BACKGROUND. Few norms exist for the elderly on the cognitive tests
commonly used to screen for dementia; conventional cutpoints used in
clinical settings may be of limited value in population screening. A
particular problem is posed by elderly populations with low educational
levels, as performance on most cognitive tests is affected by education.
Thus, a healthy but poorly educated population may obtain test scores in
the range considered impaired in the clinical setting.
METHODS. A random
sample of 1,367 subjects aged 65+ years was screened for dementia in a
rural community in Southwestern Pennsylvania. Two sets of cognitive
measures were used: a global cognitive scale (the MMSE) and a brief
battery of tests tapping a variety of cognitive domains. Rather than using
a priori cutoff scores, we examined the specificity and sensitivity for
dementia of two operationally defined levels of cognitive impairment, at
the 5th and 10th percentiles of the study sample on each set of measures.
RESULTS. Results suggest that the screening of multiple cognitive domains
at the 10th percentile had significantly greater sensitivity but not lower
specificity for definite dementia than did the use of the single global
scale.
CONCLUSION. Our data support the use of population-based cutpoints
over standard cutoff scores, in that the global scale at the conventional
cutoff was less sensitive than the battery at the same percentile, and
because adequate norms do not exist for tests such as those in the
battery.