Utility of the rapid antigen detection BinaxNOW Influenza A&B test for detection of novel influenza A (H1N1) virus

Methods of Respiratory Virus Detection: Advances towards Point-of-Care for Early Intervention

Respiratory viral infections threaten human life and inflict an enormous healthcare burden worldwide. Frequent monitoring of viral antibodies and viral load can effectively help to control the spread of the virus and make timely interventions. However, current methods for detecting viral load require dedicated personnel and are time-consuming. Additionally, COVID-19 detection is generally relied on an automated PCR analyzer, which is highly instrument-dependent and expensive. As such, emerging technologies in the development of respiratory viral load assays for point-of-care (POC) testing are urgently needed for viral screening. Recent advances in loop-mediated isothermal amplification (LAMP), biosensors, nanotechnology-based paper strips and microfluidics offer new strategies to develop a rapid, low-cost, and user-friendly respiratory viral monitoring platform. In this review, we summarized the traditional methods in respiratory virus detection and present the state-of-art technologies in the monitoring of respiratory virus at POC.

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.

A scanometric antibody probe for facile and sensitive immunoassays

We have developed a novel scanometric antibody probe for rapid, sensitive, and naked-eye-visible immunoassays. Using this probe, we clearly demonstrated the successful scanometric detection and identification of influenza A viruses on a microarray. In addition, the sensitivity of the scanometric immunoassay was comparable to that of the fluorescence-based method.

Clinical and virologic factors associated with reduced sensitivity of rapid influenza diagnostic tests in hospitalized elderly patients and young children

Rapid influenza diagnostic tests (RIDTs) are commonly used by clinicians to guide patient management. Data on sensitivities among hospitalized patients are limited. Here, we evaluated the clinical and virologic factors affecting the sensitivities of 2 commercially available RIDTs (BinaxNOW Influenza A&B and QuickVue Influenza A+B) on nasopharyngeal aspirate (NPA) specimens collected from elderly patients and young children hospitalized for influenza. Influenza cases and age-matched negative controls were prospectively enrolled during the 2011-2012 influenza season in Hong Kong. NPA specimens were collected at presentation before antiviral treatment. Real-time reverse transcription-PCR (RT-PCR) results were used as references for the sensitivity analyses. One hundred patients (57 influenza cases and 43 controls) were studied. Both RIDTs had 100% specificities. The sensitivities of the BinaxNOW Influenza A&B and QuickVue Influenza A+B tests were 70% and 82%, respectively. For both tests, the sensitivities were lower in cases with presentation times beyond 2 days of illness onset than for those within this time (50 to 71% versus 85 to 91%, respectively). There were trends toward lower sensitivities for influenza B than for influenza A (66 to 81% versus 76 to 84%, respectively), among young children than among the elderly patients (63 to 78% versus 80 to 88%, respectively), and among cases with pneumonia than those without pneumonia (75% versus 82 to 94%, respectively). The sensitivities of the RIDTs decreased with reduced NPA viral RNA levels (5.6 to 15.0% reduction per 1-log decrease), which declined progressively after illness onset (Spearman's rho, -0.47 [P < 0.05] and -0.66 [P < 0.001] for influenza A and B, respectively). Collectively, late presentation, a low NPA viral load, and probably lower respiratory manifestation are factors associated with reduced sensitivities of RIDTs for diagnosing influenza in hospitalized patients. A negative RIDT result should be interpreted with caution.

Probability of detecting influenza A virus subtypes H1N1 and H3N2 in individual pig nasal swabs and pen-based oral fluid specimens over time

The probability of detecting influenza A virus (IAV) by virus isolation (VI), point-of-care (POC) antigen detection, and real-time reverse-transcription polymerase chain reaction (rRT-PCR) was estimated for pen-based oral fluid (OF) and individual pig nasal swab (NS) specimens. Piglets (n=82) were isolated for 30 days and confirmed negative for porcine reproductive and respiratory syndrome virus, Mycoplasma hyopneumoniae, and IAV infections. A subset (n=28) was vaccinated on day post inoculation (DPI) -42 and -21 with a commercial multivalent vaccine. On DPI 0, pigs were intratracheally inoculated with contemporary isolates of H1N1 (n=35) or H3N2 (n=35) or served as negative controls (n=12). OF (n=370) was collected DPI 0-16 and NS (n=924) DPI 0-6, 8, 10, 12, 14, 16. The association between IAV detection and variables of interest (specimen, virus subtype, assay, vaccination status, and DPI) was analyzed by mixed-effect repeated measures logistic regression and the results used to calculate the probability (pˆ) of detecting IAV in OF and NS over DPI by assay. Vaccination (p-value<0.0001), DPI (p-value<0.0001), and specimen-assay interaction (p-value<0.0001) were significant to IAV detection, but virus subtype was not (p-value=0.89). Vaccination and/or increasing DPI reduced pˆ for all assays. VI was more successful using NS than OF, but both VI and POC were generally unsuccessful after DPI 6. Overall, rRT-PCR on OF specimens provided the highest pˆ for the most DPIs, yet significantly different results were observed between the two laboratories independently performing rRT-PCR testing.

Comparison of Xpert Flu rapid nucleic acid testing with rapid antigen testing for the diagnosis of influenza A and B

Influenza infections are associated with thousands of hospital admissions and deaths each year. Rapid detection of influenza is important for prompt initiation of antiviral therapy and appropriate patient triage. In this study the Cepheid Xpert Flu assay was compared with two rapid antigen tests, BinaxNOW Influenza A & B and BD Directigen EZ Flu A+B, as well as direct fluorescent antibody testing for the rapid detection of influenza A and B. Using real-time, hydrolysis probe-based, reverse transcriptase PCR as the reference method, influenza A sensitivity was 97.3% for Xpert Flu, 95.9% for direct fluorescent antibody testing, 62.2% for BinaxNOW, and 71.6% for BD Directigen. Influenza B sensitivity was 100% for Xpert Flu and direct fluorescent antibody testing, 54.5% for BinaxNOW, and 48.5% for BD Directigen. Specificity for influenza A was 100% for Xpert Flu, BinaxNOW, and BD Directigen, and 99.2% for direct fluorescent antibody testing. All methods demonstrated 100% specificity for influenza B. These findings support the use of the Xpert Flu assay in settings requiring urgent diagnosis of influenza A and B.

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.

Detection of 2009 pandemic influenza A(H1N1) virus Infection in different age groups by using rapid influenza diagnostic tests

BACKGROUND

The performance of rapid influenza diagnostic tests (RIDTs) in detecting influenza A(H1N1) 2009 has varied widely. Evaluations of RIDTs among infected individuals across all age groups have not been described in depth.

OBJECTIVES

Determine RIDT clinical sensitivity in comparison with influenza detection using real-time RT-PCR among patients infected with influenza A(H1N1) 2009 across all age groups.

STUDY DESIGN

This study analyzed respiratory specimens received by the New Hampshire Public Health Laboratories (NHPHL) from September 1, 2009, through December 31, 2009. RIDT performance was evaluated among different age groups of patients determined to be infected with influenza A (H1N1) 2009, and the association between age and RIDT sensitivity was determined.

RESULTS

Of 1373 specimens examined, 269 tested positive for influenza A(H1N1) 2009 by real-time RT-PCR (rRT-PCR) and had RIDT results available. Overall clinical sensitivity and specificity of RIDTs were 53·9 and 98·5%, respectively. By age group, clinical sensitivity was 85·7% in patients <2 years old, 60·3% in patients between 2- and 39 years old, and 33·3% in patients aged 40 and older. Logistic regression analysis indicated that increasing age was negatively associated with RIDT performance.

CONCLUSION

Rapid influenza diagnostic test sensitivity decreased significantly with increasing age. Findings from this study may impact a clinician's interpretation of RIDT test results and ultimately have implications in clinical decision-making.

Performance of rapid influenza H1N1 diagnostic tests: a meta-analysis

Please cite this paper as: Chu et al. (2011) Performance of rapid influenza H1N1 diagnostic tests: a meta‐analysis. Influenza and Other Respiratory Viruses DOI: 10.1111/j.1750‐2659.2011.00284.x.

Background  Following the outbreaks of 2009 pandemic H1N1 infection, rapid influenza diagnostic tests have been used to detect H1N1 infection. However, no meta‐analysis has been undertaken to assess the diagnostic accuracy when this manuscript was drafted.

Methods  The literature was systematically searched to identify studies that reported the performance of rapid tests. Random effects meta‐analyses were conducted to summarize the overall performance.

Results  Seventeen studies were selected with 1879 cases and 3477 non‐cases. The overall sensitivity and specificity estimates of the rapid tests were 0·51 (95%CI: 0·41, 0·60) and 0·98 (95%CI: 0·94, 0·99). Studies reported heterogeneous sensitivity estimates, ranging from 0·11 to 0·88. If the prevalence was 30%, the overall positive and negative predictive values were 0·94 (95%CI: 0·85, 0·98) and 0·82 (95%CI: 0·79, 0·85). The overall specificities from different manufacturers were comparable, while there were some differences for the overall sensitivity estimates. BinaxNOW had a lower overall sensitivity of 0·39 (95%CI: 0·24, 0·57) compared with all the others (P‐value <0·001), whereas QuickVue had a higher overall sensitivity of 0·57 (95%CI: 0·50, 0·63) compared with all the others (P‐value = 0·005).

Conclusions  Rapid tests have high specificity but low sensitivity and thus limited usefulness.