First amyloid β1‐42 certified reference material for re‐calibrating commercial immunoassays

Introduction Reference materials based on human cerebrospinal fluid were certified for the mass concentration of amyloid beta (Aβ)1‐42 (Aβ42). They are intended to be used to calibrate diagnostic assays for Aβ42. Methods The three certified reference materials (CRMs), ERM‐DA480/IFCC, ERM‐DA481/IFCC and ERM‐DA482/IFCC, were prepared at three concentration levels and characterized using isotope dilution mass spectrometry methods. Roche, EUROIMMUN, and Fujirebio used the three CRMs to re‐calibrate their immunoassays. Results The certified Aβ42 mass concentrations in ERM‐DA480/IFCC, ERM‐DA481/IFCC, and ERM‐DA482/IFCC are 0.45, 0.72, and 1.22 μg/L, respectively, with expanded uncertainties (k = 2) of 0.07, 0.11, and 0.18 μg/L, respectively. Before re‐calibration, a good correlation (Pearson's r > 0.97), yet large biases, were observed between results from different commercial assays. After re‐calibration the between‐assay bias was reduced to