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
Armida Mucci, Paola Rucci, Paola Rocca, Paola Bucci, Dino Gibertoni, Eleonora Merlotti, Silvana Galderisi, Mario Maj, Italian Network for Research on Psychoses, Marcello Chieffi, Mario Luciano, Giuseppe Piegari, Ernesta Plaitano, Gaia Sampogna, Alessandro Bertolino, Raffaele Salfi, Luca Gheda, Federica Pinna, Maria Signorelli, Tiziano Acciavatti, Carlo Faravelli, Stefano Pallanti, Mario Altamura, Pietro Calcagno, Gabriella Di Emidio, Rita Roncone, Lucio Oldani, Andrea De Bartolomeis, Carla Gramaglia, Elena Tenconi, Carlo Marchesi, Claudio Cargioli, Liliana Dell'Osso, Fabio Di Fabio, Paolo Girardi, Giorgio Di Lorenzo, Palmiero Monteleone, Simone Bolognesi, Cristiana Montemagni, Armida Mucci, Paola Rucci, Paola Rocca, Paola Bucci, Dino Gibertoni, Eleonora Merlotti, Silvana Galderisi, Mario Maj, Italian Network for Research on Psychoses, Marcello Chieffi, Mario Luciano, Giuseppe Piegari, Ernesta Plaitano, Gaia Sampogna, Alessandro Bertolino, Raffaele Salfi, Luca Gheda, Federica Pinna, Maria Signorelli, Tiziano Acciavatti, Carlo Faravelli, Stefano Pallanti, Mario Altamura, Pietro Calcagno, Gabriella Di Emidio, Rita Roncone, Lucio Oldani, Andrea De Bartolomeis, Carla Gramaglia, Elena Tenconi, Carlo Marchesi, Claudio Cargioli, Liliana Dell'Osso, Fabio Di Fabio, Paolo Girardi, Giorgio Di Lorenzo, Palmiero Monteleone, Simone Bolognesi, Cristiana Montemagni
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).
Conclusion: 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.
Keywords: Factor structure; Personal and Social Performance Scale; Real-life functioning; Schizophrenia; Specific Level of Functioning Scale; Validation.
Copyright © 2014 Elsevier B.V. All rights reserved.
Source: PubMed