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))*
| Parameter | At baseline n = 7846 | At 5-yr follow-up n = 2230 | At 9-yr follow-up n = 510 | Combined† |
|---|---|---|---|---|
| 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 |
| LR+ | – | 8.1 | 7.1 | 9.14 |
| LR− | – | 0.38 | 0.47 | 0.39 |
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.