What determines the CSF concentrations of albumin and plasma-derived IgG?

To estimate the mean influence of the main determinants of the cerebrospinal fluid (CSF) concentration of albumin and plasma-derived immunoglobulin G (IgG).

Correlations of serum and CSF concentrations of albumin and IgG and assumptions of the mode of action of the determinants (plasma concentration, barrier permeability, and CSF flow) are used to quantify the determinants' influences in a sample of 1700 patients.

We estimated in patients with normal CSF albumin that the serum concentrations of albumin and IgG explained 3.3% and 23% of the variation of the respective CSF concentrations, whereas the barrier permeability accounted for 41.9% and 22.2%, and CSF flow for 54.8%. In patients with pathologic CSF albumin concentration, the serum concentrations were estimated to explain 0.2% and 8.2% of the variation of the respective CSF concentrations, the barrier permeability 19.7% and 11.7%, and CSF flow 80.1%.

CSF flow had the strongest mean influence, especially at elevated CSF albumin levels. The serum concentrations and barrier permeabilities of albumin and IgG influenced the respective CSF concentrations quite differently, which should be due to the different physicochemical properties of the two molecules. Mean influences from large patient samples, as explored here, can give only an overview. Understanding the determinants in individuals will need further specific measurements, especially of CSF flow.