Adaptation and validation of the Spanish version of the Strauss and Carpenter Prognostic Scale for Schizophrenia

Abstract

Introduction: The aim of this study was to validate the Spanish version of the Strauss and Carpenter Prognostic Scale for Schizophrenia (Strauss and Carpenter, 1977).

Method: We performed a multicenter, longitudinal, descriptive study. Forward and backtranslation of the original scale was performed. The sample was composed of persons diagnosed with schizophrenia aged between 18 and 65 years. We calculated interrater reliability, construct validity according to the Global Assessment Scale (GAS), Satisfaction with Life Domains Scale (SLDS), the Global Clinical Impression-Schizophrenia (GCI) scale, The World Health. Organization Short Disability Assessment Schedule (WHO-DAS) and the Positive and Negative Syndrome Scale (PANSS), and predictive validity at the 1-year follow-up using three criterion measures of the GCI, WHO-DAS and GAS scales.

Results: The internal consistency coefficient (Cronbach's alpha) was 0.70. The intraclass correlation coefficient ranged from 0.54 to 0.99, except for item 5 (resources for the current treatment), which was -0.13. The correlation between the distinct scales (measuring construct validity) was significant, with a p-value of < 0.01, except for the SLDS, which showed a higher p-value (p<0.05). The Strauss-Carpenter score correlated with all three scores at 1 year (GCI, GAS and WHO-DAS) with an alpha of less than 0.01, showing good predictive validity.

Conclusions: The Spanish adaptation of the Strauss and Carpenter prognostic scale is reliable and valid and allows a more severe disease course to be predicted.