IgG Index, CSF + Serum

Test Overview

Method

Various

Analytical Platform

Serum: Beckman Coulter AU680; CSF: Cobas C6000

Method Description

IgG Index:(CSF IgG/Serum IgG) X (Serum albumin/CSF Albumin) X 100
Serum Albumin – Beckman Coulter AU680
PRINCIPLE: At pH 4.2, albumin from the sample combines with BCG reagent to form an intense green complex. The change in absorbance of the albumin-BCG complex is measured bichromatically (600/800 nm). This change in absorbance is directly proportional to the concentration of albumin in the sample.
Serum IgG – Beckman Coulter AU680
PRINCIPLE: Immune complexes formed in solution scatter light in proportion to their size, shape and concentration. Turbidimeters measure the reduction of incident light due to reflection, absorption or scatter.
In the procedure, the decreases in intensity of light transmitted (increase in absorbance) through particles suspended in solution is the result of complexes formed during the antigen-antibody reaction.
CSF Albumin – Cobas C6000
PRINCIPLE: The quantitative determination of Albumin in CSF is based on an immunoturbidimetric assay.
Anti-albumin antibodies react with the antigen in the sample to form antigen/antibody complexes which, following agglutination, are measured turbidimetrically.
CSF IgG – Cobas C6000
PRINCIPLE: The quantitative determination of IgG in CSF is based on an immunoturbidimetric assay.
Anti-IgG antibodies react with antigen in the sample to form an antigen-antibody complex. Following agglutination, this is measured turbidmetrically. Addition of polyethylene glycol allows the reaction to progress rapidly to the end point, increases sensitivity, and reduces the risk of samples containing excess antigen producing false negative results.

Result Included

IgG, CSF; Albumin, CSF; IgG Index; Serum IgG; Serum Albumin

Specimen

Specimen Type

CSF & Serum

Volume

Sample Volume

CSF: 0.5mL; Serum: 0.5 mL

Collection & Handling

Handling Information

Store and send frozen – specimen must be received at ICL within 5 days of collection.

Rejection Criteria

Criteria	Specification
Specimen	Plasma

Performance & Interpretation

Turnaround Time

10 days

Results

IgG, CSF

g/L

<0.060
Albumin, CSF

g/L

0.100 - 0.250
IgG Index

<70

Comment

IgG Index = (CSF IgG/Serum IgG) X (Serum albumin/CSF Albumin) X 100
Serum IgG

g/L

6.35-17.41
Serum Albumin

g/L

35.00-50.00

Referral Location

Canada

Interface & Setup

HL7 Interface Codes

Order Code	Result Name	Result Codes	Units
IGI CS	IgG, CSF	3060	g/L
	Albumin, CSF	3061
	IgG Index	36612
	Serum IgG	63563	g/L
	Serum Albumin	63564	g/L

Test Version

Last Updated

2025-07-16