Validation of the Spanish Personal and Social Performance scale (PSP) in outpatients with stable and unstable schizophrenia.

INTRODUCTION: The main long-term therapeutic goals of schizophrenia should go beyond the symptoms and include the improvement of patients' psychosocial functioning and quality of life. The aim of this study was to validate the Personal and Social Performance (PSP) scale in Spanish outpatients with schizophrenia.
MATERIALS AND METHODS: Naturalistic, 6-month follow-up, multicentre study. 244 patients and 76 controls were evaluated using the PSP, the Social and Occupational Functioning Assessment Scale (SOFAS), and the Clinical Global Impression - Severity (CGI-S) and Change (CGI-C) scales.
RESULTS: Internal reliability=0.87. Test-retest reliability=0.98. Construct validity=1 component that explained 73.2% of the variance. Convergent validity: Pearson correlation coefficient between PSP and SOFAS=0.95 (p<0.0001), between PSP and CGI-S=-0.88 (p<0.0001). Discriminant validity: the PSP discriminates between patients and controls [50.3 versus 91.9, p<0.0001] and among patients with mild, moderate, and severe schizophrenia according to CGI-S scores [73 versus 56.6 versus 37.5, p<0.0001]. Area under the curve=0.986. A cut-off point of 79 on the PSP scale provided good sensitivity (94.3%) and specificity (96.1%) for identifying patients and controls according to their level of functioning. At month 6 significant improvements (p<0.0001) were seen in PSP, SOFAS, and CGI-C scores. The PSP was sensitive to improvement; a score of very much improved in the CGI-C corresponds to a improvement of 34 points in the PSP.
CONCLUSION: The Spanish PSP is a reliable, valid and sensitive instrument for measuring functioning in outpatients with schizophrenia. As a brief, clinician-rated instrument, the PSP scale seems to be appropriate for use in everyday clinical practice as a mean of identifying and monitoring changes in patient's functioning.