Immunoglobulin G Synthesis Rate, Cerebrospinal Fluid

Casandra

Casandra Test Code LC34046Version 1 (DRAFT)

Performing Lab

Lab LabcorpLab Test ID 085928CPT Codes 82040, 82042, 82784

Immunoglobulin G Synthesis Rate, Cerebrospinal Fluid

Clinical Use

Use

The Cerebrospinal Fluid IgG Synthesis Rate test evaluates the production rate of Immunoglobulin G (IgG) in the central nervous system (CNS). It is primarily used to diagnose inflammatory and autoimmune diseases affecting the CNS, such as multiple sclerosis. The test calculates the IgG synthesis rate using measurements of IgG and albumin in both serum and spinal fluid. It helps in determining whether increased levels of IgG in the CNS are due to local synthesis or systemic elevations followed by passive transfer across the blood-brain barrier.

Special Instructions

The test employs an empirically-derived formula, validated through radiolabeled experiments, to estimate IgG production by the CNS. The process takes into account the ratio of average normal serum IgG to CSF IgG. An intact blood-brain barrier is assumed in this calculation, which is noted in the formula applied for synthesizing data.

Limitations

The validity of the IgG synthesis formula is dependent on the assumption that an intact blood-brain barrier governs the proportion of IgG passing into the CSF. The test results must be correlated with clinical findings as the diagnosis of diseases like multiple sclerosis remains a clinical neurologic one. There can be cases where the CNS IgG synthesis rate is normal even in the presence of neurological conditions, therefore sensitivity and specificity metrics should be evaluated alongside clinical contexts.

Test Details