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Test ID: CASF IgG/Albumin Ratio, Spinal Fluid

Reporting Name

IgG/Albumin Ratio, CSF

Useful For

Assessment of cerebrospinal fluid (CSF) IgG/albumin ratio in the absence of a paired CSF and serum specimen

Clinical Information

Elevation of IgG levels in the cerebrospinal fluid (CSF) of patients with inflammatory diseases of the central nervous system (CNS) (multiple sclerosis: MS, neurosyphilis, acute inflammatory polyradiculoneuropathy, subacute sclerosing panencephalitis) is due to local CNS synthesis of IgG.

 

The 2 most commonly used diagnostic laboratory tests for MS are CSF index and oligoclonal banding. The CSF index is the CSF IgG to CSF albumin ratio compared to the serum IgG to serum albumin ratio. The CSF index is therefore an indicator of the relative amount of CSF IgG compared to serum and any increase in the index is a reflection of IgG production in the central nervous system. The IgG synthesis rate is a mathematical manipulation of the CSF index data and can also be used as a marker for CNS inflammatory diseases.

Interpretation

Cerebrospinal fluid IgG index is positive (elevated) in approximately 80% of patients with multiple sclerosis.

 

Analytic Time

Same day/1 day

Day(s) and Time(s) Performed

Monday through Saturday; 2 p.m.

Clinical Reference

1. Tourtellotte WW, Walsh MJ, Baumhefner RW, et al: The current status of multiple sclerosis intra-blood-brain-barrier IgG synthesis. Ann NY Acad Sci 1984;436:52-67

2. Bloomer LC, Bray PF: Relative value of three laboratory methods in the diagnosis of multiple sclerosis. Clin Chem 1981;27(12):2011-2013

3. Hische EA, van der Helm HJ: Rate of synthesis of IgG within the blood-brain barrier and the IgG index compared in the diagnosis of multiple sclerosis. Clin Chem 1987;33(1):113-114

4. Swanson JW: Multiple Sclerosis: Update in diagnosis and review of prognastic factors. Mayo Clin Proc 1989;64:577-586

5. Markowitz H, Kokmen E: Neurologic diseases and the cerebrospinal fluid immunoglobulin profile. Mayo Clin Proc 1983;58:273-274

Method Name

Nephelometry

Specimen Type

CSF


Advisory Information


The cerebrospinal fluid (CSF) index in which the CSF IgG/albumin ratio is compared to the serum IgG/albumin ratio aids in the diagnosis of individuals with multiple sclerosis. See SFIN / Cerebrospinal Fluid (CSF) IgG Index, Serum and Spinal Fluid.



Specimen Required


Collection Container/Tube: Sterile vial

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL


Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
CSF Refrigerated (preferred) 14 days
  Ambient  14 days
  Frozen  14 days

Reference Values

CSF IgG: 0.0-8.1 mg/dL

CSF albumin: 0.0-27.0 mg/dL

CSF IgG/albumin: 0.00-0.21

Test Classification

This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

82042

82784

LOINC Code Information

Test ID Test Order Name Order LOINC Value
CASF IgG/Albumin Ratio, CSF 2470-3

 

Result ID Test Result Name Result LOINC Value
IGG_C IgG, CSF 2464-6
ALB_C Albumin, CSF 1746-7
AIGAC IgG/Albumin, CSF 2470-3
Mayo Clinic Laboratories | Neurology Catalog Additional Information:

mml-Neuroimmunology, mml-Neuro-ophthalmology