CSF Oligoclonal Band Interpreter
CSF Oligoclonal Band Interpreter
Isoelectric focusing of paired cerebrospinal fluid and serum gives five patterns, and only two of them mean intrathecal synthesis. Without the serum track there is no answer at all — bands present in both compartments came from the blood. This page reads the pattern and says what the 2024 McDonald criteria now do with it.
CSF oligoclonal band pattern
IEF pattern → interpretationType 2 pattern, 6 CSF-restricted bands, MRI dissemination in space demonstrated, kappa index not measured
The five patterns
Type 1 — no bands in either. Type 2 — bands in CSF only. Type 3 — bands in CSF plus identical bands in both. Type 4 — identical bands in both only. Type 5 — monoclonal band in both.
- the paired serum
- mandatory, run simultaneously in an adjacent track. Bands present in both compartments were made outside the central nervous system and transferred passively, which is the distinction the whole test exists to make
- types 2 and 3
- the positive patterns. Both contain bands restricted to the fluid, and both are described in multiple sclerosis
- types 4 and 5
- negative for intrathecal synthesis. Type 4 is a systemic oligoclonal response; type 5 is a paraproteinaemia and needs its own investigation
- two or more bands
- the conventional threshold for a positive report. A single restricted band is equivocal
- sensitivity
- in excess of 95% for multiple sclerosis by isoelectric focusing with immunoblotting, against roughly 60% for a raised IgG index on the same patients
- specificity
- about 94% against healthy controls but about 61% against other inflammatory neurological disease — the figure that actually applies in a neurology clinic
Worked example
Type 2 pattern, 6 CSF-restricted bands, MRI dissemination in space demonstrated, kappa index not measured
A paired serum was run, so the pattern can be read
Six bands in the CSF track, none of them matched in the serum track
Six is well above the threshold of two, so this is unequivocally positive
Immunoglobulin restricted to the fluid can only have been made inside the central nervous system
With dissemination in space on MRI, the 2024 McDonald criteria allow this to substitute for dissemination in time
So multiple sclerosis can be diagnosed now rather than after a second attack — provided the differential has been excluded clinically, because bands are not specific to multiple sclerosis
The five consensus patterns
| Type | CSF track | Serum track | Means | Positive for intrathecal synthesis? |
|---|---|---|---|---|
| 1 | No bands | No bands | No detectable intrathecal or systemic oligoclonal response | No |
| 2 | Two or more bands | No bands | Intrathecal IgG synthesis — the classic multiple sclerosis pattern | Yes |
| 3 | Bands present, some matched in serum and some not | Some of the same bands | Intrathecal synthesis and a systemic response. Also seen in multiple sclerosis | Yes |
| 4 | Bands present, all matched in serum | Identical bands | A systemic oligoclonal response, transferred passively into the fluid. The mirror pattern | No |
| 5 | Monoclonal band | Identical monoclonal band | A paraprotein crossing from blood — investigate for a plasma cell dyscrasia | No |
What the 2024 McDonald criteria do with a positive CSF
| Element | 2017 criteria | 2024 revisions |
|---|---|---|
| Evidence of intrathecal synthesis | CSF-specific oligoclonal bands | Oligoclonal bands or a raised kappa free light chain index, treated as equivalent |
| Kappa free light chain cut-off | Not part of the criteria | Accepted without a single mandated numerical cut-off — the laboratory's own applies |
| Role of CSF positivity | Could substitute for dissemination in time | Substitutes for dissemination in time, which is no longer mandatory for diagnosis |
| Anatomical topographies | Four — periventricular, juxtacortical, infratentorial, spinal cord | Five — the optic nerve is added |
| Supporting MRI biomarkers | Not included | Central vein sign and paramagnetic rim lesions may be used to improve specificity |
Other causes of CSF-specific oligoclonal bands
| Group | Examples |
|---|---|
| Infection | Neurosyphilis, Lyme neuroborreliosis, HIV, neurotuberculosis, herpes encephalitis, subacute sclerosing panencephalitis, neurocysticercosis |
| Autoimmune and inflammatory | Systemic lupus erythematosus, Sjögren syndrome, Behçet disease, neurosarcoidosis, CNS vasculitis, autoimmune encephalitis including anti-NMDA receptor encephalitis |
| Other demyelinating disease | Acute disseminated encephalomyelitis, acute myelitis, neuromyelitis optica spectrum disorder (usually negative, but not always) |
| Neoplastic and paraneoplastic | Central nervous system lymphoma, paraneoplastic neurological syndromes |
| Peripheral nervous system | Guillain–Barré syndrome |
Why the serum track is the test
Isoelectric focusing separates immunoglobulin by isoelectric point, and an oligoclonal response — a handful of plasma cell clones each making one antibody — shows up as discrete bands rather than a smear. Followed by IgG immunoblotting, it is the most sensitive test available for intrathecal immunoglobulin synthesis: sensitivity in excess of 95% for multiple sclerosis across roughly three thousand patients, against about 60% for a raised IgG index on the same samples. That gap is the reason the quotient calculators on this site all point here.
The whole test, though, rests on something that is easy to skip. Immunoglobulin made anywhere in the body crosses into cerebrospinal fluid, more of it when the barrier is disturbed, and it arrives with its clonality intact. A patient with chronic hepatitis, systemic lupus or HIV can therefore have a cerebrospinal fluid gel covered in bands and no intrathecal synthesis whatever. The only way to tell is to run the patient's serum in an adjacent track of the same gel, at the same time, and ask which bands are restricted to the fluid. Freedman's consensus statement requires exactly that, and it is not a counsel of perfection: a CSF gel reported without a serum track is uninterpretable, and the two patterns it will be over-called as — type 4, identical bands in both, and type 5, a monoclonal band in both — are respectively a systemic immune response and a paraprotein. Neither supports a diagnosis of multiple sclerosis and the second needs a myeloma screen. The paired serum should be drawn at the lumbar puncture; a sample taken more than two or three weeks later no longer represents the blood the fluid was in contact with, because serum IgG turns over with a half-life of about 23 days.
Given a proper pair, five patterns are described and only two of them are positive. Type 2 is bands in the fluid and none in serum, the classic result. Type 3 is bands in the fluid plus identical bands in both compartments — intrathecal synthesis with a systemic response alongside it, equally positive and equally compatible with multiple sclerosis, with the shared bands worth investigating separately. Type 1 is a clean gel. Two or more restricted bands is the conventional threshold for calling a result positive, and a single band is genuinely equivocal rather than weakly positive; it should be reported as such.
What has changed recently is not the gel but what a positive gel entitles you to conclude. The 2024 revisions of the McDonald criteria, published by Montalban and colleagues in 2025, supersede the 2017 version. Three changes matter to a laboratory. Dissemination in time is no longer mandatory: where dissemination in space is demonstrated and the cerebrospinal fluid is positive, the diagnosis can be made at first presentation. The optic nerve becomes a fifth anatomical topography. And the kappa free light chain index is accepted as equivalent to oligoclonal bands for demonstrating intrathecal synthesis — a quantitative, automatable test now carries the same diagnostic weight as a reader-dependent gel, without the criteria mandating a single numerical cut-off, so the laboratory's own applies. None of which makes the test specific. Bands occur in neurosyphilis, neuroborreliosis, autoimmune encephalitis, lupus, neurosarcoidosis, central nervous system lymphoma and a dozen other things, and the specificity of bands for multiple sclerosis falls from about 94% against healthy controls to about 61% against other inflammatory neurological disease. That second figure is the one a neurology clinic operates under.
Frequently asked questions
Why is a paired serum sample needed for oligoclonal bands?
Because oligoclonal immunoglobulin made anywhere in the body crosses into cerebrospinal fluid and appears on the gel. Only bands present in the fluid and absent from a simultaneously run serum track can have been made inside the central nervous system. A CSF gel without its serum cannot distinguish the two and should not be reported as positive or negative.
What do the five isoelectric focusing patterns mean?
Type 1, no bands in either — negative. Type 2, bands in CSF only — intrathecal synthesis, the classic multiple sclerosis pattern. Type 3, CSF bands plus identical bands in both — intrathecal synthesis with a systemic response, also positive. Type 4, identical bands in both — systemic, not intrathecal. Type 5, a monoclonal band in both — a paraprotein needing its own investigation.
How many bands count as positive?
Two or more bands restricted to the cerebrospinal fluid is the conventional threshold. A single restricted band is equivocal: some patients with one band develop multiple sclerosis and many do not, and inter-gel and inter-reader variation is real at that level. Report one band as equivocal and consider a kappa free light chain index, which is quantitative.
What do the 2024 McDonald criteria say about oligoclonal bands?
CSF positivity can substitute for dissemination in time, which the 2024 revisions no longer make mandatory — so with dissemination in space on MRI, a positive CSF can complete the diagnosis at first presentation. The 2024 criteria also accept a raised kappa free light chain index as equivalent to oligoclonal bands, without specifying a single numerical cut-off. They supersede the 2017 criteria.
Are oligoclonal bands specific to multiple sclerosis?
No. They are described in neurosyphilis, Lyme neuroborreliosis, HIV, neurotuberculosis, subacute sclerosing panencephalitis, systemic lupus, Sjögren syndrome, Behçet disease, neurosarcoidosis, CNS vasculitis, autoimmune encephalitis, central nervous system lymphoma, paraneoplastic disease and Guillain–Barré syndrome. Against inflammatory disease controls rather than healthy ones, specificity for multiple sclerosis falls from about 94% to about 61%.
Can oligoclonal bands be negative in multiple sclerosis?
Yes, in a small minority. Sensitivity by isoelectric focusing with immunoblotting exceeds 95%, so a negative gel makes the diagnosis less likely without excluding it. Check that the method was isoelectric focusing with IgG immunoblotting rather than a less sensitive electrophoretic technique, and consider a kappa free light chain index, which is occasionally positive when the gel is not.
Related calculators
References
- Andersson M, Alvarez-Cermeño J, Bernardi G, et al. Cerebrospinal fluid in the diagnosis of multiple sclerosis: a consensus report. J Neurol Neurosurg Psychiatry. 1994;57(8):897–902.
- Freedman MS, Thompson EJ, Deisenhammer F, et al. Recommended standard of cerebrospinal fluid analysis in the diagnosis of multiple sclerosis: a consensus statement. Arch Neurol. 2005;62(6):865–870.
- Montalban X, Lebrun-Frénay C, Oh J, et al. Diagnosis of multiple sclerosis: 2024 revisions of the McDonald criteria. Lancet Neurol. 2025;24(10):850–865.
- Deisenhammer F, Zetterberg H, Fitzner B, Zettl UK. The cerebrospinal fluid in multiple sclerosis. Front Immunol. 2019;10:726.
- Jin H, Lu Q, Gao F, Hao H. Application of oligoclonal bands and other cerebrospinal fluid variables in multiple sclerosis and other neuroimmunological diseases: a narrative review. Ann Transl Med. 2023;11(7):282.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.