title: Validity of a clinical model to predict influenza in patients presenting with symptoms of lower respiratory tract infection in primary care.
abstract: BACKGROUND
  Valid clinical predictors of influenza in patients presenting with lower respiratory tract infection (LRTI) symptoms would provide adequate patient information and reassurance.
  
  
  OBJECTIVE
  Assessing the validity of an existing diagnostic model (Flu Score) to detect influenza in LRTI patients.
  
  
  METHODS
  A European diagnostic study recruited 1801 adult primary care patients with LRTI-like symptoms existing ≤7 days between October and April 2007-2010.
  
  
  METHODS
  History and physical examination findings were recorded and nasopharyngeal swabs taken. Polymerase chain reaction (PCR) for influenza A/B was performed as reference test. Diagnostic accuracy of the Flu Score (1× onset <48 hours + 2× myalgia + 1× chills or sweats + 2× fever and cough) was expressed as area under the curve (AUC), calibration slopes and likelihood ratios (LRs).
  
  
  RESULTS
  A total of 273 patients (15%) had influenza on PCR. The AUC of the Flu Score during winter months was 0.66 [95% CI (95% confidence internal) 0.63-0.70]. During peak influenza season, both influenza prevalence (24%) and AUC were higher [0.71 (95% CI 0.66-0.76], but calibration remained poor. The Flu Score assigned 64% of the patients as 'low-risk' (10% had influenza, LR - 0.6). About 12% were classified as 'high risk' of whom 32% had influenza (LR + 2.7). During peak influenza season, 60% and 14% of patients were classified as low and high risk, respectively, with influenza prevalences being 14% (LR - 0.5) and 50% (LR + 3.2).
  
  
  CONCLUSIONS
  The Flu-Score attributes a small subgroup of patients with a high influenza risk (prevalence 32%). However, clinical usefulness is limited because this group is small and the association between predicted and observed risks is poor. Considerable diagnostic imprecision remains when it comes to differentiating those with influenza on clinical grounds from the many other causes of LRTI in primary care. New point of care tests are required that accurately, rapidly and cost effectively detect influenza in patients with respiratory tract symptoms in primary care.
authors.affiliation: University Medical Center Utrecht, Julius Center for Health Sciences and Primary Care, Utrecht, The Netherlands, s.f.vanvugt@umcutrecht.nl.
authors.forename: Saskia F
authors.initials: SF
authors.lastname: van Vugt
authors.affiliation: University Medical Center Utrecht, Julius Center for Health Sciences and Primary Care, Utrecht, The Netherlands.
authors.forename: Berna Dl
authors.initials: BD
authors.lastname: Broekhuizen
authors.affiliation: University Medical Center Utrecht, Julius Center for Health Sciences and Primary Care, Utrecht, The Netherlands.
authors.forename: Nicolaas Pa
authors.initials: NP
authors.lastname: Zuithoff
authors.affiliation: University Medical Center Utrecht, Julius Center for Health Sciences and Primary Care, Utrecht, The Netherlands.
authors.forename: Gerrit A
authors.initials: GA
authors.lastname: van Essen
authors.affiliation: Department of Epidemiology and Biostatistics, University of Georgia, College of Public Health, Athens, GA, USA.
authors.forename: Mark H
authors.initials: MH
authors.lastname: Ebell
authors.affiliation: Centre for General Practice, University of Antwerp and Laboratory of Medical Microbiology, Vaccine & Infectious Disease Institute (VAXINFECTIO), Antwerp, Belgium.
authors.forename: Samuel
authors.initials: S
authors.lastname: Coenen
authors.affiliation: Laboratory of Medical Microbiology, Vaccine & Infectious Disease Institute (VAXINFECTIO), Antwerp, Belgium.
authors.forename: Margareta
authors.initials: M
authors.lastname: Ieven
authors.affiliation: Laboratory of Medical Microbiology, Vaccine & Infectious Disease Institute (VAXINFECTIO), Antwerp, Belgium.
authors.forename: Christine
authors.initials: C
authors.lastname: Lammens
authors.affiliation: Laboratory of Medical Microbiology, Vaccine & Infectious Disease Institute (VAXINFECTIO), Antwerp, Belgium.
authors.forename: Herman
authors.initials: H
authors.lastname: Goossens
authors.affiliation: Institute of Primary Care and Public Health, Cardiff University, School of Medicine, and.
authors.forename: Chris C
authors.initials: CC
authors.lastname: Butler
authors.affiliation: Institute of Translation, Innovation, Methodology and Engagement, Cardiff, UK, and.
authors.forename: Kerenza
authors.initials: K
authors.lastname: Hood
authors.affiliation: University of Southampton, FMedSci FRCGP Primary Care and Population Sciences Unit, Faculty of Medicine, Southampton, UK.
authors.forename: Paul
authors.initials: P
authors.lastname: Little
authors.affiliation: University Medical Center Utrecht, Julius Center for Health Sciences and Primary Care, Utrecht, The Netherlands.
authors.forename: Theo Jm
authors.initials: TJ
authors.lastname: Verheij
mesh_terms: D000328:Adult; D019540:Area Under Curve; D003371:Cough; D003430:Cross-Sectional Studies; D005060:Europe; D005260:Female; D005334:Fever; D006801:Humans; D009980:Influenza A virus; D009981:Influenza B virus; D007251:Influenza, Human / Q000175:diagnosis* / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011320:Primary Health Care; D063189:Symptom Assessment / Q000379:methods*; D055815:Young Adult
keywords: Cough; Europe; diagnostic accuracy; influenza; lower respiratory tract infection; primary health care.