Evaluating the Construct Validity of the Norwegian Version of the Level of Personality Functioning Scale - Brief Form 2.0 in a Large Clinical Sample.

The Level of Personality Functioning - Brief Form 2.0 (LPFS-BF 2.0) is a 12-item self-report questionnaire developed to gain a quick impression of the severity of personality pathology according to the DSM-5 Alternative Model for Personality Disorders (AMPD). The current study evaluated the construct validity and reliability of the Norwegian version of the LPFS-BF 2.0 in a large clinical sample (N = 1673). Dimensionality was examined using confirmatory factor analysis and bifactor analysis followed by an analysis of distinctiveness of the subscales using the proportional reduction in mean squared error (PRMSE), and the concurrent validity was examined using correlations with self-report questionnaires and clinical interviews assessing PDs according to section II of the DSM-5. Taking the findings of the dimensionality and concurrent validity results together, we found moderate to good support for the use of total scores for the Norwegian version of the LPFS-BF 2.0. We would advise against the use of subscale scores, since the subscales provided only a small amount of reliable unique variance.