Take Their Word for It: The Inventory of Problems Provides Valuable Information on Both Symptom and Performance Validity.

ABSTRACT

This study was designed to compare the validity of the Inventory of Problems (IOP-29) and its newly developed memory module (IOP-M) in 150 patients clinically referred for neuropsychological assessment. Criterion groups were psychometrically derived based on established performance and symptom validity tests (PVTs and SVTs). The criterion-related validity of the IOP-29 was compared to that of the Negative Impression Management scale of the Personality Assessment Inventory (NIMPAI) and the criterion-related validity of the IOP-M was compared to that of Trial-1 on the Test of Memory Malingering (TOMM-1). The IOP-29 correlated significantly more strongly (z = 2.50, p = .01) with criterion PVTs than the NIMPAI (rIOP-29 = .34; rNIM-PAI = .06), generating similar overall correct classification values (OCCIOP-29 79-81%; OCCNIM-PAI 71-79%). Similarly, the IOP-M correlated significantly more strongly (z = 2.26, p = .02) with criterion PVTs than the TOMM-1 (rIOP-M = .79; rTOMM-1 = .59), generating similar overall correct classification values (OCCIOP-M 89-91%; OCCTOMM-1 84-86%). Findings converge with the cumulative evidence that the IOP-29 and IOP-M are valuable additions to comprehensive neuropsychological batteries. Results also confirm that symptom and performance validity are distinct clinical constructs, and domain specificity should be considered while calibrating instruments.