among children hospitalized (45.0%) and outpatients (40.0%) versus adults.

CONCLUSION

Directigen Flu A+B has relatively low sensitivity for detection of influenza viruses in combined nose and throat swabs. Negative results must be confirmed.

Performance of the Cobas(®) Influenza A/B Assay for Rapid Pcr-Based Detection of Influenza Compared to Prodesse ProFlu+ and Viral Culture

Rapid and accurate diagnosis of influenza is important for patient management and infection control. We determined the performance of the cobas^® Influenza A/B assay, a rapid automated nucleic acid assay performed on the cobas^® Liat System for qualitative detection of influenza A and influenza B from nasopharyngeal (NP) swab specimens. Retrospective frozen and prospectively collected NP swabs from patients with signs and symptoms of influenza collected in universal transport medium (UTM) were tested at multiple sites including CLIA-waived sites using the cobas® Influenza A/B assay. Results were compared to the Prodesse Pro-Flu+ assay and to viral culture. Compared to the Prodesse ProFlu+ Assay, sensitivities of the cobas^® Influenza A/B assay for influenza A and B were 97.7 and 98.6%, respectively; specificity was 99.2 and 99.4%. Compared to viral culture, the cobas^® Influenza A/B assay showed sensitivities of 97.5 and 96.9% for influenza virus A and B, respectively; specificities were 97.9% for both viruses. Polymerase chain reaction (PCR)/sequencing showed that the majority of viral culture negative but cobas^® Influenza A/B positive results were true positive results, indicating that the cobas^® Influenza A/B assay has higher sensitivity compared to viral culture.

In conclusion, the excellent accuracy, rapid time to result, and remarkable ease of use make the cobas^® Influenza A/B nucleic acid assay for use on the cobas^® Liat System a highly suitable point-of-care solution for the management of patients with suspected influenza A and B infection.

Evaluation of Alere i Influenza A&B for rapid detection of influenza viruses A and B

Rapid and accurate diagnosis of influenza is important for infection control, as well as for patient management. Alere i Influenza A&B is an isothermal nucleic acid amplification-based integrated system for detection and differentiation of influenza virus A and influenza virus B. The performance of the Alere i Influenza A&B was screened using frozen nasopharyngeal-swab specimens collected in viral transport medium (VTM) that were originally tested fresh with the FilmArray Respiratory Panel (RP) assay during the 2012-2013 influenza outbreak. In total, 360 VTM specimens were selected for Alere i Influenza A&B testing: 40 influenza virus A H1N1-2009 (influenza virus A-1), 40 influenza virus A H3N2 (influenza virus A-3), 37 influenza virus A "equivocal" or "no subtype detected" (influenza virus A-u), 41 influenza virus B, and 202 influenza virus-negative specimens, as initially determined by the FilmArray RP assay. The Alere assay showed sensitivities of 87.2%, 92.5%, 25.0%, and 97.4% for influenza virus A-1, influenza virus A-3, influenza virus A-u, and influenza virus B, respectively, after discordant resolution by Prodesse ProFLU+ PCR. The specificities were 100% for both influenza virus A and influenza virus B. In general, the Alere i Influenza A&B provided good sensitivity, although the assay did show poorer sensitivity with samples determined to have low influenza virus A titers by Prodesse ProFlu+ PCR (a mean real-time PCR threshold cycle [CT] value of 31.9 ± 2.0), which included the majority of the samples called influenza virus A "equivocal" or "no subtype detected" by a single BioFire FilmArray RP test. The integrated, rapid, and simple characteristics of the Alere i Influenza A&B assay make it a potential candidate for point-of-care testing, with a test turnaround time of less than 15 min.

Clinical performance evaluation of the BD Veritor System Flu A+B assay

Early identification of influenza is important for optimal patient management and infection control. Rapid influenza antigen tests have been used routinely in clinical settings to confirm clinical suspicion, despite their low sensitivity. To improve sensitivity, various influenza point-of-care test reader systems have been developed. This study evaluated the clinical performance of a digital readout rapid influenza diagnostic test (RIDT), the BD Veritor™ System Flu A+B assay (BD). Nasopharyngeal swabs taken from 250 patients (influenza A positive, n=75; influenza B positive, n=75; and influenza negative, n=100) were analyzed using the BinaxNOW® Influenza A/B antigen kit (BN), SD Influenza Ag A/B kit (SD), BD, real-time reverse transcriptase polymerase chain reaction (RT-PCR), and an influenza virus culture. Compared to RT-PCR, the sensitivities of BN, SD, and BD were 56.0, 53.3, and 72.0%, respectively, for influenza A and 57.3, 65.3, and 69.3%, respectively, for influenza B. No false-positive results were noted with the three rapid antigen tests. For influenza A, the average RT-PCR threshold cycle (Ct) for specimens that tested positive using BD was higher than that for specimens that tested positive using BN and SD. BD is a sensitive and easy method for the early detection of influenza A and B.

Evaluation of five rapid diagnostic kits for influenza A/B virus

Influenza viruses cause seasonal epidemics associated with high morbidity and mortality. However, even during periods of epidemic prevalence, clinical diagnoses are problematic. Rapid diagnostic tests for the detection of pandemic influenza A/B virus are valuable for their ease of use. Many rapid influenza diagnostic kits were introduced recently in the Republic of Korea (ROK), including Directizen EZ Flu A and B (Becton Dickinson, Sparks, USA), Binax Now Influenza A/B antigen kit (Binax, Portland, USA), Genedia influenza Ag (Green Cross, Yongin, ROK), Humasis Influenza A/B antigen test (Humasis, Anyang, ROK), and SD Bioline rapid influenza kit (Standard Diagnostics, Yongin, ROK). The objective of this study was to evaluate the performance of these five rapid diagnostic kits. The results were compared with those of viral culture and reverse transcription (RT)-PCR. A total of 253 nasopharyngeal swabs were analyzed from 253 patients (influenza A, n=67; B, n=86; negative samples, n=100). The specimens were tested immediately by conventional influenza virus culture and RT-PCR, stored at -80°C, and tested using five rapid test kits. The performance of the five rapid tests kits varied with sensitivities between 71.0 and 82.1% and between 37.2 and 47.7% for detecting influenza A and B, respectively. For influenza A, the sensitivities of the Directizen EZ Flu A and B, Binax Now Influenza A/B antigen kit, Genedia influenza Ag, Humasis Influenza A/B antigen test, and SD Bioline rapid influenza kits were 82.1%, 71.0%, 76.1%, 79.1%, and 82.1%, respectively; those for influenza B were 40.7%, 37.2%, 40.7%, 41.8%, and 47.7%, respectively. The specificity of all rapid tests was 100%. Commercial influenza antigen detection assays are useful tools for the rapid diagnosis of influenza. However, confirmatory testing is always recommended.

Update on influenza diagnostics: lessons from the novel H1N1 influenza A pandemic

The menu of diagnostic tools that can be utilized to establish a diagnosis of influenza is extensive and includes classic virology techniques as well as new and emerging methods. This review of how the various existing diagnostic methods have been utilized, first in the context of a rapidly evolving outbreak of novel influenza virus and then during the different subsequent phases and waves of the pandemic, demonstrates the unique roles, advantages, and limitations of each of these methods. Rapid antigen tests were used extensively throughout the pandemic. Recognition of the low negative predictive values of these tests is important. Private laboratories with preexisting expertise, infrastructure, and resources for rapid development, validation, and implementation of laboratory-developed assays played an unprecedented role in helping to meet the diagnostic demands during the pandemic. FDA-cleared assays remain an important element of the diagnostic armamentarium during a pandemic, and a process must be developed with the FDA to allow manufacturers to modify these assays for detection of novel strains in a timely fashion. The need and role for subtyping of influenza viruses and antiviral susceptibility testing will likely depend on qualitative (circulating subtypes and their resistance patterns) and quantitative (relative prevalence) characterization of influenza viruses circulating during future epidemics and pandemics.

Diagnosis of influenza from respiratory autopsy tissues: detection of virus by real-time reverse transcription-PCR in 222 cases

The recent influenza pandemic, caused by a novel H1N1 influenza A virus, as well as the seasonal influenza outbreaks caused by varieties of influenza A and B viruses, are responsible for hundreds of thousands of deaths worldwide. Few studies have evaluated the utility of real-time reverse transcription-PCR to detect influenza virus RNA from formalin-fixed, paraffin-embedded tissues obtained at autopsy. In this work, respiratory autopsy tissues from 442 suspect influenza cases were tested by real-time reverse transcription-PCR for seasonal influenza A and B and 2009 pandemic influenza A (H1N1) viruses and the results were compared to those obtained by immunohistochemistry. In total, 222 cases were positive by real-time reverse transcription-PCR, and of 218 real-time, reverse transcription-PCR-positive cases also tested by immunohistochemistry, only 107 were positive. Although formalin-fixed, paraffin-embedded tissues can be used for diagnosis, frozen tissues offer the best chance to make a postmortem diagnosis of influenza because these tissues possess nucleic acids that are less degraded and, as a consequence, provide longer sequence information than that obtained from fixed tissues. We also determined that testing of all available respiratory tissues is critical for optimal detection of influenza virus in postmortem tissues.

Clinical performance of three rapid diagnostic tests for influenza virus in nasopharyngeal specimens to detect novel swine-origin influenza viruses

BACKGROUND

Influenza is an important public health problem. The aim of this study was to evaluate and compare the sensitivity and specificity of three rapid diagnostic tests (SEKISUI, QuickVue Influenza A + B, and SD BIOLINE) for novel swine-origin influenza viruses (S-OIV) and seasonal influenza.

MATERIALS AND METHODS

A total of 210 nasopharyngeal swabs from unique clinical specimens were previously tested by real-time reverse transcription polymerase chain reaction (RT-PCR) assay and tested again in this study.

RESULTS AND DISCUSSION

Of these, 164 (78%) were influenza A-positive and 46 (22%) were influenza A-negative by RT-PCR. From 115 positive swabs, 80 (69.6%), 66 (57.4%), and 46 (40.0%) showed S-OIV by SEKISUI, QuickVue Influenza A + B, and SD BIOLINE, respectively. Specific positive and negative predictive values of these three commercial rapid tests were all 100%. Therefore, positive rapid influenza virus diagnosis does not require an RT-PCR confirmatory test. Conversely, only negative rapid influenza virus diagnosis should be evaluated. The SEKISUI test would be a useful diagnostic tool for screening clinical samples for influenza. Concerning the various specimen types, among 25 patients with RT-PCR-proven S-OIV infection, influenza was identified in sputum (21/25; 84.0%) and nasopharyngeal swab (15/25; 60.0%) specimens, but in only 36.0% (9/25) of throat swab specimens. Sputum and nasopharyngeal swab specimens were the most predictive of influenza virus infection, while throat swab specimens were the least predictive of influenza virus infection.

Diagnostic tests for influenza infection

PURPOSE OF REVIEW

The 2009 H1N1 pandemic focused attention on the speed and accuracy of influenza diagnostic methods. This review provides an update on current tests and new developments.

RECENT FINDINGS

Widely used rapid antigen tests and immunofluorescence tests were generally less sensitive for 2009 H1N1 influenza than for seasonal influenza. In addition, marked variability was reported for the same tests in different settings and patient groups. The advantages of molecular testing gained wide recognition, namely high sensitivity, speed compared with culture, ability to assess viral load and to identify subtype. Although adoption of influenza molecular testing can be expected to accelerate, immunoassays and rapid cultures performed on site retain advantages for many facilities. Falsely negative results were seen with all methods, especially for samples collected very early or late.

SUMMARY

Influenza diagnostic test performance can be adversely affected by viral genetic and antigenic changes and should be re-assessed annually. Variability in sensitivity and specificity of the same test in different settings highlights the need for each laboratory to ensure optimal procedures and work with clinicians to improve sample quality. Manufacturers have been motivated to improve immunoassays and develop simpler and faster multiplex molecular tests, hopefully in advance of the next pandemic.

Developments in immunologic assays for respiratory viruses

In most hospitals, clinics, and doctor's offices, immunologic assays are the only tests performed on site for the diagnosis of respiratory viruses. More than other methods, immunoassays have been shown to affect patient management and save costs, aiding early administration of antiviral therapy, reduction in unnecessary tests and antibiotics, and earlier discharges. This article discusses the major immunologic methods employed for respiratory virus diagnosis, recent developments in immunoassays and sample collection, and current test algorithms.

Clinical performance of the 3M Rapid Detection Flu A+B Test compared to R-Mix culture, DFA and BinaxNOW Influenza A&B Test

BACKGROUND

The rapid diagnosis of influenza allows for prompt patient management and the initiation of appropriate infection control measures to reduce spread in healthcare settings.

OBJECTIVE

To evaluate the clinical performance of the 3M Rapid Detection Flu A+B Test (3MA+B) as compared to R-Mix cell culture, direct immunofluorescence assay (DFA) and the BinaxNOW A&B Influenza Test (BinaxNOW).

STUDY DESIGN

Five hundred fresh respiratory samples, collected from patients aged 5 days to 99 years with respiratory symptoms, were tested by R-Mix culture, DFA, 3MA+B and BinaxNOW. Analytical sensitivity of 3MA+B was compared to BinaxNOW using replicates of serially diluted clinical samples positive for influenza A or B.

RESULTS

Sensitivity, specificity, PPV and NPV for the detection of influenza A and B, respectively, were for R-Mix (96.9%, 100%, 100%, 99.3%; 98.1%, 100%, 100%, 99.8%), DFA (80.4%, 99.2%, 96.1%, 95.3%; 74%, 100%, 100%, 97%), 3MA+B (70.1%, 99.8%, 98.6%, 93%; 86.5%, 98.7%, 88.2%, 98.4%) and BinaxNOW (46.4%, 100%, 100%, 88.6%; 34.6%, 100%, 100%, 93%). R-Mix, DFA and 3MA+B were significantly (P<or=0.0001) more sensitive than BinaxNOW for the detection of both influenza A and B. The analytical sensitivity of 3MA+B was greater than BinaxNOW. Excessive blood in samples may cause 3MA+B false positive influenza B results.

CONCLUSIONS

The 3MA+B provided superior results compared to BinaxNOW. The 3MA+B Reader eliminated user misinterpretation and provided quality control and result documentation. The improved sensitivity and easy of use makes 3MA+B an effective first line triage test for emergency departments, clinics and rapid response laboratories.

Seasonal influenza in adults and children--diagnosis, treatment, chemoprophylaxis, and institutional outbreak management: clinical practice guidelines of the Infectious Diseases Society of America

Guidelines for the treatment of persons with influenza virus infection were prepared by an Expert Panel of the Infectious Diseases Society of America. The evidence-based guidelines encompass diagnostic issues, treatment and chemoprophylaxis with antiviral medications, and issues related to institutional outbreak management for seasonal (interpandemic) influenza. They are intended for use by physicians in all medical specialties with direct patient care, because influenza virus infection is common in communities during influenza season and may be encountered by practitioners caring for a wide variety of patients.