title: Identification of influenza A virus by shell vial culture and two commercially available antigen detection methods.
abstract: BACKGROUND
  Effective use of amantidine and rimantidine for treating patients and for reducing transmission requires rapid diagnosis of influenza A. Rapid culture methods require 1-2 days to detect influenza A virus. Direct fluorescent antibody (DFA) staining and enzyme immunoassay (EIA) can detect influenza A antigen within 1-4 h.
  
  
  OBJECTIVE
  We compared DFA staining using the Bartels viral respiratory panel and the Directigen FLU-A EIA with shell vial centrifugation culture.
  
  
  METHODS
  Ninety-seven fresh specimens from a variety of respiratory sources and transported from hospitals throughout the USA to our national referral laboratory were tested. A true positive was defined as culture positive or both antigen tests positive.
  
  
  RESULTS
  Fifteen specimens were true positive. Sensitivity with culture was 93%, EIA 67%, and DFA 47%. Specificity was excellent with all three methods: 100%, 98%, 99%. Culture detected additional viruses that can cause respiratory tract disease: herpes simplex, cytomegalovirus, respiratory syncytial, influenza B, and adenovirus. Fourteen (70%) of 20 frozen specimens previously positive for influenza A were positive on retest by EIA. Overall sensitivity of EIA compared with culture using 35 positive specimens was 69%.
  
  
  CONCLUSIONS
  These results suggest that the rapid EIA is useful to screen for influenza A, but that critical antigen-negative specimens should be submitted to a virology laboratory for culture for optimal sensitivity and for recovery of other viruses.
authors.affiliation: Diagnostic Virology Laboratory, Associated Regional and University Pathologists, Inc., Salt Lake City, UT 84108, USA.
authors.forename: L L
authors.initials: LL
authors.lastname: Steed
authors.forename: V C
authors.initials: VC
authors.lastname: Salmon
authors.forename: J C
authors.initials: JC
authors.lastname: Overall