Albumin in cerebrospinal fluid

The simplest method is the calculation using the Delpech-Lichtblau quotient, which is based on parallel determinations of concentrations of IgG and albumin in cerebrospinal fluid and serum. The mathematical structure of the formula is as follows ... 

The albumin quotient is the most precise, routinely used criterion for assessment of the function of the blood-CSF barrier because albumin in cerebrospinal fluid originates exclusively from serum. Its parallel determination during the monitoring of any CSF protein is necessary because this is the only way to differentiate its increased concentration in cerebrospinal fluid due to passive penetration of the respective serum protein from a more specific increase in the concentration of the monitored protein. It is based on its intrathecal synthesis or on a specific transport mechanism for the given protein across the blood-CSF barrier. Unfortunately, some clinicians disregard this recommendation, and this elementary fact is not sufficiently emphasized in publications on cerebrospinal fluid (A22). 

During the monitoring of any protein in cerebrospinal fluid, it is necessary to bear in mind the functional status of the blood-CSF barrier, serum concentration of the respective protein, and the dimensions of the molecule (or the information based on the molecular weight). These data principally influence the resulting concentration in cerebrospinal fluid. It must also be emphasized again that the parallel determination of albumin in cerebrospinal fluid and serum is necessary. 

---