title: Clinical diagnosis of influenza virus infection: evaluation of diagnostic tools in general practice.
abstract: BACKGROUND
  With the development of new antiviral agents for influenza, the urge for rapid and reliable diagnosis of influenza becomes increasingly important. Respiratory virus infections are difficult to distinguish on clinical grounds. General practitioners (GPs) however, still depend on their clinical judgement.
  
  
  OBJECTIVE
  To evaluate the importance of clinical symptoms in the diagnosis of influenza virus infection.
  
  
  METHODS
  A multicentre questionnaire study.
  
  
  METHODS
  Eighty-one patients from 14 general practices.
  
  
  METHODS
  Patients with fever and at least one constitutional symptom and one respiratory symptom were included. A questionnaire with the medical history and clinical symptoms was completed and a combined nose-throat swab was taken. Virus culture, rapid culture, and polymerase chain reaction (PCR) amplification were performed on each specimen. Multivariate analysis was used to obtain the best predictive model.
  
  
  RESULTS
  By using PCR, an increase was seen in the detection of the viral pathogens compared with the results of culture. In 42 out of 81 patients PCR was positive for influenza. A positive predictive value (PPV) of 75% was observed for the combination of headache at onset, feverishness at onset, cough, and vaccination status during the period of increase influenza activity. Criteria used by the ICHPPC-2 resulted in a PPV of 54%. The PPV for diagnosis made by the GP was 76%.
  
  
  CONCLUSIONS
  Although influenza is difficult to diagnose on clinical grounds, the GPs in this study were able to diagnose influenza as such more accurately on their judgement than by the other criteria.
authors.affiliation: Department of Virology, Eijkman-Winkler Institute for Microbiology, Infectious Diseases and Inflammation, The Netherlands. L.Elden@zkh-eemland.nl
authors.forename: L J
authors.initials: LJ
authors.lastname: van Elden
authors.forename: G A
authors.initials: GA
authors.lastname: van Essen
authors.forename: C A
authors.initials: CA
authors.lastname: Boucher
authors.forename: A M
authors.initials: AM
authors.lastname: van Loon
authors.forename: M
authors.initials: M
authors.lastname: Nijhuis
authors.forename: P
authors.initials: P
authors.lastname: Schipper
authors.forename: T J
authors.initials: TJ
authors.lastname: Verheij
authors.forename: I M
authors.initials: IM
authors.lastname: Hoepelman
mesh_terms: D000328:Adult; D000368:Aged; D002983:Clinical Competence; D005194:Family Practice / Q000592:standards; D005260:Female; D006801:Humans; D007251:Influenza, Human / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016133:Polymerase Chain Reaction; D011237:Predictive Value of Tests; D011795:Surveys and Questionnaires; D014773:Virology / Q000379:methods*