Background: The purpose of this study was to evaluate the utility (i.e., po
sitive and negative predictive value) of the 7 Minute Screen in identifying
patients with probable Alzheimer's disease (AD) in a primary care practice
. A second objective was to estimate the number of undiagnosed AD patients
in a typical primary care practice. Methods: One hundred thirty-seven succe
ssive admissions (96%) of patients over the age of 60 to a primary care pra
ctice over a 53-day period who completed informed consent documents were ad
ministered the 7 Minute Screen. All patients who screened positive (n = 13)
and a random sample of those who screened negative (n = 26) returned for f
ull diagnostic evaluation. Positive predictive value (PPV) and negative pre
dictive value (NPV) of the 7 Minute Screen were determined using the criter
ion standard of clinical diagnosis established by examination, history, and
laboratory studies. Test-retest reliability and time for administration we
re also determined. Results: Of the 137 patients evaluated, 13 screened pos
itive and 124 screened negative. Eleven of the 13 patients who screened pos
itive were willing to return to the primary care practice for follow-up eva
luation. A random sample of 26 patients who screened negative all agreed to
return for follow-up evaluation. Of the 11 patients who screened positive
and who returned for evaluation, 10 were subsequently diagnosed with probab
le AD. The remaining patient was diagnosed with mixed dementia. The caregiv
ers of the two patients who refused to return were contacted and both indic
ated that the patients were having significant cognitive problems as verifi
ed by an activities of daily living scale. Of the 26 patients who screened
negative, 25 were judged to be cognitively normal and the 26th was judged t
o have mild cognitive impairment. Discussion: In successive admissions of p
atients over the age of 60 in a primary care practice, the 7 Minute Screen
showed a PPV of 91% and an NPV of 96% in identifying patients who were subs
equently identified with AD or other dementing disorder. These data suggest
that this may be a useful instrument in identifying patients who should un
dergo diagnostic evaluation for AD and other dementing disorders. Additiona
lly, extrapolation from the data in this practice suggests that there may b
e between 75 and 100 AD patients in the typical primary care practice, many
of whom may not be diagnosed.