Automation on an Open-Access Platform of Alzheimer’s Disease Biomarker Immunoassays

Abstract

The lack of (inter-)laboratory standardization has hampered the application of universal cutoff values for Alzheimer's disease (AD) cerebrospinal fluid (CSF) biomarkers and their transfer to general clinical practice. The automation of the AD biomarker immunoassays is suggested to generate more robust results than using manual testing. Open-access platforms will facilitate the integration of automation for novel biomarkers, allowing the introduction of the protein profiling concept. A feasibility study was performed on an automated open-access platform of the commercial immunoassays for the 42-amino-acid isoform of amyloid-β (Aβ), Aβ, and total tau in CSF. Automated Aβ, Aβ, and tau immunoassays were performed within predefined acceptance criteria for bias and imprecision. Similar accuracy was obtained for ready-to-use calibrators as for reconstituted lyophilized kit calibrators. When compared with the addition of a standard curve in each test run, the use of a master calibrator curve, determined before and applied to each batch analysis as the standard curve, yielded an acceptable overall bias of -2.6% and -0.9% for Aβ and Aβ, respectively, with an imprecision profile of 6.2% and 8.4%, respectively. Our findings show that transfer of commercial manual immunoassays to fully automated open-access platforms is feasible, as it performs according to universal acceptance criteria.

Diagnostic and Prognostic Performance of Neurofilaments in ALS

“…Independent evaluation of the performance characteristics of the NF assays enables the public availability of data on the analytical quality of the different commercially available assays. Furthermore, automation of immunoassay facilitates single measurements with similar precision profiles as duplicate measurements in manually performed ELISAs, the former significantly reducing the implementation costs for patients (59). As the range of NF levels in ALS mimicking disorders is rather wide, the robustness of reported cut-offs might be challenged by the rather low number of ALS mimicking disorders included in most studies (23, 39).…”

Measurement batch differences and between‐batch conversion of Alzheimer's disease cerebrospinal fluid biomarker values

“…The fully automated platforms such as the Elecsys immunoassays are promising in controlling for batch variability, as evidence has shown for Abeta1-42, T-tau, and P-tau. [42][43][44] However, as novel CSF biomarkers are being developed, and it takes time for such platforms to become available for all biomarkers, statistical conversion models remain important for AD studies that include CSF data. Furthermore, the approaches for assessing and accounting for batch differences in the current study have the potential application for evaluating and adjusting for other sources of variability in measuring CSF biomarkers beyond batch difference, or studying other types of biomarkers such as imaging data.…”

“…However, such statistical harmonization does not lessen the importance of the aforementioned effort to minimize batch differences upfront. The fully automated platforms such as the Elecsys immunoassays are promising in controlling for batch variability, as evidence has shown for Abeta1‐42, T‐tau, and P‐tau 42–44 . However, as novel CSF biomarkers are being developed, and it takes time for such platforms to become available for all biomarkers, statistical conversion models remain important for AD studies that include CSF data.…”

Analytical performance of a CE-marked immunoassay to quantify phosphorylated neurofilament heavy chains

“…First, a standard calibration method where a distinct calibrator set was measured each analysis to construct a four parameter logistic (4-PL) calibration curve (GraphPad Prism 6, USA). Second, an experimental master calibration curve method where a 4-PL fixed calibration curve, obtained during the first analysis, was used to convert every optical density value generated in all analyses [3]. Leftovers of CSF, obtained via lumbar puncture for routine diagnostic purposes, were used.…”