53 E ect of flow on longitudinal tau PET To adhere to the typical duration of clinical trials in AD, we calculated percentage change over an 18-mo period and used those SDs as input for the sample size calculations. Simulations Details on the methods used for simulations can be found in the Methods section of the supplemental materials. RESULTS Patient characteristics are shown in Table 1. In both AD and SCD, 18F-flortaucipir SUVr were higher than DVR for all regions and at both time points (baseline and follow-up, all P < 0.001). Respective DVR, SUVr, and R1 values are shown in Table 2 (SCD subjects and AD patients) and Supplementary Tables 2 and 3 (Aβ-negative and -positive SCD subjects, respectively). The percentage overestimation of SUVr relative to DVR, for all regions and at both time points, is presented in Supplementary Table 4. Annualized percentage change in DVR and SUVr is presented in Supplementary Tables 5 and 6. No significant correlations between DVR or SUVr and R1 were observed in either SCD or AD patients (Supplementary Figure 1). Partial-volume-corrected data yielded essentially similar results; therefore, only noncorrected data will be presented further in the article. Table 1. Demographics of the study population. SCD (n=38) AD (n=24) Female/male, n 16/22 11/13 Age at baseline, y 65 ± 7 66 ± 7 Age at follow-up, y 67 ± 7 68 ± 7 Time between PET scans, y 2.1 ± 0.3* 2.2 ± 0.3* MMSE at baseline 29 ± 1* 24 ± 3* Amyloid positivea at baseline, n 12/38* 24/24* Amyloid positivea at follow-up, n 16/38* NA APOE4 allele carriers, n 12/38* 17/22 (2 unknown)* *Significant differences (p<0.05) between diagnostic groups. aSCD subjects were classified as amyloid positive as evidenced by substantial Aß pathology after SUVr50-70min 18F-florbetapir Aß-PET scan visual assessment and MCI/AD patients were classified as amyloid positive as evidenced by CSF biomarkers for AD (i.e. CSF Aß1-42 < 813 ng/L) and/or a positive Aß-PET ( 18F-PiB or 18F-florbetaben) scan by visual assessment. MMSE = mini mental state examination. NA = not available. Mean ± SD are provided, unless otherwise indicated. 3
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