Inventory of Problems–29 (IOP-29) and Inventory of Problems–Memory (IOP-M) failure rates in patients with severe psychosis with and without criminal convictions

Professionals are encouraged to include multiple symptom validity tests (SVTs) and multiple performance validity tests (PVTs) to assess the credibility of clinical and forensic presentations. Combining the Inventory of Problems-29 (IOP-29, an SVT) with its Memory module (IOP-M, a PVT), referred to here as 'IOP-29-M', may be especially beneficial, as it allows for rapid assessment of both symptom and performance validity. Accordingly, the present study aimed at 'stress testing' the IOP-29-M by examining base rates of failure (BRFail) in 109 patients with schizophrenia spectrum psychopathology, both with and without criminal convictions. In the overall sample, BRFail were low: 13.8% and 8.3%, respectively, for the standard (≥ .50) and conservative (≥ .65) cutoffs of the IOP-29, and 12.8% and 9.2%, respectively, for the standard (≤ 29) and conservative (≤ 28) cutoffs of the IOP-M. Importantly, very few individuals, less than 5%, failed both components of the IOP-29-M.