title: Factor structure and clinical validity of competing models of positive symptoms in schizophrenia.
abstract: BACKGROUND
  The factor structure of four competing models of positive symptoms and their clinical validity was studied in a sample of 253 schizophrenia inpatients.
  
  
  METHODS
  The following models were tested using confirmatory factor analysis: a one-dimension severity model, a two-dimension model comprising a psychosis factor and a disorganization factor, a four-dimension model based on the Scale for the Assessment of Positive Symptoms (SAPS) structure in subscales, and a five-dimension model derived from the previous one by further differentiating Schneiderian delusions from non-Schneiderian ones.
  
  
  RESULTS
  More complex multifactorial models fit the data better than simpler models. The five-dimension model was the best adjusted (goodness of fit index = .844, nonnormed fit index = .812, normed fit index = .728). Whereas the one-dimension model did not display significant association with the clinical variables, multidimensional models were related to age at onset and illness severity. The two-dimension model captured well the clinical correlates of the more complex models.
  
  
  CONCLUSIONS
  None of the tested models showed good fit to the data. The one-dimension model displayed both poor factor validity and poor external validity; therefore, research relying on the SAPS total score may reach misleading conclusions.
authors.affiliation: Psychiatric Unit, Virgen del Camino Hospital, Pamplona, Spain.
authors.forename: V
authors.initials: V
authors.lastname: Peralta
authors.forename: M J
authors.initials: MJ
authors.lastname: Cuesta
mesh_terms: D000328:Adult; D017668:Age of Onset; D003072:Cognition Disorders / Q000175:diagnosis; D003702:Delusions / Q000175:diagnosis; D003937:Diagnosis, Differential; D005163:Factor Analysis, Statistical; D005260:Female; D006212:Hallucinations / Q000175:diagnosis; D006760:Hospitalization; D006801:Humans; D008297:Male; D008960:Models, Psychological; D008962:Models, Theoretical; D015999:Multivariate Analysis; D011569:Psychiatric Status Rating Scales / Q000706:statistics & numerical data*; D015203:Reproducibility of Results; D012559:Schizophrenia / Q000175:diagnosis*; D012565:Schizophrenic Psychology; D012720:Severity of Illness Index