Chip Electrophoresis as a Method for Quantifying Total Albumin in Cerebrospinal Fluid

Abstract

The cerebrospinal/serum albumin ratio ( QAlb) is a measure of cerebrospinal—blood barrier permeability, where dysfunctional barriers have been associated with a variety of disease states. Thus, the ability to accurately quantify albumin has critical diagnostic importance. The current work uses chip electrophoresis as an alternative methodology to the conventional immunoassay for quantifying cerebrospinal fluid (CSF) albumin. With variable concentrations of bovine serum albumin normalized to a chicken albumin internal standard, the electrophoresis system demonstrated signal correlation with a best-fit polynomial ( R2 = 0.9993) (concentration range of 7.8–1000 mg/L). Interchip and intrachip variation studies conducted on patient CSF demonstrated coefficient of variations of 0.1–17%. Chip electrophoresis detected an average of 24% greater albumin than the immunoassay in patient CSF samples (n = 58), indicating the ability to detect immunoreactive and non-immunoreactive forms of albumin. Finally, the correlation of CSF albumin concentration to QAlb determined by chip electrophoresis ( r2 = 0.8683) was comparable with that determined by immunoassay ( r2 = 0.8390). Therefore, this work demonstrates proof-of-principle that chip electrophoresis can serve as an alternative method for quantifying total (immunoreactive and non-immunoreactive) albumin in CSF.