Comparison of protein concentrations in serum versus plasma from Alzheimer’s patients

Abstract

Background: There is great interest in develop- ing blood-based biomarkers for Alzheimer’s dis- ease (AD); however, there is no consensus as to what blood fraction is most appropriate for ana- lyzing particular markers. The current study pro- vides empirical evidence regarding how blood- based proteins vary depending on whether they are assayed in serum or plasma. Methods: We analyzed concentrations of 100 proteins in mat- ched samples of serum and plasma from 39 Caucasian AD participants from the Texas Alz- heimer’s Research and Care Consortium by mul- tiplex immunoassay. Results: Concentrations of 40 proteins were highly correlated (r2 ≥ 0.75) between plasma and serum while the remaining proteins were moderately to weakly correlated (r2 < 0.75). Discussion: Whether plasma vs. se- rum is assayed can have a large impact on the observed concentration of some proteins, in- cluding several proteins that are of great interest to AD pathophysiology. The current findings may explain the significant discrepancies often- times reported in the AD biomarker field.