Stability performance of a fully automated, chemiluminescent, beta-amyloid 42 assay

Beta amyloid 1–42 (Aβ42) concentration in CSF has been shown to correlate with Alzheimer's disease (AD) progression and is a key measurement in the assessment of AD risk and status. The use of such markers for clinical purposes requires assays that can deliver consistent analytical and clinical performance. We report on the VITROS ® Immunodiagnostic Products Amyloid Beta 42 Assay (AB-42)1 under development for the measurement of Aβ42 in CSF on the VITROS Immunodiagnostic Systems. The objective of this study was to demonstrate the stability of the assay reagents over a 54 week period. One lot of VITROS AB-42 assay reagent was stored at 2–8°C and tested on the VITROS ® ECiQ Immunodiagnostic System at 13 timepoints over a 54 week period to demonstrate the stability of the reagents. Five controls ranging in concentration from50 pg/mL to 1200 pg/mL were run in duplicate at each timepoint. In the first part of the study the reagents were calibrated off Reference Calibrators every 28 days over a 16 week period to demonstrate calibration stability. In the second part of the study the reagents were calibrated at each timepoint over a 54 week period. In each study the percent change in predicted concentration at each timepoint was calculated along with the mean and range in percent change. The %CV was also calculated across all timepoints in each study. For the 16 week study, the mean percent difference from time zero ranged from -1.3% to 0.9% across all controls. The percent difference from time zero at each timepoint ranged from -5.5% to 3.2%. The %CV across all timepoints for each control ranged from 1.1% to 1.9%. For the 54 week study, the mean percent difference from time zero ranged from 0.3% to 2.3% across all controls. The percent difference from time zero at each timepoint ranged from -1.3% to 4.5%. The %CV across all timepoints for each control ranged from 1.0% to 1.5%. The VITROS Immunodiagnostic Products Amyloid Beta 42 Assay 1 has demonstrated consistent results with reagents stored at 2–8°C over more than a year.