High Risk of False Classification of Injured People as Malingerers by the Structured Inventory of Malingered Symptomatology (SIMS): A Review

Background: Tests that purport to measure malingering such as the Structured Inventory of Malingered Symptomatology (SIMS) are associated with a risk to the public. The magnitude of this risk can be operationalized as the frequency of false positives, i.e., proportion of persons classified as malingerers and thus denied therapy and other medical benefits.

Method: This review deals with the outcomes of studies of content, divergent, and criterion validity of the SIMS. We calculated an average risk to the public caused by the rates of false positives in published SIMS data on several clinical groups: psychiatric patients, survivors of high impact motor vehicle accidents (MVAs), and trauma-exposed war veterans.

Results: (1) Content analyses demonstrated that almost all SIMS items describe medical symptoms, but these are fallaciously scored by the SIMS as indicative of malingering.

(2) Calculations of divergent validity suggest that the SIMS measures the presence of medical symptoms rather than their malingering. For instance, SIMS total score correlates positively and highly with PCL-5 measure of PTSD (r=.60). The SIMS Amnestic Disorder scale correlates positively with Rivermead measure of post-concussive symptoms (r=.42). The SIMS Neurological Impairment scale correlates positively with neuropsychological symptoms measured by Post-MVA Neurological Symptoms (PMNS) scale (r=.41).

(3) Criterion validity results of a recent meta-analysis indicated no significant capacity of the SIMS to differentiate legitimate patients from malingerers. Furthermore, published SIMS data indicate extremely high rates of false positives: 82.7% of US veterans with PTSD, 78.3% of patients injured in high impact MVAs, and 72.0% of legitimate psychiatric inpatients. An average risk to the public (i.e., the risk for genuine medical patients to be falsely classified as malingering) as suggested by the weighted mean for these SIMS data is 78.8%. Patients with more medical symptoms are significantly more likely to be fallaciously classified by their SIMS scores as “malingerers” than their less symptomatic counterparts.

Discussion and Conclusions: The SIMS is a fatally flawed psychological test with alarmingly high iatrogenic rates. Its use constitutes malpractice.

Keywords: malingering, risk to public, SIMS, neuropsychology, neurology.