Objective:

The present study aims to establish a clinical cut-off for the Grandiosity dimension, using item-level evaluation procedures.

Methods:

Participants were 5,387 adults, including outpatients diagnosed with narcissistic personality disorder (NPD), outpatients diagnosed with other personality disorders, and adults from the community. We administered the self-reported Grandiosity scale from the Dimensional Clinical Personality Inventory 2 (IDCP-2). The equating procedure was applied to generate theta scores for participants who did not answer all items.

Results:

The Wright map revealed that outpatients scored high on the latent continuum of the Grandiosity scale. Group comparison showed large effect sizes for the mean difference between patients and non-patients. The ROC curve supports a cut off at a -0.45 score in theta standardisation, which yields a high sensitivity (91%) and moderate specificity (58%). Moreover, the PPP (71%) and NPP (79%) values suggest that the scale is able to identify NPD patients in 71% of cases, and people without NPD in 79% of cases.

Conclusions:

The findings suggest the IDCP-2 Grandiosity scale is useful as an NPD screening tool. Possible clinical applications for the scale are described and the limitations of the study are discussed.

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