Fig. 3
Correlations and commutability between ELISA and SIMOA measurements of β-amyloid (Aβ) isoforms Aβ1–40 and Aβ1–42. a, b Box and whisker plots of ELISA (left, blue) and SIMOA (right, orange) measurements of plasma Aβ1–40 (a) and Aβ1–42 (b) are shown. The middle line of the box represents the median. The lower and upper line represent, respectively, the first and third quartiles, and the whiskers represent the range. Individual data points are superimposed on the boxplot. Agreement between the two platforms is shown for both Aβ isoforms (c–f). Scatter plots and Passing-Bablok regression analysis of plasma Aβ1–40 (c) and Aβ1–42 (d) concentrations measured by SIMOA Amyblood in function of their concentrations measured by ELISA. The regression line is shown in black. Spearman rank correlations were calculated to assess the non-linear relationship between the two methods for both isoforms. e, f Non-parametric percentile method of Bland-Altman graphically shows the agreement between the two immunoassay platforms for respectively Aβ1–40 (e) and Aβ1–42 (f). The solid red line represents the median of differences between measurements of the two methods from the same subject. The upper and the lower red dashed lines represent respectively the 97.5th and 2.5th percentile of the measurement differences between which 95% of measurements is situated. Aβ, β-amyloid; ELISA, enzyme-linked immunosorbent assay; SIMOA, single molecule array