The factor structure of the Scale for the Assessment of Negative Symptoms (SANS) was examined in a confirmatory factor analysis that used the LISREL procedure. Four models of negative symptom factors were tested in 130 hospitalized schizophrenic patients. A three-factor model of diminished expression, social dysfunction, and disorganization generated by the authors yielded a superior fit to the data relative to the two-factor model of Liddle (1987b) and a unifactorial severity model.

Keefe RSE, Harvey PD, Lenzenweger M, Apter S, Schmeidler J, Mohs RC, Davis KL. Empirical assessment of the factorial structure of clinical symptoms in schizophrenia: Negative symptoms.  Psychiatry Research, 1992; 44(2): 153-165.