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Fig. 5 | Alzheimer's Research & Therapy

Fig. 5

From: Towards a unified protocol for handling of CSF before β-amyloid measurements

Fig. 5

Blood contamination—MSD assays. Aβ42MSD (a), Aβ40MSD (b), and Aβ42/Aβ40MSD (c) in CSF samples with added blood stored at either RT or 4 °C for up to 2 weeks after collection. Aβ42MSD (d), Aβ40MSD (e), and Aβ42/Aβ40MSD (f) in CSF samples with added blood stored at − 20 °C for 2 weeks after collection. CSF was collected from 7 to 10 patients per experimental condition, 24 CSF tubes per patients. Data are shown as the percentage of biomarker levels in neat CSF samples (from the same donor) that were treated the same way with respect to other experimental conditions (centrifugation, temperature, and time). The effects of pre-analytical factors were tested using mixed-effects model including participant identification as a random effect and treatment groups (temperature, centrifugation, and blood contamination), time, and time × treatment group interactions as fixed factors. The gray areas represent 90–110% range that was set based on the inter-assay CVs as described in the “Materials and methods” section. Only changes in the mean biomarker levels outside this range (gray area) were considered to be due to pre-analytical sample handling and examined using post hoc tests. *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001. c Because of the very low levels of CSF Aβ42 and Aβ40 (< 10 pg/ml), we did not calculate the Aβ42/Aβ40 ratio for non-centrifuged CSF-10%-blood samples that were stored at RT for 1–2 weeks. Horizontal lines and error bars represent mean ± SEM. Abbreviations: Aβ, β-amyloid; EI, EUROIMMUN; h, hours; MSD, Mesoscale discovery; RT, room temperature; SEM, standard error of mean

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