Clinical and analytical comparison of six Simoa assays for plasma P-tau isoforms P-tau181, P-tau217, and P-tau231

Table 2 Clinical performance of the six P-tau assays

	AD dementia	Controls	Differentiation AD dementia versus controls
	Median [IQR]	Median [IQR]	Fold change	AUC (95% CI)	Cutoff	%Sens	%Spec
P-tau181 Eli Lilly	11.1 [10.4–13.6]	6.1 [5.1–7.4]	1.8	0.938 (0.872–1.000)	8.6	100	89
P-tau181 ADx	37.6 [28.8–48.6]	13.2 [10.3–17.6]	2.9	0.988 (0.969–1.000)	24	100	92
P-tau181 Quanterix	3.4 [2.7–4.1]	1.6 [1.4–2.2]	2.0	0.936 (0.885–0.987)	2.2	100	78
P-tau217 Eli Lilly	0.7 [0.6–0.9]	0.17 [0.14–0.2]	4.1	0.995 (0.987–1.000)	0.42	92.5	100
P-tau231 ADx	7.3 [5.6–9.1]	5.5 [4.5–6.9]	1.3	0.719 (0.607–0.831)	4.7	95	43
P-tau231 Gothenburg	15.3 [13.9–19.8]	10.3 [8.9–11.9]	1.5	0.943 (0.896–0.991)	13.4	89	90

Median concentrations are in pg/mL. Fold change was calculated by dividing the median concentration in the AD dementia group over the median concentration in the control group. AUCs were derived from ROC analysis. All group comparisons were significant with p values below the Bonferroni-adjusted p value cutoff of 0.0083. P-tau cutoff was specified at the Youden’s indeces (maximum sum of sensitivity and specificity)
P-tau Phosphorylated tau, AD Alzheimer’s disease, IQR: Interquantile range, AUC Area under the curve, sens Sensitivity, spec Specificity

ISSN: 1758-9193