The Cross-Cultural Applicability of the Inventory of Problems – 29 (IOP-29): A Replication of Akca et al. (2023) Using a Serbian Sample

Some widely agreed-upon, official recommendations for professionals conducting psychological assessments suggest employing multiple symptom validity tests (SVTs) to screen the validity of symptom reports. Yet, SVTs are rarely validated in languages other than English, and no free-standing SVT exists in Serbia. To address this gap and stimulate further research on symptom validity within populations from the Balkans, we developed and tested a Serbian version of the Inventory of Problems – 29 (IOP-29). Following the same procedures used in prior IOP-29 validation studies (e.g., Akca et al., 2023), we administered the Serbian IOP-29 to 110 adult volunteers from Serbia. Participants completed the IOP-29 three times under different conditions: responding honestly, randomly, or by feigning a mental disorder (schizophrenia, depression, or post-traumatic stress disorder). We examined the utility of both the False Disorder Probability Score (FDS), which is the chief feigning index of the IOP-29, and of a new index embedded in the IOP-29, which is aimed at detecting random or careless responding. Overall, our results demonstrated that the FDS effectively differentiated between feigned and honest presentations, achieving a sensitivity of 0.86 and a specificity of 0.96 when using the standard cutoff (FDS ≥ 0.50). In addition, the random responding index also successfully identified random responding, achieving a sensitivity of 0.64 and a specificity greater than 0.90 when using a midrange cutoff of T ≥ 67. These findings closely align with outcomes of Akca et al. (2023) and support meta-analytic literature reviews on the IOP-29. More broadly, this study advances and encourages further exploration of symptom validity testing in culturally diverse populations.