The Inventory of Problems–29 is a Cross-Culturally Valid Symptom Validity Test: Initial Validation in a Turkish Community Sample

Abstract Because the actuarial evidence base for symptom validity tests (SVTs) is developed in a specific population, it is unclear whether their clinical utility is transferable to a population with different demographic characteristics. To address this, we report here the validation study of a recently developed free-standing SVT, the Inventory of Problems-29 (IOP-29), in a Turkish community sample. We employed a mixed design with a simulation paradigm: The Turkish IOP–29 was presented to the same participants ( N = 125; 53.6% female; age range: 19–53) three times in an online format, with instructions to respond honestly (HON), randomly (RND), and attempt to feign a psychiatric disorder (SIM) based on different vignettes. In the SIM condition, participants were presented with one of three scripts instructing them to feign either schizophrenia (SIM-SCZ), depression (SIM-DEP), or posttraumatic stress disorder (SIM-PTSD). As predicted, the Turkish IOP–29 is effective in discriminating between credible and noncredible presentations and equally sensitive to feigning of different psychiatric disorders: The standard cutoff (FDS ≥ .50) is uniformly sensitive (90.2% to 92.9%) and yields a specificity of 88%. Random responding produces FDS scores more similar to those of noncredible presentations, and the random responding score (RRS) has incremental validity in distinguishing random responding from feigned and honest responding. Our findings reveal that the classification accuracy of the IOP–29 is stable across administration languages, feigned clinical constructs, and geographic regions. Validation of the Turkish IOP–29 will be a valuable addition to the limited availability of SVTs in Turkish. We discuss limitations and future directions.