Comparison of CSF to serum levels of IgG may indicate increased synthesis of antibody within the central nervous system.
CSF-to-serum IgG index =
= (CSF IgG in mg/dL) / (serum IgG in g/dL)
Interpretation:
• The normal range is 3-8; if the CSF IgG is expressed in g/dL, the normal value is 0.003-0.008
• Increases in the index can occur with increased synthesis of immunoglobulin within the CSF, or leakage due to impairment of the blood-brain barrier
Limitations
• A traumatic CSF tap results in a false elevation of the index.
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Specialty: Immunology/Rheumatology
