IgG and albumin quantitation in both serum and spinal fluid samples and the calculation of IgG synthesis rate in the central nervous system
3 - 6 days
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
Serum and cerebrospinal fluid (CSF)
1.5 mL serum and 1 mL CSF
0.7 mL serum and 0.5 mL CSF
Red-top tube or gel-barrier tube and sterile (CSF) container
Blood in CSF; failure to obtain blood and CSF specimens
Evaluate the de novo rate of synthesis of IgG in CNS; diagnose inflammatory and autoimmune diseases involving CNS, in particular, multiple sclerosis; determine if IgG synthesis rate is based on the quotient of average normal serum IgG/average normal CSF IgG
CSF IgG, CSF albumin, and serum IgG: immunologic; serum albumin: spectrophotometry; synthesis rate by calculation
Synthesis rate: -9.9 to +3.3 mg/24 hours
Tourtellotte IgG synthesis rate is theoretically the most definitive approach to determining IgG production by the central nervous system. It is based upon an empirically-derived formula, the validity of which, however, has been verified by radiolabeled IgG experiments.1 The synthesis rate formula involves a constant described as “a ratio constant that quantitatively determines the proportion of CSF IgG that normally passes by filtration from the serum into the CSF across an intact BBB” (blood brain barrier). The formula is given as:
de novo CNS IgGsyn = ((IgGcsf - IgGs/369) - (Albcsf - Albs/230) (IgGs / Albs) (0.43)) x 5
A study by Tourtellotte and associates has shown that about 90% of multiple sclerosis patients show evidence of enhanced IgG synthesis.2 A study from the Cleveland Clinic indicates a sensitivity and specificity comparable to that for the IgG index in predictive value for MS.3 Sensitivity (96%) and specificity (98%) applied to a group considered as definite multiple sclerosis. A group of “possible multiple sclerosis” patients included a number of cases in which CNS IgG synthesis was normal − just 55% had an elevated rate. In the group with “neurologic diseases other than MS,” 96% of patients had normal CNS IgG synthesis. The study suggests that determination of CSF IgG synthesis rate contributes importantly to the diagnosis of MS. The study also emphasizes that correlations between test results and diagnoses are dependent upon the validity of what must remain a clinical neurologic diagnosis.
|Order Code||Order Code Name||Order Loinc||Result Code||Result Code Name||UofM||Result LOINC|
|085928||Immunoglobulin G,Syn Rate,CSF||012212||IgG, Quant, CSF||mg/dL||2464-6|
|085928||Immunoglobulin G,Syn Rate,CSF||012230||Albumin, CSF||mg/dL||1746-7|
|085928||Immunoglobulin G,Syn Rate,CSF||001081||Albumin||g/dL||1751-7|
|085928||Immunoglobulin G,Syn Rate,CSF||001776||Immunoglobulin G, Qn, Serum||mg/dL||2465-3|
|085928||Immunoglobulin G,Syn Rate,CSF||085937||IgG, Syn Rate,CSF||mg/day||14116-8|
© 2021 Laboratory Corporation of America® Holdings and Lexi-Comp Inc. All Rights Reserved.
CPT Statement/Profile Statement
The LOINC® codes are copyright © 1994-2021, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee. Permission is granted in perpetuity, without payment of license fees or royalties, to use, copy, or distribute the LOINC® codes for any commercial or non-commercial purpose, subject to the terms under the license agreement found at https://loinc.org/license/. Additional information regarding LOINC® codes can be found at LOINC.org, including the LOINC Manual, which can be downloaded at LOINC.org/downloads/files/LOINCManual.pdf