Finding the optimal cutoff value for amyloid β positivity using the iterative outlier method and concordance rate

Abstract

Purpose: The purpose of this study was to calculate the cutoff value for amyloid β (Aβ) positron emission tomography (PET) positivity using the iterative outlier method and to evaluate its validity based on the concordance rate. Methods: We performed the iterative outlier method on 373 cognitively unimpaired (CU) subjects and calculated the optimal cutoff value for Aβ positivity. The validation was performed using the independent dataset, comprising 83 subjects (27 CU, 27 amnestic mild cognitive impairment, and 29 Alzheimer's dementia). We evaluated the validity of the Aβ cutoff value by calculating its concordance rate with the visual assessment and between two different Aβ tracers performed in the same subject. Results: The concordance rate of Aβ cutoff values with the visual assessment ranged from 84.3% to 91.5%, depending on the reference regions. The concordance rate of the cutoff values between the two Aβ tracers ranged from 90.3% to 97.5%, all of which were higher than that of the visual assessment (86.7%). Conclusion:We demonstrated that the iterative outlier method could identify the cutoff value for Aβ PET positivity.

Comparison of automated quantification of amyloid deposition between PMOD and Heuron

“…Our predictive cutoff values for visual positivity of amyloid deposition were slightly higher than those obtained in previous similar studies (1.35) 16 , 17 . This difference could be attributed to our selection of the highest SUVR value in each target region for the ROC curve analysis, while the previous studies used the SUVR of global cerebral regions.…”

“…Regarding 18 F-flutemetamol, the activity of the pons is used as the standard for visual reading. Accordingly, previous studies have used the pons as a reference for quantitative analysis of PET images 17 – 19 . As the cerebellum has been used as a reference region in various brain PET images as well as amyloid PET analysis 20 – 22 , our institution used the cerebellar grey matter as a reference region for 18 F-flutemetamol.…”

Longitudinal amyloid cognitive composite in preclinical Alzheimer’s disease

“…A previous study reported that the visual assessment of Aβ PET showed high agreement with autopsy findings [46]. Another previous study from our group showed that visual assessment was highly concordant with the standardized uptake value ratio cutoff categorization for Aβ deposition [47,48].…”

“…So far, several clinical trials with antiamyloid medication did not reach statistical significance by a slight difference when using pri- [46]. Another previous study from our group showed that visual assessment was highly concordant with the standardized uptake value ratio cutoff categorization for Aβ deposition [47,48].…”

Independent effects of amyloid and vascular markers on long‐term functional outcomes: An 8‐year longitudinal study of subcortical vascular cognitive impairment

“…In cases of discordant results, we reached consensus through discussion. Florbetaben PET was considered Aβ-positive when rated as 2 or 3 according to the brain amyloid plaque load scoring system [19,20].…”