Table 1.
Analytical assay characteristics
| Platform | ELISA colorimetric | SIMOA | ||||
|---|---|---|---|---|---|---|
| Analyte | Aβ1–42 | Aβ1–40 | t-tau | Aβ1–42 | Aβ1–40 | |
| Assay | Provider | EUROIMMUN | EUROIMMUN | ADx | ADx | ADx |
| Catalogue number | EQ 6521-9601 | EQ 6511-9601 | NA | NA | NA | |
| Biofluid | EDTA plasma | EDTA plasma | EDTA plasma | EDTA plasma | EDTA plasma | |
| Status | Commercial | Commercial | Prototype | Prototype | Prototype | |
| Specificity | Aβ1–42 | Aβ1–40 | 6 tau isoforms | Aβ1–42 | Aβ1–40 | |
| Dilution | Pre-dilution factora | 4 | 4 | 4 | 4 | 20 |
| Final sample dilutionb | 5 | 5 | 5 | 5.8 | 29 | |
| Calibrator | Type | Recombinant | Recombinant | Recombinant | Recombinant | Recombinant |
| No. of calibrator points | 7 | 7 | 7 | 7 | 7 | |
| Range, pg/mL | 1–40 | 1–75 | 1–100 | 1–64 | 1–64 | |
| Patient samples | Number | 199 | 199 | 199 | 199 | 199 |
| Range, pg/mL | 8.1–57.1 | 22.4–311.8 | 15.0–102.1 | 7.9–44.0 | 60.7–160.0 | |
| Within cal. range, % | 100% | 100% | 100% | 100% | 100% | |
| CV% | Intra-assay conc | 1.63 | 1.67 | 2.15 | 4.33 | 2.24 |
| Inter-assay conc | 4.82 | 2.58 | 13.55 | 8.59 | 5.95 | |
| Analytical sensitivity | LoD, pg/mL | 2.4 | 5.7 | Not determined | 0.46 | 0.77 |
| LoQ, pg/mL | 3.5 | 12.5 | Not determined | 1.21 | 1.57 | |
| S/N ratio | 7.60 | 65.4 | Not determined | 11.0 | 240 | |
| Antibodies [26, 27] | Name capture | ADx102 (21F12) | ADx103 (2G3) | ADx203 | ADx102 (21F12) | ADx103 (2G3) |
| Epitope capture (AA) | Aβ34–42 | Aβ33–40 | Tau194–204 | Aβ34–42 | Aβ33–40 | |
| Name detector | 2G3 | 2G3 | ADx204 | 2G3 | 2G3 | |
| Epitope detector (AA) | Aβ1–5 | Aβ1–5 | TauN-terminus | Aβ1–5 | Aβ1–5 | |
| Assay protocol | Incubation times, h | 3–0.5–0.5 | 3–0.5–0.5 | 3–0.5–0.5 | 2–0.08 | 2–0.08 |
| Incubation T, °C | 18–25 | 18–25 | 18–25 | 18–25 | 18–25 | |
| Curve fit | 4PL | 4PL | 4PL | 4PL | 4PL | |
| QC panel, pg/mL | QC1: high | 30.5 | 189.2 | 22.3 | 13.7 | 83.2 |
| QC2: intermediate | 26.6 | 149.1 | 18.9 | 19.7 | 75.9 | |
| QC3: intermediate | 22.0 | 116.8 | 21.7 | 13.4 | 69.7 | |
| QC4: low | 20.7 | 107.3 | 23.7 | 10.5 | 33.3 | |
| QC5: low spiked | 14.4 | 0.0 | NA | 21.6 | 21.8 | |
| QC6: high spiked | 117.9 | 125.6 | NA | 173.7 | 181.2 | |
| C1: low kit control | 23.3 | 114.6 | NA | NA | NA | |
| C2: high kit control | 45.1 | 186.9 | NA | NA | NA | |
AA amino acid, Aβ β-amyloid, CV coefficient of variation, LoD limit of detection, LoQ limit of quantification, S/N ratio signal to noise ratio, QC quality control, T temperature, t-tau total tau
aSample pre-dilution was performed using assay diluent in polypropylene low-binding 96-well microplates
bFinal sample dilution during sample incubation step in assay protocol