Protein in cerebrospinal fluid (CSF)

Norm
Adults 0.15–0.60 g/l
Children
up to 1 month 0.15–1.50 g/l
1–6 months 0.15–1.00 g/l

1. Protein Composition in Cerebrospinal Fluid (CSF)

   The qualitative protein composition in cerebrospinal fluid (CSF) is similar to that found in serum. The major difference is that prealbumin is higher in CSF. Additionally, the absolute protein concentration in CSF is much lower than in serum, approximately 15 times lower. The ratio of albumins to globulins in adult CSF is 2:1. However, in the first year of life, this ratio changes to 1:1.

   Pathology Indicators

   Sometimes, pathology is indicated not only by a significant increase in protein concentration but also when the protein concentration is at the upper limit of the normal range (0.40–0.60g/l). An increase in protein concentration may also result from blood contamination during cerebrospinal fluid (CSF) sampling. To assess blood contamination, determine the number of erythrocytes in both the CSF and blood simultaneously. If the increase in protein concentration in the CSF is proportional to the erythrocyte count, then peripheral blood contamination is likely. In cases of traumatic blood contamination at the time of collection, the laboratory can separate erythrocytes through centrifugation.

   Further Investigation

   This rule is not absolute. Therefore, patients with increased CSF protein concentration should undergo further investigation to determine other indicators, such as IgG oligoclonal bands and the IgG/albumin index. Oligoclonal IgG bands are a sign of multiple sclerosis. For protein electrophoresis, the concentration of the CSF is required.

   Diagnostic Priorities for Meningitis

   If there is little CSF available when diagnosing meningitis, priorities for indicators should be established:

   1. Culture
   2. Smear, stained by Gram method
   3. Cytosis
   4. Determination of protein and glucose concentrations

Source | Handbook of Basic Laboratory Tests | Doctor of Medical Sciences Gintaras Zaleskis