Table 3.

Comparison among fluid biomarkers on predicting tau PET positivity in cognitively impaired patients with in-bag estimates

Single-cutoff approach
	Accuracy		PPV		NPV		Sensitivity
	Mean	Difference	Mean	Difference	Mean	Difference	Mean	Difference
Plasma %p-tau217	0.88 (0.85, 0.91)	Ref.	0.88 (0.86, 0.90)	Ref.	0.88 (0.82, 0.94)	Ref.	0.86 (0.78, 0.93)	Ref.
CSF p-tau/Aβ42	0.82 (0.76, 0.87)	0.06 (0.01, 0.12)	0.86 (0.83, 0.89)	0.02 (0.00, 0.04)	0.79 (0.72, 0.87)	0.09 (0.01, 0.16)	0.72 (0.60, 0.84)	0.14 (0.02, 0.25)
CSF Aβ42/40	0.68 (0.62, 0.76)	0.20 (0.14, 0.26)	0.79 (0.73, 0.84)	0.10 (0.05, 0.15)	0.65 (0.59, 0.72)	0.24 (0.16, 0.31)	0.42 (0.31, 0.57)	0.44 (0.29, 0.56)

Two-cutoffs approach
	Accuracy		PPV		NPV		Number of intermediate participants
	Mean	Difference	Mean	Difference	Mean	Difference	Mean	Difference*
Plasma %p-tau217	0.94 (0.94, 0.95)	Ref.	0.93 (0.92, 0.94)	Ref.	0.95 (0.94, 0.96)	Ref.	19.5 (11.6, 27.5)	Ref.
CSF p-tau/Aβ42	0.93 (0.92, 0.94)	0.01 (0.00, 0.02)	0.90 (0.85, 0.92)	0.04 (0.01, 0.08)	0.95 (0.94, 0.96)	0.00 (−0.01, 0.01)	34.0 (24.1, 42.8)	0.14 (0.04, 0.24)
CSF Aβ42/40	0.91 (0.89, 0.92)	0.03 (0.02, 0.05)	0.81 (0.68, 0.88)	0.12 (0.06, 0.25)	0.94 (0.94, 0.95)	0.01 (0.00, 0.02)	49.1 (41.9, 57.0)	0.30 (0.20, 0.39)

Comparison estimates among fluid biomarkers on predicting tau PET positivity in cognitively impaired patients from the BioFINDER-2 cohort. For the single-cutoff approach, the cutoffs of fluid biomarkers were derived by maximizing sensitivity and fixing specificity at 90% against each imaging outcome. For the two-cutoffs approach, the lower cutoff was obtained by maximizing specificity with sensitivity fixed at 95%, whereas the upper cutoff was obtained by maximizing sensitivity and fixing specificity at 95%. Participants who fall between these two cutoffs were classified in the intermediate group. Differences between the statistics using plasma %p-tau217 (reference) and CSF biomarkers are shown together with the mean values. We considered plasma and CSF biomarkers clinically equivalent if the 95% CI of the mean difference included zero and clinically superior if it did not include zero and favored plasma (>0). *Differences in the number of participants in the intermediate group were scaled to a maximum of 1 to be comparable with the other differences. Tau PET positivity was assessed using an in-house previously validated cutoff (SUVR > 1.32 for both cohorts in Braak I–IV). CSF, cerebrospinal fluid; NPV, negative predictive value; PPV, positive predictive value; SUVR, standardized uptake value ratio; CI, confidence interval