Protein Electrophoresis Spinal Fluid

94 Since cerebrospinal fluid (CSF) is an ultrafiltrate of plasma, it has much lower concentrations of the highest molecular weight proteins such as IgG, IgA and IgM. Elevated CSF IgG levels can either be the result of diffusion of plasma IgG across an altered blood brain barrier or intrathecal synthesis. Patients with multiple sclerosis and other demyelinating disorders often have elevated CSF IgG concentrations due to intrathecal synthesis. One of the best methods to detect intrathecal IgG synthesis has been to examine CSF for the presence of oligoclonal bands after separation of proteins by electrophoresis. IgG in normal CSF migrates as a faint diffuse zone, but in demyelinating diseases, IgG migrates as discrete oligoclonal bands. During the summer of 2003, the FDA approved a new method for the detection of oligoclonal bands that uses isoelectric focusing plus immunofixation (IEF) instead of electrophoresis. The Consortium of Multiple Sclerosis Centers has endorsed IEF because of its increased sensitivity (>95%). With IEF, oligoclonal bands may be detected while the total CSF IgG concentration is still within the normal range.

Oligoclonal bands are reported as present when they are seen in CSF but not in serum or when they are present in greater number in the CSF than in the serum. Therefore, in order for the pathologist to interpret the results, a red top tube of blood must accompany all CSF specimens submitted for a multiple sclerosis profile.

Electrophoresis is performed to determine the CSF protein pattern. A normal CSF protein electrophoretic pattern has relatively more prealbumin, less alpha 2 globulin, and less gamma globulin than serum from the same individual. Albumin and beta bands appear similar to serum. If a multiple sclerosis panel is ordered, isoelectric focusing is also performed to detect oligoclonal bands. Oligoclonal bands are normally absent.

Reference ranges are:

Total protein	15 - 60 mg/dL
Prealbumin	1 - 8%
Albumin	50 - 80%
Alpha 1 globulin	2 - 8%
Alpha 2 globulin	2 - 12%
Beta globulin	8 - 18%
Gamma globulin	3 - 12%
Oligoclonal bands	absent

Specimen requirement is 1 mL of spinal fluid.

Last Updated on Monday, 18 July 2011