Sensitivity and specificity of some neuropsychological markers of Alzheimer dementia

A standardized neuropsychological test battery was administered to 167 pati ents with different forms of mild-to-moderate dementia: probable Alzheimer dementia (AD: n = 49), multi-infarct dementia (n = 43), idiopathic Parkinso n disease with dementia (n = 35), depressive pseudodementia (n = 26), and p rogressive supranuclear palsy (n = 14). Results obtained were used (a) to a nalyze the profiles of cognitive impairment shown by the different dementia groups; (b) to assess the incidence of some neuropsychological patterns th at we hypothesized to be more characteristic of AD, in the various groups; and hence (c) to evaluate the reliability of these patterns as diagnostic m arkers of AD. Four of the patterns investigated were derived from a verbal learning task (Rey's Auditory Verbal Learning test): (1) absence of the pri macy effect; (2) tendency to produce intrusion errors during fi-ee recall o f a word list; (3) absolute decay of memory trace; and (4) tendency to prod uce false alarms during delayed recognition of the same word list. Two addi tional patterns were derived from visual-spatial tasks (copying drawings an d Raven's Coloured Progressive Matrices): (5) occurrence of the closing-in phenomenon in copying drawings; and (6) tendency to choose globalistic or o dd responses in Raven's matrices. Though all the six patterns were somewhat useful for identifying AD patients, no pattern met the criteria of being b oth highly sensitive and highly specific, which should characterize an idea l marker. In fact, intrusions and false alarms were observed in many AD pat ients, but also in patients affected by other forms of dementia. The absenc e of the primacy effect, the closing-in phenomenon, and the absolute decay of memory trace were more specific, but could be observed in only one-third of AD patients. We also computed the number of positive patterns shown by each patient and assumed the presence of two or more patterns as a global i ndex suggestive of a dementia of the Alzheimer type. With this cumulative m ethod, a higher level of sensitivity and specificity was achieved in the id entification of AD patients.