Table 2.
Analyses of concordance of CSF Aβ42 and the Aβ42/40 ratio with amyloid PET status
| Parameter | Aβ42 | Aβ42/40 |
| Cut-off at the max. YI | 735 pg/mL | 0.05 |
| Sensitivity at the max. YI (95% CI) | 81.6% (68.0–91.2) | 95.9% (86.0–99.5) |
| Specificity at the max. YI (95% CI) | 72.7% (64.8–79.6) | 88.0% (81.7–92.7) |
| Positive PV (95% CI) | 49.4% (38.1–60.7) | 72.3% (59.8–82.7) |
| Negative PV (95% CI) | 92.4% (86.0–96.5) | 98.5% (94.7–99.8) |
| Accuracy (concordance proportion) | 74.9% | 89.4% * |
| % False Pos. (N)/% False Neg. (N) | 20.6% (41)/4.5% (9) | 9.0% (18)/1.5% (3) |
| Area Under the ROC curve (95% CI) | 0.814 (0.752–0.865) | 0.936† (0.892–0.966) |
*p < 0.001 compared to the Aβ42 concentrations (McNemar test for paired proportions); †p < 0.001 compared to the Aβ42 concentrations (DeLong test for differences in AUC’s); False positive, abnormal CSF/normal PET; false negative, normal CSF/abnormal PET; CSF, cerebrospinal fluid; PET, positron emission tomography; PV, predictive value; ROC, receiver operating characteristic; YI, Youden index.