Fig. 3

Correlations between immunoassay- and mass spectrometry-derived concentrations of p-tau in the BioFINDER-2 cohort. Top: Black lines of origin along the horizontal depict a theoretical linear relationship between variables without over- or under-estimation. The regression line and corresponding 95% confidence intervals below the origin indicates that mass spectrometry p-tau₁₈₁ measurements underestimate p-tau concentrations from immunoassay measurements, which was not observed for p-tau₂₁₇ or p-tau₂₃₁. Bottom: Bland–Altman analysis assessing bias between mass spectrometry and immunoassay measurements of p-tau. Dashed lines indicate limits of agreement, which correspond to standard deviation of the bias multiplied by 1.96. P-tau₂₃₁ had the largest bias, followed by p-tau₁₈₁ and p-tau₂₁₇ with the smallest bias. Z-scores for each biomarker are represented to facilitate comparisons between measurements. MS = Mass spectrometry