Table 3.
Ability of the odor identification score to discriminate between categories of the A/T/N classification and corresponding cut-off values.
| Analysis No | Group 1 | Versus Group 2 | Comparative pathological stage | Mean (SD) (Group 1/Group 2) | P-value (t-test) | AUC | 95% CI (De Long) | Cut-off | Specificity | Sensitivity |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | A−/T−/N− |
A+/T−/N− A+/T+/N− A+/T+/N+ |
Normal vs. after amyloidogenesis | 6.7(2.2)/4.5(2.1) | < 0.0001 | 0.761 | 0.658–0.864 | 5.5 | 0.676 | 0.659 |
| 2 |
A−/T−/N− A+/T−/N− |
A+/T+/N− A+/T+/N+ |
Normal to amyloidogenesis vs. after p-Tau accumulation | 6.3(2.3)/4.5(2.1) | 0.0006 | 0.717 | 0.604–0.83 | 4.5 | 0.830 | 0.514 |
| 3 |
A−/T−/N− A+T−/N− A+/T+/N− |
A+/T+/N+ | Normal to p-Tau accumulation vs. AD neurodegeneration | 6.1(2.2)/2.2(2.3) | 0.0011 | 0.716 | 0.588–0.844 | 4.5 | 0.786 | 0.545 |
| 4 | A−/T−/N− |
A−/T+/N− A−/T+/N+ |
Normal vs. p-Tau accumulation without amyloidogenesis | 6.7(2.2)/5.1(2.6) | 0.0049 | 0.670 | 0.546–0.794 | 4.5 | 0.892 | 0.486 |
| 5 | A−/T−/N− |
A−/T+/N− A−/T+/N+ A−/T−/N+ |
Normal vs. SNAP | 6.7(2.2)/5.2(2.5) | 0.0050 | 0.653 | 0.538–0.768 | 4.5 | 0.892 | 0.429 |
The discriminative ability of odor identification scores according to the A/T/N classification was evaluated. Regardless of the presence or absence of neurodegeneration, the AUC for odor identification scores was high when amyloidogenesis occurred (Analysis 1). Analyses 2 and 3 were less sensitive, making it difficult to differentiate the processes leading to p-Tau accumulation and neurodegenerative stages after amyloidogenesis. The AUC and sensitivity were low in the normal to p-Tau accumulation stage without amyloidogenesis regardless of the presence or absence of neurodegeneration (Analysis 4). After setting odor cut-off values for each A/T/N stage (A−/T−/N−, A+/T−/N−, A+/T+/N−, and A+/T+/N+), a post hoc power analysis was conducted; all stages met the criteria of a significance level of 5%, and a power of 80% at an AUC value ≥ 0.652. The results indicated that the sample size was sufficient to determine the cutoff value. Therefore, odor identification scores are excellent for differentiating amyloidogenesis but not p-Tau accumulation.
A (+) amyloid-positive individuals with A/T/N classification; A (−) amyloid-negative; T (+) p-Tau positive; T (−) p-Tau negative; N (+) t-Tau positive; N (−) t-Tau negative; SD standard deviation; AUC area under the curve; CI confidence interval; p-Tau phosphorylated Tau; SNAP suspected non-AD pathophysiology.