High specificity of the Word Memory Test and Medical Symptom Validity Test in groups with severe verbal memory impairment.

By definition, false positives occur when an otherwise very easy symptom validity test (SVT) or effort test is failed because of cognitive impairment and not because of poor effort. Therefore, the highest rate of false positives will be found in those groups with the most severe cognitive impairment. For that reason, it is important to study people with severe impairment when evaluating the specificity of SVTs. Some people with various types of dementia, notably those with Alzheimer's disease, suffer from severe impairment of memory and other cognitive abilities. In this study, patients with possible or probable dementia were tested with the Word Memory Test (WMT; Green, 2003; Green & Astner, 1995) and the Medical Symptom Validity Test (MSVT; Green, 2004). While some dementia patients failed the easy subtests of these instruments and had severe verbal memory impairment, they showed distinctive profiles of scores that have been reported to be characteristic of people with severe impairment. Using profile analysis, the WMT and MSVT achieved a specificity of 98.4% or higher in the patients of the current study. This suggests that there will be extremely low false positive rates using the same methods in people with relatively minor impairment of the type found in, for example, mild traumatic brain injury or depression.