Immunoglobulin G Index

CPT: 82040; 82042; 82784(x2)
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  • CSF IgG Index
  • CSF IgG:CSF Albumin Ratio
  • CSF IgG:CSF Total Protein Ratio
  • IgG Index, CSF
  • IgG Ratios and IgG Index, CSF

Test Includes

IgG and albumin quantitation in both serum and spinal fluid; CSF IgG:CSF albumin ratio; CSF IgG index

Special Instructions

The third tube of a routinely obtained three-tube set of CSF should be used for these studies.

Expected Turnaround Time

3 - 6 days

Related Documents

Specimen Requirements


Serum and cerebrospinal fluid (CSF)


1.5 mL serum and 1 mL CSF

Minimum Volume

0.7 mL serum and 0.5 mL CSF (Note: This volume does not allow for repeat testing.)


Red-top tube or gel-barrier tube and sterile (CSF) container

Storage Instructions

Room temperature

Stability Requirements



Room temperature

14 days


14 days


6 weeks

Freeze/thaw cycles

Stable x2

Test Details


Detect and measure the level of IgG production by the central nervous system; has been applied to the diagnosis of multiple sclerosis along with CSF IgG synthesis rate and CSF immunoglobulin “oligoclonal” bands


Conditions in which lymphoreticular elements of the CNS produce immunoglobulins will result in false-positive (in relation to multiple sclerosis) elevations. Such conditions include, but are not limited to, aseptic meningitis, lymphoma, neurosyphilis, Guillain-Barré syndrome, and cerebral lupus erythematosus. These conditions, however, are either uncommon or are not frequently associated with an increased IgG index.


CSF IgG, CSF albumin, and serum IgG: immunologic; serum albumin: spectrophotometry; ratio and index by calculation

Reference Interval

Index: 0.0−0.7

Additional Information

IgG index, synthesis rate, and oligoclonal bands have shown sensitivity at the 80% to 90% level but are not uniformly specific. CSF IgG may be increased, generally with inflammatory disorders of the CNS (eg, idiopathic polyneuropathy, neurosyphilis). Rents in the interface between blood and CSF will allow increase in CSF IgG. The three tests differentiate between increased barrier permeability and increased CNS immunoglobulin synthesis, each in a different manner. The ratio technique relates CSF IgG level to another protein that hopefully reflects protein present on the basis of increased blood/CSF permeability. CSF IgG/CSF total protein is such a measure. CSF IgG/CSF albumin has been proposed by Tourtellotte et al as equally discriminative for MS as the CSF IgG:CSF total protein ratio.1,2 The index provides good separation of increased CNS IgG production from protein increases, the result of altered permeability of blood/CNS interface.3

Hershey and Trotter have compared sensitivity/specificity (weighted equally) of these tests (not including IgG synthetic rate) and found the CSF IgG index superior with sensitivity of 91% and specificity of 96.5%. Gambino, however, has emphasized that these results are with cerebral infections and immunologic diseases eliminated so that considerable clinical judgment must be exercised. Results of IgG index testing appear to correlate with those of oligoclonal banding determinations, but the IgG index may have no specific value independent of the presence of oligoclonal bands.


1. Tourtellotte WW, Potvin AR, Fleming JO, et al. Multiple sclerosis: Measurement and validation of central nervous system IgG synthesis rate. Neurology. 1980 Mar; 30(3):240-244. 7189023
2. Tourtellotte WW, Staugaitis SM, Walsh MJ, et al. The basis of intra-blood-brain-barrier IgG synthesis. Ann Neurol. 1985 Jan; 17(1):21-27. 3985581
3. Valenzuela R, Mandler R, Goren H. Immunonephelometric quantitation of central nervous system IgG daily synthesis in multiple sclerosis. Clinical evaluation using predictive value theory. Am J Clin Pathol. 1982 Jul; 78(1):22-28. 7102604


Gambino R. CSF immunoglobulins. Lab Report for Physicians. 1981; 3:42-44.
Giles PD, Heath JP, Wroe SJ. Oligoclonal bands and the IgG index in multiple sclerosis: Uses and limitations. Ann Clin Biochem. 1989 Jul; 26(Pt 4):317-323. 2764482
Hershey LA, Trotter JL. The use and abuse of the cerebrospinal fluid IgG profile in the adult: A practical evaluation. Ann Neurol. 1980 Oct; 8(4):426-434. 6776879
Tourtellotte WW, Tavolato B, Parker JA, Comiso P. Cerebrospinal fluid electroimmunodiffusion. An easy, rapid, sensitive, reliable, and valid method for the simultaneous determination of immunoglobulin-G and albumin. Arch Neurol. 1971 Oct; 25(4):345-350. 4999856


Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
002238 Immunoglobulin G Index 012212 IgG, Quant, CSF mg/dL 2464-6
002238 Immunoglobulin G Index 012230 Albumin, CSF mg/dL 1746-7
002238 Immunoglobulin G Index 001776 Immunoglobulin G, Qn, Serum mg/dL 2465-3
002238 Immunoglobulin G Index 001081 Albumin g/dL 1751-7
002238 Immunoglobulin G Index 160311 IgG/Alb Ratio, CSF 2470-3
002238 Immunoglobulin G Index 101124 CSF IgG Index 14117-6

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