"Green et al. Paranoid Thoughts Scale-revised": Structural invariance and clinical utility of a brief version in schizophrenia

Abstract

Objective: Persecutory ideas are highly frequent in psychotic disorders and particularly in schizophrenia. Although several measures exist to assess persecutory ideas in both clinical and non-clinical samples, there is a need for brief and psychometrically sound measures to capture the multidimensional aspects of paranoia in people diagnosed with schizophrenia. Our aim was to validate a brief version of the revised Green et al., Paranoid Thoughts Scale (R-GPTS) in schizophrenia in order to minimize time-consuming assessment.

Methods: 100 individuals with schizophrenia and 72 non-clinical controls were recruited. We used the GPTS-8, a brief 8-item version of the R-GPTS recently developed and validated in the French general population. Psychometric properties of the scale were investigated including its factor structure, internal consistency, and convergent/divergent validities.

Results: Confirmatory factor analysis supported the original two-factor structure (social reference and persecution subscales) of the GPTS-8. The GPTS-8 was positively and moderately correlated with the Positive and Negative Syndrome Scale (PANSS) suspiciousness item indicating good internal consistency. Concerning divergent validity, no correlations were found between the GPTS-8 and the Montreal cognitive assessment (MoCA). Importantly patients with schizophrenia reported higher scores on the GTPS-8 than controls demonstrating its clinical validity.

Conclusions: The French GPTS 8-item brief scale-8 retains the psychometric strengths of the R-GPTS in schizophrenia with relevant clinical validity. The GPTS-8 can consequently be used as a short and quick measure of paranoid ideations in individuals with a diagnosis of schizophrenia.

Keywords: Brief version; Paranoia; Schizophrenia; Self-assessment.