Fig. 4

Blood contamination—EI assay. a Aβ42^EI in CSF samples with added 0.1% or 10% blood stored at either RT or 4 °C for up to 2 weeks after collection (4 patients, 12 CSF tubes per patient; except the 10% blood, 4 °C, centrifugation group from where one sample was excluded due to the technical error during the Aβ42 measurements). b Aβ42^EI in CSF samples with added 0.01%, 0.02, or 0.04% blood stored at RT for up to 1 week after collection (4 patients, 8 CSF tubes per patient). 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 gray areas represent 95–105% range that was set based on the inter-assay CVs as described in the “Materials and methods” section. Given the small number of participants, statistical tests were not performed. Horizontal lines and error bars represent mean ± SEM. Abbreviations: Aβ, β-amyloid; EI, EUROIMMUN; RT, room temperature; SEM, standard error of mean