Is theMWT-A Suitable for the Estimation of Premorbid Intelligence Level? Testing on a Consecutive Sample froma Specialized Outpatient Clinic for Dementia

Vocabulary tests have long been used for estimating premorbid intelligence level in the neuropsychological assessment of dementia. However, doubts exist about the validity of such intelligence tests. The present study examines whether the Multiple-Choice Vocabulary Test - Version A (Mehrfachwahl-Wortschatz-Test - Version A, MWT-A) is valid for assessing premorbid intelligence level. Data from a total of 821 patients in a specialized outpatient clinic for dementia (memory clinic), covering the whole spectrum of cognitive impairment, were evaluated using analysis of variance with the dependent variable premorbid intelligence level (MWT-A) and the independent variable extent of global cognitive impairment (Mini-Mental-State Examination, MMSE: mean = 25.2, SD = 3.9). The latter was divided into six MMSE ranges or groups, respectively (29-30, 28-28, 27-27, 25-26, 22-24, 05-21). In the case of a pathologically relevant global cognitive impairment (24-26 MMSE points), the MWT-A underestimates the premorbid intelligence level. This effect is moderated neither by age nor education. Results indicate that the MWT-A is unsuitable for estimating premorbid intelligence level in neuropsychological assessments of cognitively impaired patients or demented patients.