title: Comparison of clinical presentation and laboratory values at admission between PCR-confirmed influenza A H1N1 infection and influenza-like disease, South-East Austria.
abstract: OBJECTIVE
  Reliable and rapid diagnosis of influenza A H1N1 is essential to initiate the appropriate antiviral therapy and preventive measures. As PCR assays are time-consuming and rapid antigen tests have a limited sensitivity, official influenza case definitions are used in many clinical settings. These, however, are based exclusively on clinical criteria and have only a moderate potential to differentiate between influenza and other febrile diseases. Only limited data on the differences in clinical and laboratory parameters between influenza and non-influenza febrile diseases are available to date.
  
  
  METHODS
  This was a retrospective case-negative control series that was conducted in Styria, southeast Austria. We analyzed the differences in clinical presentation and laboratory admission parameters between patients with PCR-confirmed H1N1 influenza infection (n = 199) and those with influenza-like disease and negative influenza PCR results (ILD group; n = 252).
  
  
  RESULTS
  In the multivariable analysis lower C-reactive protein (CRP) level, lower white blood cell (WBC) count, fever, wheezing, cough, and the absence of nausea or sudden onset remained significant predictors of H1N1 influenza in adult patients (n = 263). Lower CRP level, lower WBC count, and cough remained significant predictors in pediatric patients (<16 years; n = 188).
  
  
  CONCLUSIONS
  Lower CRP level, lower WBC count, and cough were significant predictors of H1N1 in both the adult and pediatric patient group. These data may help to develop an improved case definition for suspected H1N1 infection which combines clinical findings and easily available laboratory parameters.
authors.affiliation: Division of Pulmonology, Medical University of Graz, Auenbruggerplatz 15, 8036, Graz, Austria, martin.hoenigl@medunigraz.at.
authors.forename: M
authors.initials: M
authors.lastname: Hoenigl
authors.forename: J
authors.initials: J
authors.lastname: Prattes
authors.forename: M
authors.initials: M
authors.lastname: Drescher
authors.forename: K
authors.initials: K
authors.lastname: Tovilo
authors.forename: K
authors.initials: K
authors.lastname: Seeber
authors.forename: H H
authors.initials: HH
authors.lastname: Kessler
authors.forename: K
authors.initials: K
authors.lastname: Vander
authors.forename: M
authors.initials: M
authors.lastname: Palfner
authors.forename: M
authors.initials: M
authors.lastname: Meilinger
authors.forename: A
authors.initials: A
authors.lastname: Avian
authors.forename: T
authors.initials: T
authors.lastname: Valentin
authors.forename: I
authors.initials: I
authors.lastname: Zollner-Schwetz
authors.forename: V
authors.initials: V
authors.lastname: Strenger
authors.forename: R
authors.initials: R
authors.lastname: Krause
authors.forename: H
authors.initials: H
authors.lastname: Flick
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001317:Austria; D016022:Case-Control Studies; D005260:Female; D006760:Hospitalization; D006801:Humans; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000821:virology*; D008297:Male; D015999:Multivariate Analysis; D016133:Polymerase Chain Reaction; D012189:Retrospective Studies; D055815:Young Adult