Diagnostic Utility and Measurement Invariance of the Revised Green Paranoid Thoughts Scale Across Age, Gender, and Clinical Status

Abstract: The Revised Green Paranoid Thoughts Scale (R-GPTS) is a widely used instrument to evaluate the severity of paranoid thinking; however, its psychometric and diagnostic properties remain insufficiently explored, particularly outside Western contexts. This study aimed to evaluate the psychometric properties of the R-GPTS, including its structural validity; measurement invariance across gender, age, and clinical status; convergent and criterion validity; and its diagnostic performance using clinician-verified samples and symptom measures. The sample included 629 participants: nonclinical controls ( n = 395), individuals with psychiatrist-confirmed schizophrenia spectrum disorders ( n = 116), and participants with other psychiatrist-confirmed diagnoses ( n = 118). The original two-factor model showed excellent fit, and scalar measurement invariance was supported across demographic and clinical groups. Regarding latent group differences, younger participants reported higher scores on ideas of reference, while men reported greater persecution scores. The clinical groups scored significantly higher than controls on persecutory and referential thinking, with the highest persecution levels observed in the psychosis group, confirming criterion validity. The Persecution subscale demonstrated moderate diagnostic accuracy (AUC = 0.84–0.88), and the Ideas of Reference subscale showed fair accuracy (AUC = 0.75–0.81). The R-GPTS subscales correlated in the expected direction with other measures of relevant constructs, supporting its concurrent validity.