Fig. 4.

Relationship between immunoassay- and mass spectrometry-derived concentrations of p-tau with amyloid-PET and tau-PET in the TRIAD cohort. Scatterplots represent associations between p-tau181 (left), p-tau217 (middle) and p-tau231 (right) measured using both immunoassay and mass spectrometry with amyloid-PET (A), tau-PET (B). Correlation coefficients are presented as Spearman’s rho. P-tau₁₈₁ measured with mass spectrometry had significantly lower correlations with both amyloid-PET and tau-PET than when measured with immunoassay (p < 0.001), whereas no differences were observed for p-tau₂₁₇ or p-tau₂₃₁. For p-tau₁₈₁ measured with Mass Spectrometry, one data point (y = 119.4 fmol/ml) is not visually displayed to fit the axes on a comparable scale; this data point was nonetheless included in all analyses. A summary of all correlations, as well as comparisons between immunoassay and mass spectrometry is presented in Table 5