LP64090-1

IgG index

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Descriptions

The relative CSF/serum quotient (CSQrel, synonymous with antibody specificity index (ASI) or IgG index) is calculated to determine intrathecal antibody synthesis for diagnosis of central nervous system (CNS) infections. The antibody (Ab) concentration in the patient's CSF divided by the Ab concentration in the patient's serum equals the pathogen specific CSF/Serum quotient (CSQpath-spec). If the patient's CSQpath-spec is greater than the CSQtotal (CSF/Serum quotient of the whole IgG), then an intrathecal synthesis of specific antibodies (IgG) is present. It has proven to be the most sensitive inflammation parameter in CSF analysis to date and is more sensitive than the Western blot, the "oligoclonal" response, and the empirical differentiation of CSF immunoglobulins. In multiple sclerosis (MS), increased CSQrel is a common finding, but above normal IgG indicies are found in several other diseases (e.g. TBE, CMV, and meningitis). Source: NCBI PubMed , PMID 1318123

CSF IgM, IgA, and IgG indexes are indicators of intrathecal immunoglobulin synthesis. The calculations incorporate the CSF-serum albumin quotient, an indicator of blood-brain-barrier (BBB) function, in order to differentiate whether the immunoglobulins found in the CSF were produced intrathecally or leaked across the BBB. These immunoglobulin indexes can be useful in the diagnosis of central nervous system infections, neoplasms and primary neurologic diseases such as multiple sclerosis. They also have the potential to monitor treatment efficacy in conditions such as systemic lupus erythematosus with CNS involvement, in which one study found that all three indexes decreased significantly along with CNS symptoms during successful treatment. The CSF IgM index is calculated as (CSF IgM/serum IgM)/(CSF albumin/serum albumin), which can also be represented as (CSF IgM x serum albumin)/(serum IgM x CSF albumin). PMID: 3899036 Source: Regenstrief LOINC , PMID: 3899036

Basic Part Properties

Part Name

IgG index

Part Display Name

IgG index

Part Type

Component (Describes the core component or analyte measured)

Created On

2007-05-10

Construct for LOINC Short Name

IgG index

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