Classification accuracy of the symptom validity tests Word Memory Test and the German version of the Structured Inventory of Malingered Symptomatology

Abstract

The symptom validity tests Word Memory Test (WMT) and "Strukturierter Fragebogen Simulierter Symptome" (SFSS, German version of the Structured Inventory of Malingered Symptomatology, SIMS) are used in psychiatric expert reviews in the context of social benefit proceedings to elucidate the validity of apatient's symptom presentation and to unveil possible malingering. Many of the studies on the WMT and the SFSS estimated the sensitivity and specificity of the tests by using student populations or healthy volunteers. The objective of the present study was to investigate the accuracy of the WMT and the SFSS in aclinical sample and if their combined use leads to better classification results. The study was conducted as arandomized controlled trial (RCT) with 60 inpatients and outpatients with depressive and anxiety disorders. The patients randomly received one of two different instructions. The control group was instructed to answer honestly. The intervention group received the instruction to imagine themselves in the situation of asocial benefit claimant who wants to emphasize a medical condition. For the WMT and its recommended cut-off of ≤82.5% the sensitivity was determined to be 80% and the specificity 93.3%. The SFSS achieved asensitivity of 93.3% and aspecificity of 70% with the recommended cut-off of >16. The combined deployment of the tests attained asensitivity of 92.3% and aspecificity of 95.2%. Only the combined deployment of the WMT and the SFSS yielded satisfactory results. Given the high probability of false positive classifications of malingering, the use of one of the tests alone cannot be recommended.