TABLE 5.

Percent reduction of Aβ PET scans for varying prevalence rates based on the BHR online prediction model in CU and MCI participants

Prevalence	PPV	N of Aβ+ predicted by online BHR model	Aβ PET scans needed without prescreen	N of Aβ PET scans saved	% reduction of unnecessary PET scans
30.0%	39.3%	509	667	158	23.7%
35.0%	44.9%	446	571	126	22.0%
40.0%	50.2%	398	500	102	20.3%
45.0%	55.3%	362	444	83	18.6%
50.0%	60.2%	332	400	68	16.9%
55.0%	64.9%	308	364	55	15.2%

Abbreviations: Aβ, amyloid beta; BHR, Brain Health Registry; CU, cognitively unimpaired; MCI, mild cognitive impairment; PET, positron emission tomography; PPV, positive predictive value.

Notes: The calculations are based on a hypothetical trial which aims to identify 200 Aβ+ older adults. For calculating the PPV by prevalence, the sensitivity = 65% and specificity = 57% from the combined online BHR model in the CU and MCI group were used (Section 3.3).