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HelpTest ID: CASF IgG/Albumin Ratio, Spinal Fluid
Reporting Name
IgG/Albumin Ratio, CSFUseful 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 (intrathecal) 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 CNS. 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.
Report Available
1 to 3 daysDay(s) Performed
Monday through Friday
Clinical Reference
1. Tourtellotte WW, Walsh MJ, Baumhefner RW, Staugaitis SM, Shapshak P. 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 prognostic factors. Mayo Clin Proc. 1989;64(5):577-586
5. Markowitz H, Kokmen E. Neurologic diseases and the cerebrospinal fluid immunoglobulin profile. Mayo Clin Proc. 1983;58(4):273-274
6. Thompson AJ, Banwell BL, Barkhof F, et al. Diagnosis of multiple sclerosis: 2017 revisions of the McDonald criteria. Lancet Neurol. 2018;17(2):162-73. doi:10.1016/S1474-4422(17)30470-2
7. Gurtner KM, Shosha E, Bryant SC, et al. CSF free light chain identification of demyelinating disease: comparison with oligoclonal banding and other CSF indexes. Clin Chem Lab Med. 2018;56(7):1071-1080. doi:10.1515/cclm-2017-0901
8. Rifai N, Horvath AR, Wittwer CT, eds: Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018
Method Name
Nephelometry
Specimen Type
CSFOrdering Guidance
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 SFIG / Cerebrospinal Fluid IgG Index Profile, Serum and Spinal Fluid.
Specimen Required
Specimen Type: Spinal fluid (CSF)
Container/Tube: Sterile vial
Specimen Volume: 1 mL
Collection Instructions:
1. Submit CSF from collection vial number 2 (preferred, not required).
2. Label specimen as CSF.
Specimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| CSF | Refrigerated (preferred) | 28 days |
| Frozen | 28 days | |
| Ambient | 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, approved, or is exempt by the US 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 |
mml-Neuroimmunology, mml-Neuro-ophthalmology