Aim: Research shows that characteristics of personality disorders (PDs) can differ with age (Penders et al., 2020). As a result, age-neutral personality tests are crucial for obtaining an accurate assessment of PDs in older adults. The current categorical PD criteria lack this age-neutrality, causing misestimation of personality pathology in this age-group. To fill in this knowledge gap, this study examined the age-neutrality of the Personality Inventory for DSM-5 Brief Form + Modified (PID-5-BF +M) and the Level of Personality Functioning Scale 2.0 (LPFS-BF 2.0). These instruments operationalize the ICD-11 and DSM-5 dimensional classification of PDs, that might hold more promise for older adults.
Method: Age-neutrality was evaluated in nonclinical samples of 129 younger (18-64) and 129 older (65-92) adults, by means of Differential Item Functioning (DIF). If an item shows DIF, younger and older adults with a similar position on the underlying construct do not have the same probability of endorsing that item. An instrument is considered not age-neutral, when more than 25% of its items display DIF. The impact of DIF at scale-level can be examined by Differential Test Functioning (DTF).
Results: In both instruments, less than 25% of the items displayed DIF. However, when examining the impact of DIF at scale-level through DTF, the PID-5-BF+M-scales Detachment and Antagonism and the LPFS-BF 2.0-scale Interpersonal-functioning showed large DIF.
Conclusion: The results corroborated the age-neutrality of both measures as a whole. However, further improvement of non-age-neutral items and/or developing age-appropriate norms for the scales showing large DIF is necessary in order to obtain instruments that result in accurate assessment both in younger and older adults.