Blood-brain barrier damage restricts the reliability of quantitative formulae and isoelectric focusing in detecting intrathecally synthesized IgG.
The demonstration of intrathecally synthesized IgG constitutes one of the most important aids in the diagnosis of multiple sclerosis (MS). This can be done either by the application of empirical formulae or by analytical electrophoretic migration of IgG. However, all methods are influenced by the presence of blood-brain barrier (BBB) damage, as confirmed by the present study. We compared the results achieved by the application of 3 formulae (IgG index, intra-BBB IgG synthesis rate, IgG hyperbolic function) to those by isoelectric focusing (IEF) of unconcentrated cerebrospinal fluid (CSF). The most reliable method to detect intrathecal IgG production was IEF followed by specific immunofixation; even so, this method was subjected to pitfalls due to BBB damage. All formulae gave incorrect and misleading results, especially in case of BBB damage. Therefore, this limiting factor should be considered when formulae are used for clinical purposes.
D000293:Adolescent; D000328:Adult; D001812:Blood-Brain Barrier; D005260:Female; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000134:cerebrospinal fluid*; D007142:Immunoglobulin gamma-Chains / Q000032:analysis / Q000134:cerebrospinal fluid*; D007525:Isoelectric Focusing / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000097:blood / Q000276:immunology* / Q000503:physiopathology
D007143:Immunoglobulin Heavy Chains; D007142:Immunoglobulin gamma-Chains