Assessment, Ahead of Print.
As previous studies have shown that personality disorder (PD) assessment in older adults is often hampered because assessment tools are tailored toward younger adults, establishing the age-neutrality of novel tools is crucial. This study primarily aimed to evaluate the age-neutrality of the Level of Personality Functioning Brief Form (LPFS-BF 2.0) and the Personality Inventory for DSM-5 Modified + (PID-5-BF+M), using a sample of 254 community-dwelling adults. The analysis of Differential Item Functioning (DIF) demonstrated the age-neutrality of both instruments, with only 8.3% of LPFS-BF 2.0 items and 5.6% of PID-5-BF+M items exhibiting DIF. Differential Test Functioning (DTF) analyses revealed large DTF for the LPFS-BF 2.0 total score, indicating that age-specific norms might be necessary for this score. In summary, this study supports the use of these instruments in both older and younger adults, enhancing the assessment of PDs across the life span.