Biomarker

Intracenter scheme^{a}

Intercenter scheme^{b}


CV (%)^{c}

\( \frac{\sqrt{\psi }}{\mu } \) (%)

\( \frac{\sqrt{\theta }}{\mu } \) (%)

ICC

CV (%)^{c}

\( \frac{\sqrt{\psi }}{\mu } \) (%)

\( \frac{\sqrt{\theta }}{\mu } \) (%)

ICC


Aβ1–42

12

< 0.1

12

< 0.01

31

28

10

0.89

pTau181

3.2

3

0.8

0.93

8

2.5

7

0.11 (0.88)^{d}

Albumin

4

< 0.1

4

< 0.01

10

2

9

0.05 (0.92)^{d}

 μ represents overall average concentration of a given biomarker in a given scheme
 Aβ amyloid beta, PPS proficiency processing sample, SA secondary sample
 ^{a}In the intracenter scheme, betweencluster (random intercept) variability (ψ) was the variability of the results obtained from 10 PPSs, and withincluster (residual) variability (θ) was the variability of the results obtained in two SAs prepared from each PPS
 ^{b}In the interlaboratory scheme, betweencluster (random intercept) variability (ψ) was the variability of the results obtained from 10 PPSs sent to the participating laboratories, and withincluster (residual) variability (θ) was the variability of the results obtained in two SAs prepared in each laboratory from the PPS
 ^{c}Unadjusted total coefficient of variation of the results of the measurements of 20 SAs treated as 20 independent samples, irrespective of their origin from the PPSs
 ^{d}ICCs after exclusion of the two centers (numbers 7 and 8) with apparent failure in their standardized operating procedures