The Structured Inventory of Malingered Symptomatology Amnestic Disorders Scale (SIMS-AM) Is Insensitive to Cognitive Impairment While Accurately Identifying Invalid Cognitive Symptom Reporting

The amnestic disorders scale of the Structured Inventory of Malingered Symptomatology (SIMS-AM) assesses invalid memory symptom reporting. Although the SIMS manual recommends a highly sensitive cut-score of SIMS-AM > 2 for identifying symptom magnification, higher SIMS-AM cut-scores may reduce the risk of misclassification in clinical samples with potentially genuine cognitive impairment. The current investigation validated the SIMS-AM against performance validity tests (PVTs) and a well-established index of symptom invalidity—the response bias scale (RBS) from the Minnesota Multiphasic Personality Inventory-2-RF—in a mixed cognitive impairment sample. Using an actuarial approach for identifying cognitive impairment, ROC curves predicted performance and symptom invalidity indices while subdividing by cognitive impairment status. The SIMS-AM exhibited acceptable accuracy in classifying PVT status (AUC = .77), and a cut-score of SIMS-AM ≥ 9 yielded .90 specificity and .33 sensitivity. Classification accuracy remained acceptable regardless of cognitive impairment status (AUC ≥ .75), although a slightly higher cut-score of SIMS-AM ≥ 10 maintained a minimum specificity of .90 when differentiating cognitively impaired participants from participants with performance invalidity. Using the RBS as a criterion for invalid cognitive symptoms in the total sample, the SIMS-AM had excellent classification accuracy (AUC = .86), and a cut-score of SIMS-AM ≥ 9 maintained a minimum specificity of .90. Classification accuracy for detecting invalid cognitive symptom reporting remained excellent regardless of cognitive impairment status (AUC ≥ .85). Results demonstrate that the SIMS-AM is insensitive to cognitive impairment while accurately identifying performance and cognitive symptom invalidity within a mixed cognitive impairment sample.