Comparison of two analytical platforms for the clinical qualification of Alzheimer's disease biomarkers in pathologically-confirmed dementia.

Combined analysis of the Alzheimer's disease (AD) biomarkers amyloid-β(1-42) (Aβ(1-42)), total tau (T-tau), and hyperphosphorylated tau (P-tau(181P)) in cerebrospinal fluid (CSF) reduces the uncertainty associated with clinical dementia diagnosis. The present study evaluated the diagnostic accuracy of the CSF biomarker concentrations obtained with a multi-analyte Luminex assay (INNO-BIA AlzBio3) in comparison to single-analyte ELISA tests (INNOTEST). Data from 66 pathologically-confirmed dementia patients (51 AD and 15 non-AD) and 95 controls were included. Cut-off values were determined for each individual biomarker determined using both methods for different diagnostic challenges (dementia-controls; AD-controls; AD-non-AD). Comparing the diagnostic accuracy of individual cut-off values between INNO-BIA and INNOTEST, no relevant differences could be identified. Logistic regression was used in addition to identify the best combination of predictor variables (biomarkers). Discrimination of dementia patients from controls using Aβ(1-42) and T-tau yielded a diagnostic accuracy of 0.87 and 0.90 for INNO-BIA and INNOTEST, respectively. Discriminating AD patients from controls, the diagnostic accuracy was 0.90 and 0.93 for INNO-BIA and INNOTEST, respectively. Optimal discrimination of AD and non-AD patients was achieved by combining Aβ(1-42) and P-tau(181P) (diagnostic accuracy = 0.86). In conclusion, which AD biomarkers or combination thereof are most informative is dependent on the differential diagnosis, but the clinical value of these markers in each of the differential diagnoses is independent of the method by which concentrations are determined. Since the clinical value of the ELISA (INNOTEST) and Luminex (INNO-BIA) tests is comparable, further research to select the most suitable analytical platform for routine CSF biomarker measurements is needed.