Fig.2.
A) Effect of 0.05% detergent on the Aβ1-42 calibration curve. A representative calibration curve is presented. Each point of the curve is the mean of duplicate OD values. The addition of detergent (Tw20 or TrX100) to calibrators only reduced OD values, which can result in higher calculated analyte concentrations in CSF as compared to the use of calibrators without extra addition of a detergent (Results were confirmed several times). B) Effect of addition of detergent to ‘BIOTIN’ or in CSF collection tubes on CSF Aβ1-42 concentration. Addition of detergent to the “BIOTIN” component (= biotinylated antibody, incubated simultaneously with samples or calibrators) resulted in a reduction in OD values for samples and calibrators. In addition, CSF in which detergent was added at the time of collection showed higher OD values as compared to CSF without detergent. This was due to an effect on the equilibrium between protein-bound and free analyte in the biological matrix, resulting in higher analyte concentrations. As shown by the vertical lines, no difference in concentration is obtained when an assay with detergent in “BIOTIN” is compared to an assay performed without the addition of detergent, for each type of sample.