Is research using the narcissistic personality inventory relevant for understanding narcissistic personality disorder?

Most research on narcissism has been conducted using the narcissistic personality inventory (NPI). However, the generalizability of findings from the NPI to narcissistic personality disorder (NPD) is unknown. The current study uses two samples (48 clinical outpatients; 49 undergraduates) to address this question by examining the correlations between the NPI and interview ratings of NPD. The profiles generated by both assessments in relation to measures of general personality traits are compared to expert and meta-analytically derived profiles of NPD. The NPI and NPD assess overlapping constructs as they are significantly correlated and generate similar personality profiles. The measures diverge primarily in that NPI narcissism includes traits related to certain facets of Extraversion, which is consistent with expert conceptualizations of NPD.