Both
CSF
and serum specimens are required
to detect intrathecal IgG production.
In order to minimise false positive tests, both
CSF
and serum should be collected on the same day
(though a gap between specimens of up to 5 days is accepted).
To minimise delay, on the lab request form we recommend to write:
"
CSF
IgG oligoclonal bands"
under the CSF section and
"Paired serum for
CSF
IgG oligoclonal band test"
at the
"Other tests" section
. Requests that do not satisfy sample requirements may be delayed.
Sample stability:
|
CSF IgG
|
CSF Albumin
|
Requires 3X plain microsample tubes.
CSF albumin : < 250 mg/L
CSF IgG : < 42 mg/L
Serum IgG : age dependent
Uncertainty of Measurement: CSF IgG 6%
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.
| Age Range | Either Sex |
|---|---|
| < 2 m | 25 - 40[1] |
| 2 m - 1 y | 32 - 45 |
| >= 1 y | 32 - 48 |
Serum Albumin
CSF protein analysis and oligoclonal bands: 10 working days
These tests are not available on weekends or after hours.
If expedited testing is required due to clinical needs, please contact the on-call chemical pathologist via LabLink or email ChemicalPathologist@adhb.govt.nz
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).
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 Samarina Musaad (Clinical Lead) : SamarinaM@adhb.govt.nz ext. 22402
Dr Cam Kyle: CampbellK@adhb.govt.nz ext 22052
Dr Weldon Chiu: WeldonC@adhb.govt.nz ext. 23427
Dr Campbell Heron: CHeron@adhb.govt.nz ext. 23427