Disabilità cognitiva e diagnosi di simulazione: una prova di riconoscimento di numeri a scelta obbligata

Objective: to investigate the usefulness of a Forced Choice Recognition Memory Test for Numbers to detect malingering or exaggeration of cognitive dysfunctions in order to obtain compensation. Subjects: Malingering was assessed in 2 normal groups, both of 50, and 3 pathological groups: mild traumatic brain injured subjects (n 30), minimal (n 20) and mild Alzheimer subjects (n 20), and mental retarded subjects (n 20). Test and Procedures: The forced choice recognition memory test for numbers requires subjects to identify wich of two five digit numbers shown on a card was the same as a number seen prior to a brief delay. Two sets of 18 trials have delays of 5 and 10 sec, for a total of 36 trials. Results: In normal group, who was asked to answer at random, correct choices were the 47%, while in the second normal group, using standard procedure, were at maximum level. Alzheimer patients, specially minimals, performed like normals. Mental retarded showed only mild impairment. Both pathological groups averaged over 90% correct responses, in contrast to a group of suspected malingerers TBI whose correct responses averaged only 25%. Moreover, TBI showed an inconsistency between initial injury severity and level of neuropsychological test performance. Conclusions: The findings suggest that financial incentives and inconsistency in performance levels are important risk factors with regard to invalid performance during neuropsychological evaluations of traumatic brain injury subjects. The Forced Choice Recognition Memory Test for Numbers appears to offer a good support to detect this possible influence. This Test is a very short and quick procedure that doesn’t require any complex attentive, perceptive and mnesic processes. Even a few errors should raise the suspicion of poor motivation on a test this easy. In fact, administering this task to groups of mild Alzheimer and mental retarded subjects found that both patients groups made almost perfect score. When a disability would be advantageous, complaints that appear to exceed by far what the injury would be expected to cause signal the possibility of malingering. This test is easier and quickler than the others clinical tests currently available and results effective in classifying patients and simulators correctly. So, it can be used in neuropsychological assessment, specially in insurance and litigation context. However, malingering detection need a thorough neuropsychological examination in conjunction with careful clinical studies and case-history investigation. Only this holistic approach will bring out performance discrepancies that are inconsistent with normal neuropsychological expectations and simultaneously it will avoid underestimation of real cognitive dysfunctions.