Table 1 Demographics of study participants.

	IP-MS-WashU (n = 120)					IA-Elc (n = 121)
	PET−/ plasma−	PET−/ plasma+	PET+/ plasma−	PET+/ plasma+	p-value	PET−/ plasma−	PET−/ plasma+	PET+/ plasma−	PET+/ plasma+	p-value
No. (%)	45 (38)	16 (13)	10 (8)	49 (41)		35 (29)	27 (22)	8 (7)	51 (42)
Age, y	75 (72, 81)	77.5 (71, 79)	80 (77, 82)	79 (75, 84)	0.097	76 (72, 81)	77 (71, 80)	76 (74, 80)	80 (75, 83)	0.034
Male (%)	22 (49)	13 (81)	5 (50)	29 (59)	0.148	19 (54)	17 (63)	4 (50)	30 (59)	0.875
Education, y	18 (14, 18)	18 (15.5, 19)	18 (16, 18)	16 (12, 20)	0.557	18 (16, 19)	16 (14, 18)	15 (14, 18)	16 (13, 18)	0.207
APOE ε4 carrier (%)	11 (24)	8 (50)	3 (30)	26 (53)	0.026^a	10 (29)	10 (37)	4 (50)	25 (49)	0.258
Time interval between PET and plasma, d	0 (−7.5, 2)	0 (−18, 2.5)	0 (−8, 1)	0 (−6, 4.5)	0.881	0 (−7.5, 2)	0 (−18, 2.5)	0 (−8, 1)	0 (−6, 4.5)	0.881
Plasma Aβ42/40	0.14 (0.13, 0.14)	0.12 (0.12, 0.12)	0.13 (0.13, 0.14)	0.12 (0.12, 0.12)	<0.001^b	0.18 (0.17, 0.19)	0.15 (0.14, 0.16)	0.18 (0.17, 0.18)	0.15 (0.14, 0.16)	<0.001^d
Amyloid PET SUVR	0.98 (0.91, 1.02)	1.02 (0.98, 1.06)	1.23 (1.16, 1.38)	1.33 (1.28, 1.47)	<0.001^c	0.97 (0.93, 1.05)	1.01 (0.96, 1.02)	1.22 (1.15, 1.44)	1.33 (1.25, 1.46)	<0.001^e

Abbreviations: Aβ amyloid-β, IA-Elc Elecsys immunoassay from Roche Diagnostics, IP-MS-WashU immunoprecipitation followed by mass spectrometry method developed at Washington, IQR interquartile range, PET positron emission tomography, SUVR standardized uptake value ratio.
Data are shown as median (IQR) unless otherwise specified.
Post-hoc analysis:
^aAPOE ε4 carrier: PET−/plasma− < PET+/plasma+: odds ratio = 3.44 [95% CI: 1.33–9.37], p = 0.036.
^bPlasma Aβ42/40: PET−/plasma− < PET−/plasma+: Z = 5.746, p < 0.001, PET−/plasma+ < PET+/plasma−: Z = −3.89, p < 0.001, PET−/plasma− < PET+/plasma+: Z = 8.596, p < 0.001, PET+/plasma− < PET+/plasma+: Z = 4.72, p < 0.001.
^cAmyloid PET SUVR: PET−/plasma− < PET+/plasma−: Z = −4.277, p < 0.001, PET−/plasma+ < PET+/plasma−: Z = −2.997, p = 0.004, PET−/plasma− < PET+/plasma+: Z = −9.020, p < 0.001, PET−/plasma+ < PET+/plasma+: Z = −5.470, p < 0.001.
^dPlasma Aβ42/40: PET−/plasma− < PET−/plasma+: Z = 6.670, p < 0.001, PET−/plasma+ < PET+/plasma−: Z = −3.961, p < 0.001, PET−/plasma− < PET+/plasma+: Z = 8.045, p < 0.001, PET+/plasma− < PET+/plasma+: Z = 4.344, p < 0.001.
^eAmyloid PET SUVR: PET−/plasma− < PET+/plasma−: Z = −3.988, p < 0.001, PET−/plasma+ < PET+/plasma−: Z = −3.708, p < 0.001, PET−/plasma− < PET+/plasma+: Z = −8.135, p < 0.001, PET−/plasma+ < PET+/plasma+: Z = −7.208, p < 0.001.

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