title: Is the interpretation of rapid antigen testing for respiratory syncytial virus as simple as positive or negative?
abstract: OBJECTIVE
  To measure the performance characteristics of an immunochromatographic rapid antigen test for respiratory syncytial virus (RSV) and determine how its interpretation should be contextualised in patients presenting to the emergency department (ED) with bronchiolitis.
  
  
  METHODS
  Diagnostic accuracy study of a rapid RSV test.
  
  
  METHODS
  County hospital ED.
  
  
  METHODS
  We took paired nasal samples from consecutively enrolled infants with bronchiolitis and tested them with a rapid immunochromatographic antigen test and reverse transcriptase PCR gold standard.
  
  
  METHODS
  Sensitivity, specificity, the effect of point prevalence, clinical findings and overall context on predictive values. We used these to construct a graphical contextual model to show how the results of RSV antigen tests from infants presenting within 24 h should influence interpretation of subsequent antigen tests.
  
  
  RESULTS
  We analysed 607 patients. The sensitivity and specificity for immunochromatographic testing was 79.4% (95% CI 73.9% to 84.2%) and 67.1% (95% CI 61.9% to 72%) respectively. We found little evidence of spectrum bias. In our contextual model the best predictor of a positive RT-PCR test was a positive antigen test OR 5.47 (95% CI 3.65 to 8.18) and the number of other infants having positive tests within 24 h OR 1.48 (95% CI 1.26 to 1.72) per infant. Increasing numbers presenting to the ED with bronchiolitis in a given day increases the probability of RSV infection.
  
  
  CONCLUSIONS
  The RSV antigen test we examined had modest performance characteristics. The results of the antigen test should be interpreted in the context of the results of previous tests.
authors: Department of Emergency Medicine, University of California Davis, , Sacramento, California, USA.
authors: Paul
authors: P
authors: Walsh
authors: Christina
authors: C
authors: Overmyer
authors: Christine
authors: C
authors: Hancock
authors: Jacquelyn
authors: J
authors: Heffner
authors: Nicholas
authors: N
authors: Walker
authors: Thienphuc
authors: T
authors: Nguyen
authors: Lucas
authors: L
authors: Shanholtzer
authors: Enrique
authors: E
authors: Caldera
authors: James
authors: J
authors: Pusavat
authors: Eli
authors: E
authors: Mordechai
authors: Martin E
authors: ME
authors: Adelson
authors: Kathryn T
authors: KT
authors: Iacono
mesh_terms: D000956:Antigens, Viral / Q000097:blood*; D001990:Bronchiolitis, Viral / Q000175:diagnosis*; D002846:Chromatography, Affinity / Q000379:methods* / Q000592:standards; D004636:Emergency Service, Hospital; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D009305:Nasopharynx / Q000821:virology; D011933:Reagent Kits, Diagnostic / Q000592:standards; D018357:Respiratory Syncytial Virus Infections / Q000175:diagnosis*; D012136:Respiratory Syncytial Viruses / Q000276:immunology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity
chemical_list: D000956:Antigens, Viral; D011933:Reagent Kits, Diagnostic
keywords: Infectious Diseases; Paediatrics; Respiratory, Pneumonia/Infections; Statistics; Viral
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