The validity of the Personality Diagnostic Questionnaire-4 Narcissistic Personality Disorder scale for assessing pathological grandiosity.

Although controversy surrounds the definition and measurement of narcissism, the claim that pathological grandiosity is central to the construct generates little disagreement. Yet representations of pathological grandiosity vary across measures of narcissism, leading to conceptual confusion in the literature. The validity of a DSM-based measure of pathological narcissism, the Personality Diagnostic Questionnaire-4 Narcissistic Personality Disorder scale (PDQ-4 NPD), was evaluated in 1 clinical and 3 nonclinical samples (total N=2,391) for its ability to measure pathological grandiosity. Findings were generally supportive: average scores were higher in the clinical than nonclinical samples and the PDQ-4 NPD scale correlated most strongly with (a) other measures of NPD; (b) other DSM Cluster B personality disorders; (c) traits involving antagonism, hostility, and assertiveness; and (d) interpersonal distress and disaffiliative dominance. However, the low internal consistency of the PDQ-4 NPD scale and unexpected associations with Cluster A and obsessive-compulsive features point to potential psychometric weaknesses with this instrument. These findings are useful for evaluating the PDQ-4 NPD scale and for informing ongoing debates regarding how to define and assess pathological narcissism.