title: The predictive validity of a diagnosis of schizophrenia. A report from the International Study of Schizophrenia (ISoS) coordinated by the World Health Organization and the Department of Psychiatry, University of Nottingham.
abstract: BACKGROUND
  Outcome is important in the validation of psychiatric diagnosis, as most disorders lack clinicopathological correlates. We describe the predictive validity of four definitions of schizophrenia (DSM-III-R, ICD-10, ICD-9 and CATEGO S+), in a representative cohort of patients selected during their first episode of psychosis.
  
  
  METHODS
  Each definition of schizophrenia was applied to 99 patients. Their respective ability to predict 13-year outcome (Global Assessment of Functioning scales) was assessed.
  
  
  RESULTS
  DSM-III-R and ICD-10 diagnoses of schizophrenia have high predictive validity for long-term outcome, and both provide relatively stable diagnoses. ICD-9 is reasonably good at predicting disability, but not symptoms, and CATEGO S+ showed no predictive validity. Adding six-month duration criteria to ICD-10, ICD-9 and CATEGO S+ improved their predictive validity, and removing the six-month duration criterion from DSM-III-R commensurately reduced predictive validity.
  
  
  CONCLUSIONS
  Modern diagnostic systems (DSM-III-R and ICD-10) have high predictive validity, and are superior to ICD-9. The six-month duration criterion of DSM-III-R schizophrenia accounts for its predictive validity and stability over 13 years, but restricts its use in first-episode studies. The one-month duration criterion of ICD-10 is less restrictive, without major compromises in predictive validity or stability.
authors.affiliation: Department of Psychiatry, Royal Liverpool University Hospital.
authors.forename: P
authors.initials: P
authors.lastname: Mason
authors.forename: G
authors.initials: G
authors.lastname: Harrison
authors.forename: T
authors.initials: T
authors.lastname: Croudace
authors.forename: C
authors.initials: C
authors.lastname: Glazebrook
authors.forename: I
authors.initials: I
authors.lastname: Medley
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D011237:Predictive Value of Tests; D011379:Prognosis; D011569:Psychiatric Status Rating Scales; D015203:Reproducibility of Results; D012559:Schizophrenia / Q000175:diagnosis*; D012680:Sensitivity and Specificity