Home
HelpTest ID SFIG Cerebrospinal Fluid IgG Index Profile, Serum and Spinal Fluid
Specimen Required
Both serum and spinal fluid are required.
-Spinal fluid must be obtained within 7 days of serum collection.
-Two individual serum samples are required.
Collection Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Submission Container/Tube: 2 Plastic vials
Specimen Volume: 2 mL in 2 plastic vials, each vial containing 1 mL
Collection Instructions: Within 2 hours of collection, centrifuge and aliquot serum into 2 plastic vials.
Specimen Type: Spinal fluid
Container/Tube: Sterile vial
Preferred: Collection vial number 2
Specimen Volume: 1 mL
Collection Instructions: Label specimen as SFINC.
Useful For
Aiding in the diagnosis of multiple sclerosis and other central nervous system inflammatory conditions
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| SFINC | IgG Index, CSF | No | Yes |
| SFIGS | IgG, S | No | Yes |
| ALBS1 | Albumin, S | Yes, (order ALB) | Yes |
Method Name
SFINC, SFIGS: Nephelometry
ALBS1: Photometric
Reporting Name
CSF IgG Index ProfileSpecimen Type
CSFSerum
Specimen Minimum Volume
Serum: 1 mL in 2 plastic vials, each vial containing 0.5 mL; Spinal fluid: 0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| CSF | Refrigerated (preferred) | 28 days | |
| Frozen | 28 days | ||
| Ambient | 14 days | ||
| Serum | Refrigerated (preferred) | 14 days | |
| Frozen | 28 days | ||
| Ambient | 7 days |
Reject Due To
| Criteria apply to serum specimens only. For CSF specimens, the criteria are not applicable. | |
| Gross hemolysis | Reject |
| Gross lipemia | Reject |
| Gross icterus | OK |
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, neurosyphilis, acute inflammatory polyradiculoneuropathy, and subacute sclerosing panencephalitis may be due to local (intrathecal) synthesis of IgG.
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 reflects 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
CSF index: 0.00-0.70
CSF IgG: 0.0-8.1 mg/dL
CSF albumin: 0.0-27.0 mg/dL
Serum IgG
0-4 months: 100-334 mg/dL
5-8 months: 164-588 mg/dL
9-14 months: 246-904 mg/dL
15-23 months: 313-1,170 mg/dL
2-3 years: 295-1,156 mg/dL
4-6 years: 386-1,470 mg/dL
7-9 years: 462-1,682 mg/dL
10-12 years: 503-1,719 mg/dL
13-15 years: 509-1,580 mg/dL
16-17 years: 487-1,327 mg/dL
≥18 years: 767-1,590 mg/dL
Serum albumin
≥12 months: 3,500-5,000 mg/dL
Reference values have not been established for patients who are younger than 12 months.
CSF IgG/albumin: 0.00-0.21
Serum IgG/albumin: 0.0-0.4
CSF IgG synthesis rate: 0-12 mg/24 h
Albumin quotient: <14
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 h is elevated.
A CSF IgG index greater than 0.70 is elevated and indicative of increased synthesis of IgG.
Cautions
The cerebrospinal fluid IgG index can be elevated in other inflammatory demyelinating diseases, such as neurosyphilis, acute inflammatory polyradiculoneuropathy, and subacute sclerosing panencephalitis.
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 Dec;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 Jan;33(1):113-114
4. Thompson AJ, Banwell BL, Barkhof F, et al: Diagnosis of multiple sclerosis: 2017 revisions of the McDonald criteria. Lancet Neurol. 2018 Feb;17(2):162-73. doi:10.1016/S1474-4422(17)30470-2
5. 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 Jun 27;56(7):1071-1080. doi:10.1515/cclm-2017-0901
6. Rifai N, Chiu, RWK, Burnham, CD, Wittwer CT, eds. Tietz Textbook of Laboratory Medicine. 7th ed. Elsevier; 2023
7. Saadeh RS, Ramos PA, Algeciras-Schimnich A, Flanagan EP, Pittock SJ, Willrich MA. An update on laboratory-based diagnostic biomarkers for multiple sclerosis and beyond. Clin Chem. 2022;68(9):1134-1150
Method Description
CSF IgG and albumin, and Serum IgG:
The cerebrospinal fluid (CSF) IgG, CSF albumin, and serum IgG are determined by immunonephelometry. The CSF IgG index and synthesis rate are calculated and reported.(Instruction manual: Siemens BN II Nephelometer Operations. Siemens, Inc.; Version 2.3, 2008; Addendum to the Instruction Manual 2.4, 07/2019)
Serum albumin is measured by colorimetry. The dye, bromocresol green (BCG), is added to serum in an acid buffer. The color intensity of the blue-green albumin-BCG complex is directly proportional to the albumin concentration and is determined photometrically.(Package insert: ALB2. Roche Diagnostics; V 8.0, 06/2024)
Day(s) Performed
Monday through Friday
Report Available
2 to 5 daysTest 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
82040
82042
82784 x 2