Table 4:

Accuracy of the cognitive charts for identifying participants with dementia in the validation sample population (National Alzheimer’s Coordinating Center’s Uniform Data Set (25))*

ParameterAt baseline
n = 7846
At 5-yr follow-up
n = 2230
At 9-yr follow-up
n = 510
Sensitivity (95% CI)65 (53 to 76)57 (29 to 82)64
Specificity (95% CI)98 (98 to 98)92 (91 to 93)92 (90 to 95)93
PPV (95% CI)17 (13 to 22)19 (8 to 33)10
NPV (95% CI)99 (99 to 99)99 (97 to 99)99
  • Note: CI = confidence interval, CSHA = Canadian Study of Health and Aging, (22) LR+ = positive likelihood ratio, LR− = negative likelihood ratio, NACC = National Alzheimer’s Coordinating Center’s Uniform Data Set, (25) NPV = negative predictive value, PPV = positive predictive value.

  • * In contrast with the results in Table 3 for the training sample population (CSHA), only healthy participants at the baseline measurement were included from the NACC’s UDS.

  • Consequently, we could only estimate specificity for the baseline measurement. In addition, the participants in the NACC’s UDS (25) were evaluated every year for a maximum of 10 yr; therefore, the results at 5- and 9-yr follow-up exclude participants with a diagnosis of dementia before those dates. We have not presented results at 10-yr follow-up to mirror the CSHA (22) study because attrition was too high by that time. However, the combined results take into account the full follow-up using the same procedure as in Table 3 and are comparable between the 2 data sets.

  • Combined values were obtained by modelling the relation between diagnoses and our classifier using repeated-measures logistic regression analyses. This takes into account the correlation between observations from a single participant; however, estimated sensitivities, specificities and predictive values are the same as if we had taken each individual observation independently. Consequently, we do not present confidence intervals for these combined values.