title: Effect of Disease Definition on Perceived Burden of Acute Respiratory Infections in Children: A Prospective Cohort Study Based on Symptom Diaries.
abstract: BACKGROUND
  Acute respiratory infections (ARIs) are among the most frequent childhood diseases in Western countries. Assessment of ARI episodes for research purposes is usually based on parent-administered retrospective questionnaires or prospective symptom diaries. The aim of our analysis was to compare the effect of ARI definitions on the corresponding disease burden in a prospective cohort study using symptom diaries.
  
  
  METHODS
  A literature search was performed to identify definitions of ARI used in research studies. The definitions were applied to a symptom diary dataset from a cohort study of 1-3-year-old children conducted in the winter season 2013/2014. We compared the total number of ARI episodes, the total number of days with ARI and the median and mean duration of ARI episodes resulting from the use of the different definitions.
  
  
  RESULTS
  Six ARI definitions were identified in the literature. Depending on ARI definition, the total number of ARI episodes and the total number of days with ARI in our dataset varied by a factor of 1.69 and 1.53, respectively, between the lowest and the highest. The median duration of the episodes ranged from 7 to 10 days.
  
  
  CONCLUSIONS
  Different definitions led to considerable differences in the number and duration of ARI episodes, making direct comparisons of studies with different methods questionable. We propose the use of a standardized ARI definition in upcoming cohort studies working with diary data. This process could be conducted using a Delphi survey with experts in this study field.
authors.affiliation: From the *ESME - Epidemiological and Statistical Methods Research Group, Helmholtz Centre for Infection Research, Braunschweig, Germany; †PhD Programme "Epidemiology," Braunschweig-Hannover, Germany; ‡German Centre for Infection Research (DZIF), Hannover-Braunschweig site, Braunschweig, Germany; §Hannover Medical School (MHH), Hannover, Germany; and ¶Institute for Medical Epidemiology, Biometry, and Informatics (IMEBI), Medical Faculty of the Martin Luther University Halle-Wittenberg, Halle, Germany.
authors.forename: Beate
authors.initials: B
authors.lastname: Zoch
authors.forename: Annette
authors.initials: A
authors.lastname: Günther
authors.forename: André
authors.initials: A
authors.lastname: Karch
authors.forename: Rafael
authors.initials: R
authors.lastname: Mikolajczyk
mesh_terms: D000208:Acute Disease / Q000453:epidemiology; D002675:Child, Preschool; D006801:Humans; D007223:Infant; D008499:Medical Records; D011446:Prospective Studies; D012141:Respiratory Tract Infections / Q000175:diagnosis* / Q000453:epidemiology*