Qualitative features of the neuropsychological
test performance of individuals with dementia of the Alzheimer
type (DAT) were examined in a population-based study. Qualitative
error scores were derived from measures of verbal and figural
memory, verbal fluency and confrontation naming for 38
patients with clinically diagnosed DAT, 236 normal elderly
(NE) individuals, and 72 others who were questionably demented
and at risk (AR) for DAT. Persons with DAT made
a greater proportion of intrusion and perseverative errors,
and more lexical and semantic naming errors, than the NE
participants. These measures provided fair specificity
but poor sensitivity for the diagnosis of DAT, and a logistic
model based on these measures correctly classified 98%
of the NE participants, but only 29% of the DAT participants.
The AR participants demonstrated a pattern of errors that
was highly similar to that of the DAT patients, and when
their scores were subjected to the logistic model, 90%
were classified as NE and 10% as DAT. These results indicate
that specific error types that have been associated with
DAT in self-referred or clinic-based samples also occur
in the general population to a greater degree in individuals
with DAT or questionable dementia than in NE individuals.
Furthermore, these qualitative features may have some diagnostic
usefulness in that their presence provides reasonable specificity
for DAT or questionable dementia. (JINS, 1997,
3, 387–393.)