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.


CONCLUSIONS
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.
Department of Emergency Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232-4700, USA. wesley.self@vanderbilt.edu
Wesley H
WH
Self
Candace D
CD
McNaughton
Carlos G
CG
Grijalva
Yuwei
Y
Zhu
James D
JD
Chappell
John V
JV
Williams
H Keipp
HK
Talbot
David K
DK
Shay
Marie R
MR
Griffin
D000293:Adolescent; D000328:Adult; D000956:Antigens, Viral / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D002846:Chromatography, Affinity / Q000592:standards; D003430:Cross-Sectional Studies; D004636:Emergency Service, Hospital; D005260:Female; D006801:Humans; D009980:Influenza A virus / Q000276:immunology; D009981:Influenza B virus / Q000276:immunology; D007251:Influenza, Human / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D060888:Real-Time Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D055815:Young Adult
D000956:Antigens, Viral