Is plasma amyloid-β 1–42/1–40 a better biomarker for Alzheimer’s disease than AβX–42/X–40?

Table 2 Amyloid-β isoform levels and Aβ42/40 ratios in amyloid-positive and amyloid-negative subjects

	Variable	Median of Aβ⁻	MAD^a of Aβ⁻	Median of Aβ⁺	MAD^a of Aβ⁺	P-value^b
CSF	AβX–40	5777.11	1525.46	6283.72	2095.14	0.51
	AβX–42	500.46	128.56	198.00	84.20	1.04E–13
	AβX–42/X–40	0.083	0.003	0.033	0.005	2.08E–13
	Aβ1–40	5224.52	1361.74	5576.23	1686.43	0.43
	Aβ1–42	523.75	133.87	230.40	82.55	1.20E–13
	Aβ1–42/1–40	0.100	0.006	0.044	0.007	2.08E–13
Plasma IP-eluate	AβX–40	301.93	58.61	300.30	60.42	0.37
	AβX–42	23.67	5.95	18.68	3.24	2.14E–04
	AβX–42/X–40	0.077	0.008	0.065	0.006	3.67E–08
	Aβ1–40	145.67	30.88	142.96	33.32	0.55
	Aβ1–42	15.91	3.96	12.23	2.56	1.76E–04
	Aβ1–42/1–40	0.111	0.013	0.088	0.009	1.77E–08

Aβ amyloid-β, CSF cerebrospinal fluid, IP immunoprecipitation
^aMAD: median absolute deviation scaled with factor 1.4826
^bTwo-tailed Mann–Whitney test (Wilcoxon rank sum test) p-value for the comparison between the amyloid-negative (Aβ⁻, CSF AβX–42/X–40 > 0.058, n = 37) and amyloid-positive (Aβ⁺, CSF AβX–42/X–40 ≤ 0.058, n = 36) groups. Due to the exploratory character of the study, p-values were not corrected for multiple comparisons

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