Table 3.

Projected impact of applying Aβ probability algorithms for the 14.9 million US patients aged ≥55 years projected to screen positive for MCI^∗

Scenario	RAND report projected number	Applying algorithm†
		≥0.6 Probability threshold		≥0.5 Probability threshold		≥0.4 Probability threshold
	(No algorithm)	Age, recall	With APOE ε4	Age, recall	With APOE ε4	Age, recall	With APOE ε4
Send to Aβ confirmation	6.7 M	5.1 M	4.0 M	7.7 M	8.0 M	9.9 M	10.0 M
Confirmed (true + sent)	3.0 M	3.6 M	3.1 M	5.0 M	5.5 M	6.1 M	6.4 M
Not confirmed (false + sent)	3.7 M	1.5 M	0.9 M	2.7 M	2.5 M	3.8 M	3.6 M

Abbreviations: Aβ, amyloid β; APOE, apolipoprotein E.

^∗Projected numbers obtained from the RAND report for US health care system readiness for an Alzheimer's disease–modifying therapy; projections for five European countries were of similar magnitude, with an estimated 14.3 M patients in those health care systems screening positive for mild cognitive impairment (data not shown) [8,9].

^†Algorithm listed as “age, recall” uses age and recall z-scores. Algorithm listed as “with APOE ε4” uses age, recall z-score, and APOE ε4 positive status. Values in the “send to Aβ confirmation” row refer to patients who would be predicted positive with the algorithm for a given threshold for probability (e.g., as displayed in table: 0.6, 0.5, and 0.4 probability). Values are derived from the performance of the algorithms in the Mayo Clinic Study of Aging validation data set using Rey Auditory Verbal Learning Test immediate recall z-score.