title: Identifying thresholds for classifying childhood psychiatric disorder: issues and prospects.
abstract: OBJECTIVE
  To evaluate empirically the implications of choosing different thresholds to classify conduct disorder and attention-deficit hyperactivity disorder for estimating prevalence, test-retest reliability of measurement, and informant (parent/teacher) agreement and for evaluating comorbidity and associated features of disorder.
  
  
  METHODS
  Data for the study came from problem checklist assessments done by parents and teachers of children aged 6 to 16 years (N = 1,229) selected with known probability from a general population sample and from structured interviews obtained in a stratified, random subsample (n = 251).
  
  
  RESULTS
  Estimates varied widely depending on the rationale used to set thresholds. Percent prevalence went from 0.1 to 39.2; kappa estimates of test-retest reliability went from .19 to .82. Parent-teacher agreement based on kappa went from .0 to .38. Relative odds between disorder and associated features varied twofold.
  
  
  CONCLUSIONS
  Use of different rationales to set thresholds for classifying childhood psychiatric disorder in the general population has profound implications for what we learn about the epidemiology of childhood disorder.
authors.affiliation: Department of Psychiatry, McMaster University, Hamilton, Ontario, Canada.
authors.forename: M H
authors.initials: MH
authors.lastname: Boyle
authors.forename: D R
authors.initials: DR
authors.lastname: Offord
authors.forename: Y
authors.initials: Y
authors.lastname: Racine
authors.forename: P
authors.initials: P
authors.lastname: Szatmari
authors.forename: J E
authors.initials: JE
authors.lastname: Fleming
authors.forename: M
authors.initials: M
authors.lastname: Sanford
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000145:classification* / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology; D002648:Child; D002653:Child Behavior Disorders / Q000145:classification* / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D016017:Odds Ratio; D009864:Ontario / Q000453:epidemiology; D010552:Personality Assessment / Q000706:statistics & numerical data*; D011594:Psychometrics; D015203:Reproducibility of Results; D012494:Sampling Studies; D014505:Urban Population / Q000706:statistics & numerical data