Agreement of CSF. cutoffs with amyloid quantification We next processed amyloid PET scans to obtain quantification values of amyloid deposition. In our study, the previously validated SUVR value of 1.11[29], showed 83% PPA, 76% NPA, and 81% OPA with visual classification. As displayed in Supplementary Figure 3, scans that were divergently classified as "negative" or "positive" by one of the three raters showed intermediate SUVR values compared to scans that were unanimously classified. As seen in Figure 4, the agreement of CSF cutoffs with amyloid PET quantification was similar to that with visual classification for all individual biomarkers and ratios. We studied the correlation between each CSF biomarker and global amyloid accumulation by fitting quadratic linear models. In these models, the adjusted coefficients of determination (R2) for individual biomarkers were 0.22 for Aβ1-42 (p<0.001), 0.03 for Aβ1-40 (p=0.06), 0.27 for tTau (p<0.001) and 0.38 for pTau (p<0.001). The adjusted coefficients of determination were higher for all ratios compared to individual biomarkers. The combination of Aβ1-42 with Aβ1-40 increased R2 value to 0.44 (p<0.001), indicating that this ratio reflects the amyloid deposition better than Aβ1-42 alone. Stratified analysis by 18F-Florbetapir visual status showed lower R2 values for all biomarkers, which suggests that the correlation observed between CSF biomarkers and amyloid PET quantification is partially mediated by an amyloid-status or diagnostic effect. In this stratified analysis, the highest correlation of SUVR values was found with the Aβ1-42/Aβ1-40 ratio in the amyloid-negative group (R2=0.42; p<0.001).
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Samples: Positive Percent Agreement, Positive Percent Agreement, Positive Percent Agreement
