There were statistically significant age effects among groups [F(2,125) =4.40; p<.02]. Level of educational attainment did not significantly differ among the groups [F(2,125)=1.20; p>.30]. A Scheffe’ test of means indicated that cognitively normal elderly subjects tended to be younger than pAD groups. There was also a greater percentage of females in the cognitively normal group [Χ2 (df=2) = 9.54; p<.009] and a greater number of English-speakers [Χ2 (df=2)= 7.07; p<.03]. Groups differed on their MMSE scores [F(2,124)=72.63; p<.001]. The highest MMSE scores were obtained by cognitively normal subjects, followed by MCI subjects, with the lowest scores obtained by the pAD group.
Despite some initial demographic differences among study groups, neither age (r=−.08; df=78, p= .49) nor level of educational attainment (r= −.08; df=78, p= .47) were associated with FBMS performance among cognitively normal subjects. In addition, there was no association between gender (r=.18; df=78, p= .11) or language (r=−.04; df=78, p= .71) on level of performance on the FBMS. Among cognitively impaired (i.e., pAD and aMCI) subjects, age (r =−.09; df=46; p=.55), gender (r =−.24; df=46; p=.11) and language (r =−.15; df=46; p=.31) were not associated with level of performance on the FBMS. Although there was a weak correlation between level of educational attainment and FMBS (r=.297; df=46, p=.04), education explained less than 9% of the total variability in FMBS scores.
Test-Retest Reliabilities And Concurrent Validity
The test-retest reliability for the FBMS among a subset of 29 cognitively impaired subjects who had either been diagnosed with pAD or aMCI over an average 9 week test-retest interval was r=.65 (p<.001). Among sixty of the 128 subjects in the total sample who had neuropsychological test scores, there was a high level of association of the FBMS with immediate memory for passages (r=.80; p<.001); the delayed memory for passages (r=.79; p<.001), the free recall of the Fuld Object Memory Evaluation (r=.73; p<.001) and Bag B Recall of the Semantic Interference Test (r=.70; p<.001). Among 19 cognitively impaired subjects with pAD or aMCI, the association of the FBMS with the MMSE was r=.75 (p<.001), with the immediate memory for passages was r=.53 (p<.03), with the delayed memory for passages was r=.44 (p<.06), with the free recall of the Fuld Object Memory Evaluation was r=.54 (p<.02), and with Bag B Recall of the Semantic Interference Test was r=.66; (p<.003).
The scores of the patients in the MCI and pAD groups were compared to those of the cognitively normal group. ROC analyses using SPSS 15 indicated that for aMCIpAD/normal contrasts the area under the curve (AUC) was .895 (SE=.04; 95% CI of .819 to .970) which was statistically significant at p<.001 (Wilcoxon z = 22.4). For PAD normal comparisons, the AUC was .975 (SE=.01; 95% CI of .950 to .999) which was statistically at p<.001 (Wilcoxon z = 97.5). As indicated in , an optimal cut-off of 7 resulted in correct classification of 82.6% of aMCI patients and 100% of pAD patients while correctly classifying 87.5% of cognitively normal subjects.
Sensitivity and Specificity of Cut-Off Scores for Amnestic MCI and Probable AD Subjects Versus 80 Cognitively Normal Elders