Pseudodiagnoses of Malingering of Neuropsychological Symptoms in Survivors of Car Accidents by the Structured Inventory of Malingered Symptomatology

Background: The Structured Inventory of Malingered Symptomatology (SIMS) is a widely used test allegedly designed for detection of malingering medical symptomatology. Even a brief perusal of its 75 True-False items reveals that too many of these list legitimate medical symptoms, in particular, symptoms within the post-concussion-whiplash spectrum, as experienced by survivors of motor vehicle accidents (MVAs). The present study examined conceptual overlap of SIMS items with symptoms assessed by the Rivermead Post-Concussion Symptoms Questionnaire and also with symptoms assessed by the scale of Post-MVA Neurological Symptoms (PMNS).

Materials and Method: De-identified archival data of 98 patients (mean age 42.2 years, SD=14.3, 38 males, 60 females) containing scores on Rivermead and PMNS were tabulated to list frequencies of each endorsed symptom. Next to these symptoms, SIMS items were tabulated which conceptually overlap with legitimate post-concussive or post-whiplash neuropsychological signs listed in Rivermead and PMNS.

Results: More than a half of the 75 SIMS items could be potentially endorsed by post-MVA patients due to their neuropsychological symptoms, without any intent to malinger. Each of the SIMS items counts one point towards a cutoff point of > 14: thus, the majority of post-MVA patients are likely to be misclassified by SIMS as malingerers. Many of the other remaining SIMS items could be endorsed by non-malingering patients with some other medical conditions such as acute schizophrenia, or low intelligence, etc. Almost no SIMS items appear suited to reliably differentiate malingerers from legitimate medical patients.

Discussion and Conclusions: A thorough review of all 75 SIMS items suggests that most of them would not adequately differentiate non-malingering persons from malingerers: the items were included in the SIMS without their author’s sufficient knowledge of the wide range of possible psychopathology and of other medical conditions. This is consistent with the lack of satisfactorily designed validation studies of the SIMS that would meet standards of the American Psychological Association for tests meant to perform diagnostic tasks. The rates of false positive with SIMS are unacceptably high: clinical use of SIMS implies malpractice.

Keywords: Post-Concussion syndrome, Whiplash, Neurologic Impairment, Malingering, False Positives.