title: The Specific Level of Functioning Scale: construct validity, internal consistency and factor structure in a large Italian sample of people with schizophrenia living in the community.
abstract: BACKGROUND
  The study aimed to assess the construct validity, internal consistency and factor structure of the Specific Levels of Functioning Scale (SLOF), a multidimensional instrument assessing real life functioning.
  
  
  METHODS
  The study was carried out in 895 Italian people with schizophrenia, all living in the community and attending the outpatient units of 26 university psychiatric clinics and/or community mental health departments. The construct validity of the SLOF was analyzed by means of the multitrait-multimethod approach, using the Personal and Social Performance (PSP) Scale as the gold standard. The factor structure of the SLOF was examined using both an exploratory principal component analysis and a confirmatory factor analysis.
  
  
  RESULTS
  The six factors identified using exploratory principal component analysis explained 57.1% of the item variance. The examination of the multitrait-multimethod matrix revealed that the SLOF factors had high correlations with PSP factors measuring the same constructs and low correlations with PSP factors measuring different constructs. The confirmatory factor analysis (CFA) corroborated the 6-factor structure reported in the original validation study. Loadings were all significant and ranged from a minimum of 0.299 to a maximum of 0.803. The CFA model was adequately powered and had satisfactory goodness of fit indices (comparative fit index=0.927, Tucker-Lewis index=0.920 and root mean square error of approximation=0.047, 95% CI 0.045-0.049).
  
  
  CONCLUSIONS
  The present study confirms, in a large sample of Italian people with schizophrenia living in the community, that the SLOF is a reliable and valid instrument for the assessment of social functioning. It has good construct validity and internal consistency, and a well-defined factor structure.
authors.affiliation: Department of Psychiatry, University of Naples SUN, Naples, Italy.
authors.forename: Armida
authors.initials: A
authors.lastname: Mucci
authors.affiliation: Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Rucci
authors.affiliation: Department of Neuroscience, University of Turin, Turin, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Rocca
authors.affiliation: Department of Psychiatry, University of Naples SUN, Naples, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Bucci
authors.affiliation: Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy.
authors.forename: Dino
authors.initials: D
authors.lastname: Gibertoni
authors.affiliation: Department of Psychiatry, University of Naples SUN, Naples, Italy.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Merlotti
authors.affiliation: Department of Psychiatry, University of Naples SUN, Naples, Italy. Electronic address: silvana.galderisi@gmail.com.
authors.forename: Silvana
authors.initials: S
authors.lastname: Galderisi
authors.affiliation: Department of Psychiatry, University of Naples SUN, Naples, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Maj
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D005260:Female; D006801:Humans; D007558:Italy; D008297:Male; D008875:Middle Aged; D010551:Personality; D015203:Reproducibility of Results; D012111:Residence Characteristics; D012559:Schizophrenia / Q000175:diagnosis*; D012565:Schizophrenic Psychology; D012919:Social Behavior; D013223:Statistics as Topic
keywords: Factor structure; Personal and Social Performance Scale; Real-life functioning; Schizophrenia; Specific Level of Functioning Scale; Validation