Psychometric tests for malingering in persons with a diagnosis of depression
Objective. To determine psychometric test cut scores for malingering in a sample of depressed patients. Design. A prospective study of depressed persons randomly assigned either to a comparator group that was instructed to feign illness or to a control group instructed to perform optimally on a set of psychometric tests. Setting. The study was conducted at the Department of Psychiatry and the Clinical Psychology Section of the Centre for Student Counselling and Development, both of the University of Stellenbosch. Subjects. Fifty-one patients with depression. Outcome measures. Each subject completed the Dot-Counting Test (DCT), the Rey 15-item Test (Rey 15-item), the 21-item verbal memory Forced Choice Test (FCT), the Word Recognition (WR) test and the Structured Inventory of Malingered Symptomatology (SIMS). Results. The psychometric tests correctly distinguished between simulation and optimal performance in 61 - 75% of subjects. Sensitivity ranged from 54% to 92% and specificity between 36% and 96%. The FCT, WR test and SIMS total score gave the best results for individual tests. A discriminant function that combined FCT, DCT and SIMS total score optimised sensitivity (69%) and specificity (92%). Conclusions. The presence of depression complicates interpretation of psychometric tests for malingering. A combination of screening measures for malingering provides superior results compared with individual tests. The results of this study should help with the generalisation of psychometric tests for malingering to clinical populations.