IgG, Quant, CSF

Laboratory assay overview

The IgG Synthesis Rate/Index is useful in diagnosing and monitoring patients with multiple sclerosis and other inflammatory diseases involving the brain and meninges.

Laboratory assay overview

This test may be helpful in the evaluation of intrathecal synthesis of IgG in individuals with clinical suspicion of inflammatory diseases of the central nervous system (CNS), especially multiple sclerosis [1]. Intrathecal synthesis of IgG can be more specifically demonstrated by paring IgG/albumin ratios in the cerebrospinal fluid (CSF) and serum to calculate IgG index [2]. Elevated IgG levels in the CSF may be caused by increased intrathecal synthesis of IgG, increased permeability of blood-brain barrier, or both. Because albumin is not synthesized or metabolized in the CSF, it can be used to evaluate the permeability of the blood-CSF barrier. To demonstrate intrathecal synthesis of IgG specifically, IgG and albumin levels in the CSF and serum can be used to calculate IgG index [1]. In patients with multiple sclerosis, intrathecal synthesis of IgG may be evaluated with several assays. IgG/albumin ratio in the CSF may be elevated in about 70% of the patients. IgG index, calculated with paired IgG/albumin ratios in the CSF and serum, may be elevated in about 80% of patients. Oligoclonal bands may be detected in up to 95% of the patients [1-3]. Intrathecal synthesis of IgG may also be caused by other CNS inflammatory diseases, such as chronic meningoencephalitis, subacute sclerosing panencephalitis, and Guillain-Barre syndrome [1]. The results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings. References 1. Johnson AM, et al. Amino acids, peptides, and proteins. In: Burtis CA, et al. eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 4th ed. Elsevier Inc; 2006:578-580. 2. Hershey LA, et al. Ann Neurol. 1980;8(4):426-434. 3. Giesser BS. Neurol Clin. 2011;29(2):381-388.

Quest Diagnostics population reference ranges

Quest Diagnostics calculates these statistical intervals for this specific assay and demographic group, not as universal optimal targets.

Laboratory assay overview

Detect and measure the level of IgG production by the central nervous system; has been applied to the diagnosis of multiple sclerosis along with CSF IgG synthesis rate and CSF immunoglobulin “oligoclonal” bands

Laboratory assay overview

Evaluate the de novo rate of synthesis of IgG in CNS; diagnose inflammatory and autoimmune diseases involving CNS, in particular, multiple sclerosis; determine if IgG synthesis rate is based on the quotient of average normal serum IgG/average normal CSF IgG

Laboratory assay overview

Evaluate central nervous system involvement by infection, neoplasm, or primary neurologic disease (in particular, multiple sclerosis)

Laboratory assay overview

This panel may be ordered to assist in the initial diagnosis and subsequent management of inflammatory, infectious, autoimmune, neoplastic, or other immune-mediated disorders affecting the nervous system. Quantitative values for IgM, IgG, and IgA will be reported [1]. Immunoglobulins, or antibodies, are proteins made by the immune system in response to an infection or other potential threat. Immunoglobulins come in various forms (IgM, IgG, IgA, and others) and have unique properties and functions to coordinate the body’s response [1]. A serum-based immunoglobulin panel (test code 7083) can also be used to evaluate conditions associated with abnormal immunoglobulin levels; however, this test, which uses CSF as the sample is preferred if there is clinical suspicion of multiple sclerosis (MS). About 80% of patients with MS have elevated IgG antibody levels in their CSF, making this test useful for diagnosis [2]. This test should be interpreted in the context of pertinent clinical and family history and physical examination findings. References 1. Burtis C, et al. Tietz Fundamentals of Clinical Chemistry and Molecular Diagnostics. St Louis, Missouri: Elsevier; 2015:310-314. 2. National Institutes of Health. CSF immunoglobulins G (IgG) index. https://medlineplus.gov/lab-tests/csf-immunoglobulin-g-igg-index/. Last updated June 27, 2018. Accessed January 14, 2020.

Laboratory assay overview

Adjunct in aiding clinical diagnosis of multiple sclerosis

Laboratory assay overview

Adjunct in aiding clinical diagnosis of multiple sclerosis