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

Article (PDF Available)inDiagnostic Microbiology and Infectious Disease 62(2):162-6 · December 2007with150 Reads
DOI: 10.1016/j.diagmicrobio.2007.10.012 · Source: PubMed
Abstract
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.

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Available from: Mahbubur Rahman, Sep 03, 2014
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
Mahbubur Rahman
a,
, Mary F. Vandermause
b
, Burney A. Kieke
b
, Edward A. Belongia
b
a
Center for Interdisciplinary Research in Women's Health, The University of Texas Medical Branch, Galveston, TX 77555-0587, USA
b
Marshfield Clinic Research Foundation and Marshfield Clinic, Marshfield, WI 54449, USA
Received 15 June 2007; accepted 9 October 2007
Abstract
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], 3683%), whereas DFA
detected 17 of 21 influenza infections (sensitivity 81%, 95% CI, 5895%). 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.
© 2008 Elsevier Inc. All rights reserved.
Keywords: Influenza virus; Rapid test; Binax NOW; Direct fluorescent assay; Sensitivity; Specificity
1. Introduction
Influenza infections are an important cause of mortality
and morbidity worldwide. Rap id diagnosis of influenza
infections is imp ortant because antiviral drugs are only
effective if started within 48 h after symptom onset
(Younkin et al., 1983; Reuman et al., 1989; Hayd en et al.,
1999). Early diagnosis is also important because it reduces
the length of hospital stays and may reduce unnecessary
antibiotic use (Woo et al., 1997; Barenfanger et al., 2000).
However, rapid diagnosis is a challenging task. Diagnosis of
influenza infection based on on ly clinical features is
difficult due to its nonspecific presentation and cocircula-
tion of other respiratory viruses during influenza epidemics.
Several office-based commercial rapid tests are available for
detecting influenza viruses to assist in patient management
(Storch, 2003). These tests do not require special expertise
and can be completed within minutes, but low test
sensitivity has been a concern despite high specificity.
Binax NOW Influenza A and B test kit (Binax, Portland,
ME) is a recent addition to the list of commercial rapid tests,
but limited information is available regarding the perfor-
mance of the test in different populations. Direct fluorescent
assay (DFA) is another option at some laboratories for
timely access to influenza test results, but it requires
significant technical expertise and equipment (Landry and
Ferguson, 2003). Reverse transcription polymerase chain
reaction (RT-PCR) provi des sensitive and speci fic detection
of influenza viruses, but this technology currently requires
special equipment and expertise, and is not widely available
in most clinical settings.
A
vailable online at www.sciencedirect.com
Diagnostic Microbiology and Infectious Disease 62 (2008) 162 166
www.elsevier.com/locate/diagmicrobio
Funding for this research was provided by a cooperative agreement
with the Centers for Disease Control and Prevention, Atlanta, GA (1 U01
CI000192-01). The findings and conclusions in this report are those of the
authors and do not necessarily represent the views of the funding agency.
Corresponding author. Tel.: +1-409-772-2978; fax: +1-409-747-5129.
E-mail address: marahman@utmb.edu (M. Rahman).
0732-8893/$ see front matter © 2008 Elsevier Inc. All rights reserved.
doi:10.1016/j.diagmicrobio.2007.10.012
During the 2006 to 2007 influenza season, we evaluated
the performance of the Binax NOW and DFA in comparison
with a composite gold standard based on viral culture and
RT-PCR. The latter tests were performed on patients with
acute respiratory illness who were recruited for a study of
influenza vaccine effectiveness.
2. Materials and methods
2.1. Participants
Participants for this investigation were derived from a
population-based study of influenza vaccine effectiveness
conducted within the Marshfield Epidemiologic Study Area,
a 14-ZIP code region surrounding Marshfield, WI (DeSte-
fano et al., 1996). Patients receiving inpatient or outpatient
care for acute respiratory illness b10 days in duration were
recruited and tested for influenza infection by viral culture
and RT-PCR. During the influenza season, 932 patients were
enrolled and tested from a source population of 20 693
residents who were eligible to receive the 2006 to 2007
influenza vaccine based on recommendations from the
Advisory Committee on Immunization Practices (ACIP)
(Smith et al., 2006). These included all children 6 to
59 months old, all adults 50 years old, and individuals
aged 5 years through 49 years with specific high-risk
medical conditions.
Enrollment began on January 22, 2007, and continued
for 10 weeks. For this study, we identified enrolled
patients who also had a rapid test ordere d by the physician
in their routine clinical practice. Physicians ordered a rapid
test based on clinical indication, independent of the
research tests for influenza. The latter test results were
usually not available until more than 1 week later, and the
research test results were not included in the patient's
medical record. As a result, primary care physicians were
encouraged to maintain their usual testing procedures for
influenza despite concurrent testing for a vaccine effec-
tiveness study.
Physicians did not specify the type of rapid test when
ordered, and the use of DFA or Binax NOW was determined
by the timing and location of the sample. Binax NOW was
performed in the regional clinic centers and in the main clinic
during evening and weekend hours. DFA was performed in
the m ain clinic during normal working hours when
experienced technicians were available.
2.2. Collection of specimens
All samples that had a Binax NOW or DFA test performed
were ordered and collected by the physician or physician's
medical assistant according to clinic protoco l. In all cases,
nasopharyngeal swabs were obtained, placed in M4-RT viral
transport media (Remel, Lenexa, KS), and transported to the
clinical laboratory on ice within 2 h. The same sample swab
was used for viral culture, RT-PCR, and rapid antigen tests
(Binax NOW or DFA).
2.3. Binax NOW
The Binax NOW Influenza A and B test kit is an
immunochromatographic membrane assay that uses highly
sensitive monoclonal antibodies to detect influenza A and B
nucleoprotein antigens in 15 min. Nasopharyngeal swabs,
collected and transported in the viral transport media, were
vortexed. One hundred microliters were applied directly to
the test cartridge. Results were read in 15 min, as per
manufacturers package insert. For a negative sample, the
blue control line turns to a pink-to-purple color. No other
line appears. For an influenza A-positive sample, the blue
control line turns to a pink-to-purple color, and a 2nd
pink-to-purple line appears in the designated Flu A area.
For an influenza B-positive sample, the blue control line
turns to a pink-to-purple color, and a 2nd pink-to-purple
line appears in the designated Flu B area. A test is
considered invalid if the control line remains blue or is not
present at all.
2.4. Direct fluorescent assay
DFAs allow visual localization of viral antigen within
infected cells. Nasopharyngeal swabs, collected and trans-
ported in the viral transport media, were vortexed. The
beads contained in the viral transport aided in breaking up
mucus in the specimen and releasing cells from the
mucous and swab fibers. The swab was removed and the
specimen was centrifuged at 600×g for 5 min to obtain a
cell pellet concentrated in the bottom of the conical
transport tube. The supernatant was transferred to a
separate tube and stored at 4 to 8 °C for any subsequen t
testing. The pellet was twice washed in phosphate-buffered
saline (PBS) and centrifuged again. The final centrifuged
pellet was resuspended in 400 μL of PBS and spotted onto
a 3-well microscope slide. Slides were dried, acetone fixed,
and stained using monoclonal fluorescein-labeled antibo-
dies for influenza A and B (D
3
Influenza A/Influenza B
DFA Reagent Kit; Diagnostic Hybrids, Athens, OH). The
slides were read by an experienced technician using a
fluorescence microscope. The sample was considered
adequate if 200 cells were observed on the slide with at
least 2 columnar epithelial cells/250× field. Specimens
were considered positive for influenza A or B if at least
1 cell showed characteristic influenza nuclear and/or
cytoplasmic fluor escence.
2.5. Viral culture
Virus cultures for the isolation of influenza A and B were
performed by inoculating monolayered MadinDarby
canine kidney epithelial cells in shell vial cell cultures
(Diagnostic Hybrids) with 200 μL of the sample supernatant.
Inoculated shell vials were centrifuged for 1 h at 700×g
(2000 rpm) and incubated at 35 to 37 °C. Cultures were
examined microscopically for cytopathic effect for up to 72 h
postinoculation. Cell culture shell vials were maintained
using standard shell vial techniques. Laboratory protocols
163M. Rahman et al. / Diagnostic Microbiology and Infectious Disease 62 (2008) 162166
for quality control and monitoring cell suit ability were
followed. After detection of cytopathic effect, or if no
cytopathic effect was detected by 72 h, the cell sheet was
scraped and/or dislodged from the surface of the coverslip at
the bottom of the shell vial. Slides were prepar ed using the
cell scraping, dried, acetone fixed, and stain ed with
fluorescein-labeled virus-specific monoclonal antibody
reagents (D
3
Influenza A/Influenza B DFA Reagent Kit,
Diagnostic Hybrids) intended for the qualitative detection
and identification of influenza A and influenza B. Slides
were read using a fluorescent microscope.
2.6. Reverse transcription polymerase chain reaction
RT-PCR was performed on nucleic acid extracts from
specimens using the LightCycler® Real-Time PCR System
(Roche Diagnostics, Basel, Switzerland). Total nucleic acid
isolation and purification were performed using automated
magnetic bead technology. RT-PCR primers, probes, and
protocols for influenza A and B were provided by Centers for
Disease Control and Prevention. The primers and probes
have been previously proven to be highly conserved and
make an effective target for detection. The primer/probe sets
were designed for universal detection of type A and type B
influenza viruses. The human RNase P gene (RNP) primer
and probe set serves as an internal positive control for human
RNA. Standard laboratory safeguards were incorporated into
the protocol to decrease the risk of carryover amplicon
contamination including the use of uracil glycosylase, 3
separate unidirectional workflow areas, and laboratory
surface decontamination products to eliminate residual
DNA/RNA.
For this study, positive viral cultures for influenza A
or B or positive results in RT-PCR were considered as
true positives.
2.7. Statistical analysis
Sensitivity, specificity, positive predictive value, and
negative predictive value of the Binax NOW and DFA tests
were calculated in comparison with a composite gold
standard of viral culture or RT-PCR. Corresponding 95%
confidence intervals (CIs) were computed using exact
methods (Collett, 1991). Univariate comparisons were
performed using the χ
2
test, Fisher's exact test, or Wilcoxon
rank sum test as appropriate. All analyses were performed
using SAS 9.1 (SAS Institute, Cary, NC) or STATA 9 (Stata,
College Station, TX).
3. Results
3.1. Demographics and clinical characteristics
Physicians ordered an influenza rapid test in 143 (15%) of
study participants with acute respiratory illness b10 days in
duration. The clinical laboratory performed Binax NOW in
73 (51%) and DFA in 70 (49%) of these patients. Patients
who received a rapid influenza test were older and were more
likely to have a high-risk medical condition relative to
patients with acute respiratory illness who did not receive a
rapid test. Patients who had a rapid test also had a higher
prevalence of infl uenza infection and were more likely to
present for care during the first 2 days after symptom onset
(Table 1). Gender and vaccination status during the 2006 to
2007 season were similarly distributed for those who did and
Table 1
Baseline characteristics of the study participants with and without Binax
NOW/DFA ordered
Characteristics Binax
NOW/DFA
ordered
(n = 143)
No. (%)
Binax
NOW/DFA
not ordered
(n = 789)
No. (%)
P
a
Age group b0.001
659 months 51 (36) 478 (61)
517 years 10 (7) 51(6)
1849 years 11 (8) 48 (6)
5064 years 41 (29) 123 (16)
65 years 30 (21) 89 (11)
Male gender 73 (51) 362 (46) 0.254
With high-risk medical
condition
b
65 (45) 239 (30) b0.001
Influenza vaccination
during 2006 to 2007
74 (52) 455 (58) 0.189
Duration of symptoms
at 1st clinical encounter
b0.001
2 days 75 (52) 244 (31)
N2 days 68 (48) 545 (69)
Culture/RT-PCR positive
for influenza
39 (27) 63 (8) b0.001
a
P value for the χ
2
test.
b
High-risk conditions were based on ACIP criteria for persons at
increased risk of influenza complications due to chronic disease (specific
diagnosis codes available on request).
Table 2
Performance of Binax NOW and DFA compared with a composite gold
standard (viral culture or RT-PCR) for detection of influenza virus
Age group No of specimens Se Sp PPV NPV
TP FP FN TN Total
Binax NOW
Overall 11
a
07
b
55 73 61 100 100 89
6 months to 17 years 5 0 1 21 27 83 100 100 95
18 years 6 0 6 34 46 50 100 100 85
DFA
Overall 17
c
04
a
49 70 81 100 100 92
6 months to 17 years 9 0 4 21 34 69 100 100 84
18 years 8 0 0 28 36 100 100 100 100
TP = true positive; FP = false positive; FN = false negative; TN = true
negative; Se = sensitivity; Sp = specificity; PPV = positive predictive value;
NPV = negative predictive value.
a
All influenza A infections.
b
Five influenza A and 2 influenza B infections.
c
One influenza B infection.
164 M. Rahman et al. / Diagnostic Microbiology and Infectious Disease 62 (2008) 162166
who did not have a rapid test. No significant demographic
differences were found between those who had the Binax
NOW and DFA.
3.2. Accuracy of Binax NOW
Of the 73 specimens, Binax NOW identified 11 of 18
culture/RT-PCRpositive influenza infections. The sensitiv-
ity and specificity of Binax NOW was 61% (95% CI, 36
83%) and 100% (95% CI, 94100%), respectively, with a
positive predictive value of 100% (95% CI, 72100%) and a
negative predictive value of 89% (95% CI, 7895%).
Although the sensitivity of Binax NOW was higher in
children and adolescents compared with the adult popula-
tion, the difference was not statistically significant (P =
0.316) (Table 2). Performance of Binax NOW did not differ
when either viral culture or RT-PCR was used as the gold
standard (Table 3).
3.3. Accuracy of DFA
DFAidentified17of21culture/RT-PCRpositive
influenza infections, yielding a sensitivity of 81% (95%
CI, 5895%). DFA was negative in all 49 patients with a
negative culture/RT-PCR (specificity, 100%; 95% CI, 93
100%). The positive and negative predictive values were
100% (95% CI, 80100%) and 92% (95% CI, 8298%),
respectively. DFA had a higher sensitivity in the adult
population compared with children and adolescen ts, but
the difference was not statistically significant (P = 0.131)
(Table 2). Accuracy of the test did not change substantially
when either viral culture or RT-PCR test was used as the
gold standard (Table 3).
The sensitivity of DFA was not significantly different than
that of Binax NOW (P = 0.17).
3.4. Detection of influenza infection by viral culture
and RT-PCR
Based on a composite gold standard (culture confirmed
or PCR positive), viral culture detected 93 (sensitivity,
91%; 95% CI, 8496%) and RT-PCR detected 98 of 102
influenza infections (sensitivity, 96%; 95% CI, 9099%).
In total, 89 specimens were positive for influenza virus
both with RT-PCR and viral culture, 9 with RT-PCR only,
and 4 with viral culture only. Specificity of both viral
culture and RT-PCR was 100%. Although based on a
limited number of observations, both viral culture and RT-
PCR demonstrated 100% sensitivity for detecting influenza
B infections.
4. Discussion
During the 2006 to 2007 season, Binax NOW detected
approximately two thirds of influenza infections. The
sensitivity estimate of the assay generated in this study
(61%) was within the range reported in the literature (56
76%) (Cruz et al., 2006; Smit et al., 2007; Landry et al.,
2004; Weinberg and Walker, 2005; Fader 2005; Hurt et al.,
2007). Although we did not observe a statistically
significant difference in test sensitivity in children versus
adults, the relatively high sensitivity in children is
consistent with previously published results ( Landry
et al., 2004; Weinberg and Walker, 2005; Fader, 2005;
Hurt et al., 2007). A decrease in sensitivity in adult
patients has also been observed with other enzyme
immunoassay rapid tests for detecting influenza infections
(Yamazaki et al., 2000; Chan et al., 2002; Reina et al.,
2002; Caz acu et al., 2003; Hamilton et al., 2002; Ruest
et al., 2003; Cazacu et al., 2004; Landry et al., 2004;
Alexander et al., 2005). Higher viral excretion by children
has been suggested as a possible mechanism for higher
sensitivity in children (Landry et al., 2000).
The sensitivities and the specificities of DFA reported
range from 59% to 100% and 90% to 100%, respectively
(Daisy et al., 1979; Reina et al., 1996; Landry et al., 2000;
Chan et al., 2002; Quach et al., 2002; Habib-Bein et al.,
2003; Landry and Ferguson, 2003; Shetty et al., 2003;
Rahman et al., 2007), which are also consistent with our
findings. We observed that DFA had greater sensitivity
in adults relative to children, although the difference
was not stat istically significant. However, power was
limited to assess age-related differences because only 8
influenza infections were detected in adults who were
tested by DFA.
The strength of our study includes its population-based
study design and the use of 2 different gold standard tests.
The limitations of our study were a small sample size and
the lack of standardized criteria for use of the rapid test
because clinicians ordered rapid influenza tests based on
their clinical judgment. Few i nfluenza B infections
occurred in the study population, and it was not possible
to assess the performance of Binax NOW for influenza B.
Performance of DFA in our study is not generalizable due
to the fact that it is not a standardized test and solely
depends on individual expertise.
In conclusion, during the 2006 to 2007 influenza
season, DFA and Binax NOW demonstrated high specifi-
city but failed to identify a substantial proportion of
influenza infections.
Table 3
Detection of influenza virus by Binax NOW and DFA in comparison with
viral culture and RT-PCR
Viral culture Se
(%)
RT-PCR Se
(%)
Positive Negative Positive Negative
Binax 65 61
Positive 11 0 11 0
Negative 6 56 7 55
DFA
Positive 17 0 85 17 0 81
Negative 3 50 4 49
Specificity was always 100%.
165M. Rahman et al. / Diagnostic Microbiology and Infectious Disease 62 (2008) 162166
Acknowledgments
The authors are indebted to Craig Becker, Richard Berg,
Carol Beyer, Marilyn Bruger, Autumn Deedon, Theresa
Esser, Jayne Frahmann, Julie Friedhoff, Gregg Greenw ald,
Deborah Hilgemann, Kate Konitzer, Jordon Ott, Salah
Qutaishat, Melanie Rayhorn, Sonia Stratman, Sandra Strey,
and Kari Weik for their assistance.
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166 M. Rahman et al. / Diagnostic Microbiology and Infectious Disease 62 (2008) 162166
    • "The BinaxNow influenza and RSV (ICT) assays are commonly used and many clinical studies have addressed sensitivity and specificity before, showing a lot of variation. [8][9][10][11][12][13][14][15][16][17][18][19][20] The published sensitivity varied between a modest 59%–83% for influenza A virus, 72%–90% for RSV and a poor sensitivity for influenza B virus (33%–69%). The ICT sensitivity observed in our study confirms these findings. "
    [Show abstract] [Hide abstract] ABSTRACT: Background: Clinical signs and symptoms of different airway pathogens are generally indistinguishable, making laboratory tests essential for clinical decisions regarding isolation and antiviral therapy. Immunochromatographic tests (ICT) and direct immunofluorescence assays (DFA) have lower sensitivities and specificities than molecular assays, but have the advantage of quick turnaround times and ease-of-use. Objective: To evaluate the performance of a rapid molecular assay, ARIES FluA/B & RSV, using laboratory developed RT-PCR assays (LDA), ICT (BinaxNOW) and DFA. Methods: Analytical and clinical performance were evaluated in a retrospective study arm (stored respiratory samples obtained between 2006-2015) and a prospective study arm (unselected fresh clinical samples obtained between December 2015 and March 2016 tested in parallel with LDAs). Results: Genotype inclusivity and analytical specificity was 100%. However, ARIES was 0.5 log, 1-2logs and 2.5logs less sensitive for fluA, RSV and fluB respectively, compared to LDA. In total, 447 clinical samples were included, of which 15.4% tested positive for fluA, 9.2% for fluB and 26.0% for RSV, in both LDA and ARIES. ARIES clinical sensitivity compared to LDA was 98.6% (fluA), 93.3% (fluB) and 95.1% (RSV). Clinical specificity was 100% for all targets. ARIES detected 10.6% (4 fluA, 8 fluB, 11 RSV) and 26.9% (7 fluA, 3 fluB, 22 RSV) more samples compared to DFA and ICT, all confirmed by LDA. Conclusion: Although analytically ARIES is less sensitive than LDA, the clinical performance of the assay in our tertiary care setting was comparable, and significantly better than that of the established rapid assays.
    Full-text · Article · Nov 2016
    Jolanda J.C. VoermansJolanda J.C. VoermansS. Seven-DenizS. Seven-DenizP.L.A. Fraaij+2 more authors ...Suzan D. PasSuzan D. Pas
    • "The BinaxNow influenza and RSV (ICT) assays are commonly used and many clinical studies have addressed sensitivity and specificity before, showing a lot of variation. [8][9][10][11][12][13][14][15][16][17][18][19][20] The published sensitivity varied between a modest 59%–83% for influenza A virus, 72%–90% for RSV and a poor sensitivity for influenza B virus (33%–69%). The ICT sensitivity observed in our study confirms these findings. "
    Full-text · Article · Sep 2016 · Future Microbiology
    • "None of the diagnostic tests discussed so far are easily carried out in the field, and none can provide virtually instant results. Rapid pointof-care diagnosis is critical for the control and Review El Zowalaty, Bustin, Husseiny & Ashour management of influenza infection in humans, as it enables the fast administration of appropriate antiviral therapy within the first 2 days of illness [161], reduces the length of in-patient hospital stay and minimizes the unnecessary use of antibiotics [162] . Rapid antigen capture immunoassay tests can provide results within 30 min or less and are easy to perform [163]. "
    [Show abstract] [Hide abstract] ABSTRACT: Avian influenza virus (AIV) is the causative agent of a zoonotic disease that affects populations worldwide with often devastating economic and health consequences. Most AIV subtypes cause little or no disease in waterfowl, but outbreaks in poultry can be associated with high mortality. Although transmission of AIV to humans occurs rarely and is strain dependent, the virus has the ability to mutate or reassort into a form that triggers a life-threatening infection. The constant emergence of new influenza strains makes it particularly challenging to predict the behavior, spread, virulence or potential for human-to-human transmission. Because it is difficult to anticipate which viral strain or what location will initiate the next pandemic, it is difficult to prepare for that event. However, rigorous implementation of biosecurity, vaccination and education programs can minimize the threat of AIV. Global surveillance programs help record and identify newly evolving and potentially pandemic strains harbored by the reservoir host.
    Full-text · Article · Sep 2013
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