title: Bacterial superinfection in upper respiratory tract infections estimated by increases in CRP values: a diagnostic follow-up in primary care.
abstract: OBJECTIVE
  The aim of this study was to estimate the rate of bacterial superinfection in patients with URTI by using on-site determination of C-reactive protein (CRP).
  
  
  METHODS
  A prospective cohort study.
  
  
  METHODS
  A total of 30 primary care practices.
  
  
  METHODS
  Patients with URTI.
  
  
  METHODS
  The CRP value was determined at the first consultation and at a follow-up within 3-5 days. CRP values of 30 units (mg) or higher were considered to be an indication of bacterial involvement.
  
  
  METHODS
  CRP values during follow-up and duration of illness.
  
  
  RESULTS
  Among the 506 patients included, 73.1% exhibited a CRP value below the defined limit at their first visit and were considered to suffer from URTI of viral origin. The rate of subsequent bacterial superinfection was 8.1%. Compared with patients suffering from URTI of bacterial or viral origin the duration of illness in patients with bacterial superinfection was significantly longer.
  
  
  CONCLUSIONS
  During follow-up of patients with URTI, the prevalence of bacterial superinfection detected by using a near patient CRP determination is surprisingly low. This result should help to reduce the prescription rate of antibiotics in primary care.
authors.affiliation: Department of General Practice and Family Medicine, Medical University, Vienna, Austria. heide.lingard@meduniwien.ac.at
authors.forename: Heide
authors.initials: H
authors.lastname: Lingard
authors.forename: Sonja
authors.initials: S
authors.lastname: Zehetmayer
authors.forename: Manfred
authors.initials: M
authors.lastname: Maier
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002097:C-Reactive Protein / Q000032:analysis*; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012141:Respiratory Tract Infections / Q000097:blood / Q000175:diagnosis* / Q000382:microbiology; D015163:Superinfection / Q000097:blood / Q000175:diagnosis* / Q000382:microbiology
chemical_list: D002097:C-Reactive Protein