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Test Code SFINC Cerebrospinal Fluid (CSF) IgG Index, Spinal Fluid


Specimen Required


Only orderable as part of a profile. For more information see SFIG / Cerebrospinal Fluid (CSF) IgG Index Profile, Serum and Spinal Fluid.

 

Specimen Type: Spinal fluid

Container/Tube: Sterile vial

Specimen Volume: 1 mL

Collection Instructions: Label specimen as spinal fluid.


Useful For

Aiding in the diagnosis of multiple sclerosis and other central nervous system inflammatory conditions

Method Name

Only orderable as part of a profile. For more information see SFIG / Cerebrospinal Fluid (CSF) IgG Index Profile, Serum and Spinal Fluid.

 

Nephelometry

Reporting Name

IgG Index, CSF

Specimen Type

CSF

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
CSF Refrigerated (preferred) 28 days
  Frozen  28 days
  Ambient  14 days

Reject Due To

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Clinical Information

Elevation of IgG in the cerebrospinal fluid (CSF) of patients with inflammatory diseases of the central nervous system (CNS) such as multiple sclerosis (MS), neurosyphilis, acute inflammatory polyradiculoneuropathy, subacute sclerosing panencephalitis may be  due to local (intrathecal) synthesis of IgG. Elevations of CSF IgG or the CSF/serum IgG ratio may also occur as a result of permeability of the blood brain barrier, and hence, a correction using albumin measurements in CSF and serum is appropriate.

 

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. 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. The test is commonly ordered with oligoclonal banding or immunoglobulin kappa free light chains in CSF to aid in the diagnosis of demyelinating conditions.

Reference Values

Only orderable as part of a profile. For more information see SFIG / Cerebrospinal Fluid (CSF) IgG Index Profile, Serum and Spinal Fluid.

 

CSF index: 0.00-0.85

CSF IgG: 0.0-8.1 mg/dL

CSF albumin: 0.0-27.0 mg/dL

CSF IgG/albumin: 0.00-0.21

CSF IgG synthesis rate: 0-12 mg/24 hours

Interpretation

Cerebrospinal fluid (CSF) IgG synthesis rate indicates the rate of increase in the daily CSF production of IgG in milligrams per day.

 

A result greater than 12 mg/24 hours is elevated.

 

A CSF index greater than 0.85 is elevated and indicative of increased synthesis of IgG.

Cautions

The cerebrospinal fluid index can be elevated in other inflammatory demyelinating diseases such as neurosyphilis, acute inflammatory polyradiculoneuropathy, and subacute sclerosing panencephalitis.

Method Description

Cerebrospinal fluid (CSF) and serum IgG and CSF albumin are determined by immunonephelometry. The CSF IgG index and synthesis rate are calculated and reported. Albumin in serum is determined by turbidimetry (bromocresol green method). The serum IgG and albumin, CSF IgG and albumin, and serum and CSF IgG/albumin ratios are reported.(Instruction manual: Siemens Nephelometer II Operations. Siemens, Inc; Version 2.3, 2008; Addendum to the Instruction Manual 2.3, 08/2017)

Day(s) Performed

Monday through Friday

Report Available

Same day/1 to 2 days

Specimen Retention Time

2 weeks

Performing Laboratory

Mayo Clinic Laboratories in Rochester

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

Result ID Test Result Name Result LOINC Value
INDEX IgG Index, CSF 14117-6
IGG_C IgG, CSF 2464-6
ALB_C Albumin, CSF 1746-7
AIGAC IgG/Albumin, CSF 2470-3
SRATE Synthesis Rate, CSF 14116-8