Comparison of the Binax NOW Flu A enzyme immunochromatographic assay and R-Mix shell vial culture for the 2003-2004 influenza season

Improving Accuracy of Influenza-Associated Hospitalization Rate Estimates

Adjusting for diagnostic test sensitivity enables more accurate and timely comparisons over time.

Diagnostic test sensitivity affects rate estimates for laboratory-confirmed influenza–associated hospitalizations. We used data from FluSurv-NET, a national population-based surveillance system for laboratory-confirmed influenza hospitalizations, to capture diagnostic test type by patient age and influenza season. We calculated observed rates by age group and adjusted rates by test sensitivity. Test sensitivity was lowest in adults >65 years of age. For all ages, reverse transcription PCR was the most sensitive test, and use increased from <10% during 2003–2008 to ≈70% during 2009–2013. Observed hospitalization rates per 100,000 persons varied by season: 7.3–50.5 for children <18 years of age, 3.0–30.3 for adults 18–64 years, and 13.6–181.8 for adults >65 years. After 2009, hospitalization rates adjusted by test sensitivity were ≈15% higher for children <18 years, ≈20% higher for adults 18–64 years, and ≈55% for adults >65 years of age. Test sensitivity adjustments improve the accuracy of hospitalization rate estimates.

Microbiological diagnosis of community-acquired respiratory tract infections by nucleic acid detection

BACKGROUND

Microbiological diagnostic procedures have changed significantly over the last decade. Initially the implementation of the polymerase chain reaction (PCR) resulted in improved detection tests for microbes that were difficult or even impossible to detect by conventional methods such as culture and serology, especially in community-acquired respiratory tract infections (CA-RTI). A further improvement was the development of real-time PCR, which allows end point detection and quantification, and many diagnostic laboratories have now implemented this powerful method.

OBJECTIVE

At present, new performant and convenient molecular tests have emerged targeting in parallel many viruses and bacteria responsible for lower and/or upper respiratory tract infections. The range of test formats and microbial agents detected is evolving very quickly and the added value of these new tests needs to be studied in terms of better use of antibiotics, better patient management, duration of hospitalization and overall costs.

CONCLUSIONS

Molecular tools for a better microbial documentation of CA-RTI are now available. Controlled studies are now required to address the relevance issue of these new methods, such as, for example, the role of some newly detected respiratory viruses or of the microbial DNA load in a particular patient at a particular time. The future challenge for molecular diagnosis will be to become easy to handle, highly efficient and cost-effective, delivering rapid results with a direct impact on clinical management.

Updated values for molecular diagnosis for highly pathogenic avian influenza virus

Highly pathogenic avian influenza (HPAI) viruses of the H5N1 strain pose a pandemic threat. H5N1 strain virus is extremely lethal and contagious for poultry. Even though mortality is 59% in infected humans, these viruses do not spread efficiently between humans. In 1997, an outbreak of H5N1 strain with human cases occurred in Hong Kong. This event highlighted the need for rapid identification and subtyping of influenza A viruses (IAV), not only to facilitate surveillance of the pandemic potential of avian IAV, but also to improve the control and treatment of infected patients. Molecular diagnosis has played a key role in the detection and typing of IAV in recent years, spurred by rapid advances in technologies for detection and characterization of viral RNAs and proteins. Such technologies, which include immunochromatography, quantitative real-time PCR, super high-speed real-time PCR, and isothermal DNA amplification, are expected to contribute to faster and easier diagnosis and typing of IAV.

Diagnostic performance of the BinaxNow Influenza A&B rapid antigen test in ED patients

OBJECTIVE

The objective of this study is to evaluate the diagnostic performance of the BinaxNow Influenza A&B rapid antigen test (RAT) in emergency department (ED) patients.

METHODS

We prospectively enrolled a systematic sample of ED patients older than 6 months with acute respiratory symptoms or nonlocalizing fever during 3 consecutive influenza seasons (2008-2011). Nasal and throat swabs collected by research personnel were tested for influenza by real-time reverse transcription-polymerase chain reaction (RT-PCR). Clinicians independently ordered RATs during clinical care; these specimens were collected by clinical staff and tested for influenza using the BinaxNow RAT. Patients with both a research RT-PCR and clinical RAT were included in the study. Rapid antigen test diagnostic performance was evaluated using RT-PCR as a criterion standard, with preplanned, stratified analysis for subject age, duration of symptoms, influenza subtype, and polymerase chain reaction cycle threshold, which provides a semiquantitative estimate of viral load.

RESULTS

Of 561 subjects enrolled, 131 (23.4%) had a positive RT-PCR, and 37 (6.6%) had a positive RAT. Overall, RAT performance included sensitivity of 24.4% (95% confidence interval [CI], 17.5%-32.9%), specificity of 98.8% (95% CI, 97.1%-99.6%), positive predictive value of 86.5% (95% CI, 70.4%-94.9%), negative predictive value of 81.1% (95% CI, 77.4%-84.3%). Rapid antigen test sensitivities were low for all categories of subject age, symptom duration, influenza subtype, and cycle threshold.

CONCLUSION

The BinaxNow RAT demonstrated high specificity and poor sensitivity in ED patients selected by treating clinicians for influenza testing. A negative RAT is a poor predictor for the absence of influenza in the ED and should not be used as a criterion to withhold antiviral medications.

Rapid antigen tests for diagnosis of pandemic (Swine) influenza A/H1N1

We found that the sensitivities of 3 rapid influenza antigen tests for pandemic influenza A/H1N1 virus were low to moderate: BD Directigen EZ Flu A+B test (Becton Dickinson), 46.7%; BinaxNOW Influenza A&B (Inverness Medical), 38.3%; and QuickVue Influenza A+B Test (Quidel), 53.3%. A patient with influenza-like illness who has a negative rapid antigen test result should undergo further testing using reverse-transcription polymerase chain reaction.

Near-patient assays for diagnosis of influenza virus infection in adult patients

Rapid and reliable diagnosis of influenza is essential for identification of contagious patients and effective patient management. Near‐patient assays allow establishment of the diagnosis within minutes in young children, and this study aimed to evaluate near‐patient assays in relation to the patient’s age. A total of 194 patients with laboratory‐confirmed influenza A/H3N2 virus infection, diagnosed within a prospective cohort study, were included. Cryopreserved nasopharyngeal swabs collected from these patients were tested by four near‐patient assays (Binax Now Influenza A&B, Quick S‐Influ A/B, Influ‐A&B Respi‐Strip, and Actim Influenza A&B). The main outcome measure was sensitivity of the near‐patient assays in relation to the age of patients. The Binax Now, Quick S‐Influ, Influ‐A&B Respi‐Strip and Actim assays had overall sensitivities of 19%, 18%, 26%, and 40%, respectively. The estimated sensitivity for influenza A/H3N2 virus detection in nasopharyngeal swabs was 17–56% in children 1 year of age and decreased to 8–22% in patients 80 years of age (logistic regression). The sensitivity of the Influ‐A&B Respi‐Strip and Actim assays decreased significantly with increasing age (p 0.014 and p 0.033, respectively (logistic regression)), a trend for decrease was observed for the Binax Now assay (p 0.074 (logistic regression)), and the low sensitivity of the Quick S‐Influ assay was similar in children and adults. Less than one‐fourth of diagnosed influenza A/H3N2 virus infections can be identified in elderly patients using a near‐patient assay. Consequently, near‐patient assays are of limited value for confirming the diagnosis when influenza is clinically suspected in adults. Antiviral therapy and additional diagnostic procedures cannot be withheld on the basis of a negative near‐patient assay result, particularly in adult patients.

Performance of Binax NOW Flu A and B and direct fluorescent assay in comparison with a composite of viral culture or reverse transcription polymerase chain reaction for detection of influenza infection during the 2006 to 2007 season

The Binax NOW Flu A and Flu B (Binax NOW), direct fluorescent assay (DFA), and viral culture were evaluated and compared with a composite of viral culture or reverse transcription polymerase chain reaction (RT-PCR). Participants with medically attended acute respiratory illness were identified through active surveillance during the 2006 to 2007 season, and consenting individuals (n=932) were tested for influenza by culture and RT-PCR. Physicians ordered a rapid antigen test (Binax NOW [n=73] or DFA [n=70]) according to their clinical judgment. The Binax NOW detected 11 of 18 influenza infections (sensitivity, 61%; 95% confidence interval [CI], 36-83%), whereas DFA detected 17 of 21 influenza infections (sensitivity 81%, 95% CI, 58-95%). Compared with culture/RT-PCR, specificity of both Binax NOW and DFA was 100%. During the 2006 to 2007 influenza season, DFA and Binax NOW demonstrated high specificity but failed to identify a substantial proportion of influenza infections.

[Respiratory viruses: old and new. Review of diagnostic methods]

Acute respiratory infections (ARI) of viral origin are one of the main causes of morbidity and mortality worldwide. In addition to traditional viruses, such as the influenza virus, respiratory syncytial virus, rhinovirus, parainfluenza viruses 1 to 4, and adenovirus, other viruses such as metapneumovirus, new coronaviruses (human coronavirus NL63 and HKU1 and severe acute respiratory syndrome [SARS]-coronavirus), and recently bocaviruses, have been identified as causal agents of ARI. Although most of these viral infections follow a benign and selflimiting course in healthy adults, the consequences for the health care systems increase when they involve children, the elderly, immunosuppressed individuals, or those with chronic underlying diseases. These viral infections are an important cause of hospitalization and death, mainly during the cold months of the year, and, from a social-health perspective, ARI are a drain on economic resources and a frequent cause of work absenteeism. Occasionally, some of these viruses may cause emergent world health problems, as has occurred with the influenza virus pandemic strain and SARScoronavirus. While classical diagnostic methods based on culture and antigen detection remain useful for traditional respiratory viruses, recently described viruses are diagnosed mainly by molecular amplification techniques.

Role of the laboratory in diagnosis of influenza during seasonal epidemics and potential pandemics

Laboratory diagnosis of influenza is critical to its treatment and surveillance. With the emergence of novel and highly pathogenic avian influenza viruses, the role of the laboratory has been further extended to include isolation and subtyping of the virus to monitor its appearance and facilitate appropriate vaccine development. Recent progress in enhancing testing for influenza promises to both improve the management of patients with influenza and decrease associated health care costs. The present review covers the technological characteristics and utilization features of currently available diagnostic tests, the factors that influence the selection of such tests, and the developments that are essential for pandemic preparedness.

Comparison of the MChip to viral culture, reverse transcription-PCR, and the QuickVue influenza A+B test for rapid diagnosis of influenza

The performance of a diagnostic microarray (the MChip assay) for influenza was compared in a blind study to that of viral culture, reverse transcription (RT)-PCR, and the QuickVue Influenza A+B test. The patient sample data set was composed of 102 respiratory secretion specimens collected between 29 December 2005 and 2 February 2006 at Scott & White Hospital and Clinic in Temple, Texas. Samples were collected from a wide range of age groups by using direct collection, nasal/nasopharyngeal swabs, or nasopharyngeal aspiration. Viral culture and the QuickVue assay were performed at the Texas site at the time of collection. Aliquots for each sample, identified only by study numbers, were provided to the University of Colorado and Vanderbilt University teams for blinded analysis. When referenced to viral culture, the MChip exhibited a clinical sensitivity of 98% and a clinical specificity of 98%. When referenced to RT-PCR, the MChip assay exhibited a clinical sensitivity of 92% and a clinical specificity of 98%. While the MChip assay currently requires 7 to 8 h to complete the analysis, a significant advantage of the test for influenza virus-positive samples is simultaneous detection and full subtype identification for the two subtypes currently circulating in humans (A/H3N2 and A/H1N1) and avian (A/H5N1) viruses.

Role of cell culture for virus detection in the age of technology

Viral disease diagnosis has traditionally relied on the isolation of viral pathogens in cell cultures. Although this approach is often slow and requires considerable technical expertise, it has been regarded for decades as the "gold standard" for the laboratory diagnosis of viral disease. With the development of nonculture methods for the rapid detection of viral antigens and/or nucleic acids, the usefulness of viral culture has been questioned. This review describes advances in cell culture-based viral diagnostic products and techniques, including the use of newer cell culture formats, cryopreserved cell cultures, centrifugation-enhanced inoculation, precytopathogenic effect detection, cocultivated cell cultures, and transgenic cell lines. All of these contribute to more efficient and less technically demanding viral detection in cell culture. Although most laboratories combine various culture and nonculture approaches to optimize viral disease diagnosis, virus isolation in cell culture remains a useful approach, especially when a viable isolate is needed, if viable and nonviable virus must be differentiated, when infection is not characteristic of any single virus (i.e., when testing for only one virus is not sufficient), and when available culture-based methods can provide a result in a more timely fashion than molecular methods.

Relevance of influenza a virus detection by PCR, shell vial assay, and tube cell culture to rapid reporting procedures

Influenza A virus was detected at higher rates and for more extended time periods with real-time PCR than with cell cultures. We show here that, using the theranostic approach, rapid viral detection and reporting can provide for early implementation and assessment of available antiviral therapy.

Evaluation of the Quidel QuickVue test for detection of influenza A and B viruses in the pediatric emergency medicine setting by use of three specimen collection methods

The Quidel QuickVue influenza test was compared to viral culture and reverse transcriptase PCR by the use of three different respiratory specimen types. Of 122 pediatric subjects enrolled, 59 had influenza virus infections: 44 were infected with influenza A virus and 15 were infected with influenza B virus. The sensitivity of the QuickVue test was 85% with nasopharyngeal swabs, 78% with nasal swabs, and 69% with nasopharyngeal washes. Specificities were equivalent (97% to 98%) for all three collection methods.