title: Theoretical repeatability coefficient of a 100 mm visual analog scale in children.
abstract: OBJECTIVE
  The aim of this study was to determine the theoretical repeatability coefficient of a 100 mm visual analog scale (VAS) in children in different circumstances.
  
  
  METHODS
  A prospective cohort study was conducted using a convenience sample of patients aged 8 to 17 years presenting to a pediatric emergency department. Patients were asked how they liked a variety of foods (surrogate for stable pain stimulus) on a 100 mm VAS with 4 different sets of questions repeated 3 times: set 1--questions at 3-minute intervals with no specific instructions other than how to complete the VAS; set 2--same format as set 1 except for the duration of the interval (1 min); set 3--same as set 1 except patients were asked to remember their answers; set 4--same as set 1 except patients were shown their previous answers. For each, the repeatability coefficient of the VAS was determined.
  
  
  RESULTS
  A total of 100 patients aged 12.1±2.4 years were enrolled. The repeatability coefficient for the questions asked at the 3-minute interval was 12 mm, whereas it was 8 mm when asked at the 1-minute interval. When asked to remember their previous answers or to reproduce them, the repeatability coefficients for the questions were 7 and 6 mm, respectively.
  
  
  CONCLUSIONS
  The conditions of the assessments influence the repeatability coefficient of the VAS. Depending on different circumstances, the repeatability coefficient in children aged 8 to 17 years varies from 6 to 12 mm on a 100 mm VAS.
authors.affiliation: *Department of Pediatrics, Division of Emergency Medicine, CHU Sainte-Justine †Department of Emergency Medicine, Hôpital du Sacré-Coeur, Université de Montréal, Montréal, QC.
authors.forename: Benoit
authors.initials: B
authors.lastname: Bailey
authors.forename: Julie
authors.initials: J
authors.lastname: Gabbay
authors.forename: Raoul
authors.initials: R
authors.lastname: Daoust
authors.forename: Jocelyn
authors.initials: J
authors.lastname: Gravel
mesh_terms: D000293:Adolescent; D002648:Child; D004636:Emergency Service, Hospital; D005260:Female; D005502:Food; D005518:Food Preferences; D006786:Hospitals, Urban; D006801:Humans; D008297:Male; D008568:Memory; D011446:Prospective Studies; D015203:Reproducibility of Results; D062606:Tertiary Care Centers; D013997:Time Factors; D064232:Visual Analog Scale