<i>Take</i> Their Word for It: The Inventory of Problems Provides Valuable Information on Both Symptom and Performance Validity
Matthew Holcomb, Sadie R. Pyne, Laura Cutler, David A. Oikle, László A. Erdődi
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.