Psychometric Evaluation and Refinement of the Level of Personality Functioning Scale-Self Report: Development of the...

The DSM-5 Alternative Model for Personality Disorders (AMPD) provides a dimensional framework for assessing personality dysfunction, and the Level of Personality Functioning Scale-Self Report (LPFS-SR) is a widely used instrument for evaluating the construct. However, its psychometric properties and practical feasibility remain areas of concern due to its extensive item length and structural misspecification. A sample of 344 participants was recruited to assess the psychometric properties of the LPFS-SR using bifactor modeling and item response theory (IRT) analyses. We replicated general factor loadings from previous studies and identified that items describing milder dysfunctions were misaligned with the latent construct due to lower discrimination parameters. Items with a larger number of words also exhibited lower measurement quality. A stepwise and Ant Colony Optimization (ACO) derived two abbreviated item sets. Based on psychometric evaluation, items were selected with optimal factor loadings, discrimination parameters, and balanced severity thresholds. The two finalized short forms demonstrated preserved internal consistency, and their total score correlated highly with the original scale. Convergent and criterion validity indicated significant associations of the short forms with maladaptive personality traits, psychological distress, interpersonal functioning, and mental health treatment history, comparable to the full LPFS-SR.