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CSF IgG index
Short Description : CSF protein analysis


CSF
Test performed by: LabPLUS VIM Proteins


Specimen Collection

Both CSF and serum specimens are required for detection of intrathecal production of IgG.

The CSF and serum samples should be collected on the same day.

CSF protein analysis should be requested on the form.

 

Sample stability:

CSF IgG

  • 1 day at 15-25 o C
  • 7 days at 2-8 o C  

CSF Albumin

  • 3 days at 2-8 o C  
  • 6 months at -20 o C  


Plain4 mL Plain Blood
SST3.5 mL SST Serum
MicrosamplePaediatric Microsample Serum

Requires 3X plain microsample tubes.


1 mL CSF
Reference Intervals

CSF albumin : < 250 mg/L 

CSF IgG : < 42 mg/L

Serum IgG : age dependent

Uncertainty of Measurement:    CSF IgG 10%

                                                           CSF Albumin 6% (>200 mg/L)


CSF/serum albumin index:   Normal < 9       

CSF/serum albumin index = CSF albumin (mg/L) / serum albumin (g/L)

This is an index of blood-brain barrier (BBB) integrity, adjusted for the serum albumin concentration. This index is increased in BBB dysfunction.

CSF IgG/albumin ratio:  Normal < 0.27

CSF IgG/albumin ratio = CSF IgG (mg/L) / CSF albumin (mg/L)

This is an index of local IgG production, adjusted for leakage of IgG from the plasma due to BBB dysfunction. (This ratio is used if a serum sample is not available.) This ratio is increased when local CNS IgG synthesis is occurring.

CSF IgG index:  Normal  < 0.7

CSF IgG index = (CSF IgG x serum albumin) / (CSF albumin x serum IgG)

This is the best  index of local IgG production, adjusted both for leakage of IgG due to BBB dysfunction and for serum albumin and IgG concentrations. This index is increased in more than 80% of cases of multiple sclerosis).  It is not specific for multiple sclerosis, and is increased in any condition where there is local CNS IgG synthesis.

NOTE:  All of the above parameters may be falsely elevated if the measurements were performed on a traumatic CSF tap.


Units: g/L
Age RangeEither Sex
< 2 m 25 - 40[1]
2 m - 1 y 32 - 45
>= 1 y 32 - 48

[1]

Serum Albumin


Turnaround Time:

CSF protein analysis and oligoclonal bands: 10 working days

These tests are not available on weekends or after hours.


Diagnostic Use and Interpretation

Confirmation of intrathecal IgG synthesis is used in investigating inflammatory diseases of the CNS.   IgG synthesis within the CNS is most commonly found in multiple sclerosis, but is also seen in other conditions including Guillane-Barre syndrome and neurosyphilis.

Intrathecal IgG synthesis is assessed by:

(a) measurement of CSF and serum IgG and albumin, and calculation of derived indices;

(b) detection of IgG oligoclonal bands by isoelectric focussing and immunofixation.

Oligoclonal bands is the more sensitive test, but takes longer to perform (up to 3 working days).

Both the above tests will be performed if CSF protein analysis is requested.

References

Tietz textbook of Clinical Chemistry, third edition.  (Formulae and reference ranges for CSF indices).


Contact Information

Emails to chemicalpathologist@adhb.govt.nz will receive priority attention from the on-call chemical pathologist.

If the query concerns a specific patient please include the NHI number in your email.

If email is not a suitable option, please contact the on-call chemical pathologist via Lablink (Auckland City Hospital ext. 22000 or 09-3078995).

Individual chemical pathologists may be contacted but will not be available at all times. 

After-hours : contact  Lablink (Auckland City Hospital ext. 22000 or 09-3078995) or hospital operator for on duty staff after hours.


Dr Cam Kyle (Clinical Head): CampbellK@adhb.govt.nz   ext 22052 

Dr Weldon Chiu: WeldonC@adhb.govt.nz   ext. 23427 

Dr Leah Ha: LHa@adhb.govt.nz  ext. 23427

Dr Samarina Musaad: SamarinaM@adhb.govt.nz ext. 22402 

Dr Leo Lam: ChiSingL@adhb.govt.nz  ext 22574



Last updated at 12:15:23 26/08/2021