title: Use of real-time polymerase chain reaction (rtPCR) as a diagnostic tool for influenza infection in a vaccine efficacy trial.
abstract: BACKGROUND
  Conventional techniques for diagnosing influenza based on viral cell culture or disease serology have limitations, and molecular assays, such as real-time polymerase chain reaction (rtPCR) are increasingly used.
  
  
  OBJECTIVE
  To evaluate the use of rtPCR as a diagnostic tool for the determination of influenza virus infection.
  
  
  METHODS
  This prospective, double-blind, placebo-controlled, randomised efficacy study was conducted in persons aged 18-64 years. Cases of influenza-like-illness (ILI), defined as at least one systemic symptom [fever ≥37.8°C and/or myalgia] and at least one respiratory symptom [cough and/or sore throat] were identified by active and passive surveillance. For each case of suspected ILI, nasal and throat swabs were collected and analysed by viral culture and rtPCR.
  
  
  RESULTS
  227 ILI cases were positive by rtPCR while 64% (145/227) were positive by both rtPCR and culture. For both assays, the maximum percentage of swabs that tested positive was on Day 0, thereafter positive samples by rtPCR remained constant until Day 5 but decreased progressively by culture. All rtPCR positive cases with a viral load of below 4.5log(10) copies/sample were negative by culture. There were however culture negative cases with high viral loads. Vaccine efficacy for influenza was estimated as 54.7% by rtPCR (culture positive or negative) and 61.6% by culture irrespective of match to vaccine strain. Clinical severity was not significantly different between culture positive cases and culture negative but rtPCR positive cases.
  
  
  CONCLUSIONS
  rtPCR is a sensitive and specific diagnostic tool for influenza vaccine efficacy studies.
authors.affiliation: Vaccine Research Center, University of Tampere, Biokatu 10, Tampere, Finland. timo.vesikari@uta.fi
authors.forename: Timo
authors.initials: T
authors.lastname: Vesikari
authors.forename: Jiri
authors.initials: J
authors.lastname: Beran
authors.forename: Serge
authors.initials: S
authors.lastname: Durviaux
authors.forename: Isabelle
authors.initials: I
authors.lastname: Stainier
authors.forename: Mohamed
authors.initials: M
authors.lastname: El Idrissi
authors.forename: Karl
authors.initials: K
authors.lastname: Walravens
authors.forename: Jeanne-Marie
authors.initials: JM
authors.lastname: Devaster
mesh_terms: D000328:Adult; D003371:Cough / Q000821:virology; D006801:Humans; D007252:Influenza Vaccines / Q000276:immunology; D007251:Influenza, Human / Q000175:diagnosis* / Q000276:immunology / Q000821:virology; D008875:Middle Aged; D009975:Orthomyxoviridae / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity*; D010612:Pharyngitis / Q000821:virology; D016032:Randomized Controlled Trials as Topic; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods*; D012307:Risk Factors; D012680:Sensitivity and Specificity; D014611:Vaccination; D019562:Viral Load; D014776:Virus Cultivation / Q000379:methods; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines