Factor structure and clinical validity of competing models of positive symptoms in schizophrenia

Biol Psychiatry. 1998 Jul 15;44(2):107-14. doi: 10.1016/s0006-3223(97)00341-7.

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.

Conclusion: 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.

MeSH terms

  • Adult
  • Age of Onset
  • Cognition Disorders / diagnosis
  • Delusions / diagnosis
  • Diagnosis, Differential
  • Factor Analysis, Statistical
  • Female
  • Hallucinations / diagnosis
  • Hospitalization
  • Humans
  • Male
  • Models, Psychological
  • Models, Theoretical
  • Multivariate Analysis
  • Psychiatric Status Rating Scales / statistics & numerical data*
  • Reproducibility of Results
  • Schizophrenia / diagnosis*
  • Schizophrenic Psychology*
  • Severity of Illness Index