Table 2. Random Forest models.
| (A) Description of variables included in the models | ||
|---|---|---|
| Model 1 | Model 2 | Model 3 |
| Demographic-clinical variables | Memory variables | Non-memory cognitive variables |
| Age | AVLT Learning trial 1 | WAIS-R Digit Symbol |
| Gender | AVLT Learning trial 2 | WMS-R Digit forward span |
| Years of education | AVLT Learning trial 3 | WMS-R Digit forward length |
| APOE status | AVLT Learning trial 4 | WMS-R Digit backward span |
| GDS | AVLT Learning trial 5 | WMS-R Digit backward length |
| FAQ | AVLT Learning trial 1 errors | TMT-A correct answers |
| CDR | AVLT Learning trial 2 errors | TMT-A commission errors |
| MMSE | AVLT Learning trial 3 errors | TMT-A omission errors |
| CSF Aß42a | AVLT Learning trial 4 errors | TMT-B correct answers |
| CSF Total taua | AVLT Learning trial 5 errors | TMT-B commission errors |
| CSF p-taua | AVLT B (interference) | TMT-B omission errors |
| Disease durationa | AVLT B (interference) errors | Verbal Fluency – vegetables |
| Age of onseta | AVLT immediate free recall | Verbal Fluency – vegetables intrusions |
| AVLT immediate free recall errors | Verbal Fluency – vegetables perseverations | |
| AVLT delayed free recall | Verbal Fluency – animals | |
| AVLT delayed free recall errors | Verbal Fluency – animals intrusions | |
| AVLT recognition | Verbal Fluency – animals perseverations | |
| AVLT recognition errors | BNT total | |
| BNT spontaneous | ||
| BNT number semantic cues | ||
| BNT spontaneous + semantic | ||
| BNT number phonetic cues | ||
| BNT spontaneous + semantic + phonetic | ||
| Clock Test drawing | ||
| Clock Test copy | ||
| (B) Summary of results | ||
| Model 1 | Model 2 | Model 3 |
| N = 415 | N = 408 | N = 398 |
| Error by chance = 80% | Error by chance = 80% | Error by chance = 80% |
| Classification error: | Classification error: | Classification error: |
| Healthy controls: 0% | Healthy controls: 4% | Healthy controls: 3% |
| Typical AD: 16% | Typical AD: 23% | Typical AD: 25% |
| Limbic-predominant: 88% | Limbic-predominant: 100% | Limbic-predominant: 100% |
| Hippocampal-sparing: 82% | Hippocampal-sparing: 100% | Hippocampal-sparing: 97% |
| No atrophy group: 63% | No atrophy group: 100% | No atrophy group: 100% |
aThe same model was repeated including CSF biomarkers in all the sample (model 1’), and CSF biomarkers + disease duration + age of onset only in Alzheimer’s disease patients (model 1”). Results obtained were the same as in model 1. Results presented in the manuscript Fig. 3 are those from model 1 (8 variables). APOE = apolipoprotein E; GDS = geriatric depression scale; FAQ = functional activities questionnaire; CDR = clinical dementia rating; MMSE = mini-mental state examination; CSF = cerebrospinal fluid; Aß1-42 = amyloid-ß-peptide 1–42; T-tau = total level of tau protein; AVLT = Auditory Verbal Learning test; WAIS-R = Wechsler Adult Intelligence Scale – Revised; WMS-R = Wechsler Memory Scale – Revised; TMT-B = Trail Making Test part B; BNT = Boston Naming Test; AD = Alzheimer’s disease.