Agarose gel electrophoresis of concentrated CSF is used to detect oligoclonal bands, defined as two or more discrete bands in the gamma region that are absent or of less intensity than in the concurrently tested patient’s serum.

Fractionation (i.e., electrophoresis) of CSF is used to evaluate bacterial and viral infections and tumors of the CNS. However, the most important application of CSF protein electrophoresis is the detection and diagnosis of MS. Abnormalities of CSF in MS include an increase in total protein, primarily from IgG, which is the main component of the gamma-globulin fraction. Abnormal immunoglobulins migrate as discrete, sharp bands, called oligoclonal bands. This is the pattern observed in MS: a pattern of discrete bands within the gamma-globulin portion of the electrophoretic pattern. However, oligoclonal bands are found in the CSF of patients with other types of nervous system disorders of the immune system, including HIV.

Electrophoresis is also the method of choice to determine whether a fluid is actually CSF. Identification can be made based on the appearance of an extra band of transferrin (referred to as TAV), which occurs in CSF and not in serum.

Globulins:

• Oligoclonal banding: none present

• Alpha₁-globulin: 2%–7% (0.02–0.07)

• Alpha₂-globulin: 4%–12% (0.04–0.12)

• Beta-globulin: 8%–18% (0.08–0.18)

• Gamma-globulin: 3%–12% (0.03–0.12)

• Prealbumin: 2%–7% (0.02–0.07)

• Albumin: 56%–76% (0.56–0.76)

• IgA: 0.10 mg/dL or 1.0 mg/L

• IgD: 3.0 U/mL or 3.0 kU/L

• IgG: 5.0 mg/dL or 50 mg/L

• IgG synthesis rate: 0.0–8.0 mg/24 hr (average is 3.0) or 0.0–8.0 mg/d

• IgG-to-albumin ratio: 0.09–0.25

• IgM: 0.017 mg/dL or 0.17 mg/L

1. A lumbar puncture is performed (see Lumbar Puncture [Spinal Tap]).

2. Obtain 3 mL of CSF for this test in a sterile screw-top tube. The sample must be frozen if the test is not performed immediately.

3. Apply a sample of the concentrate to a thin-layer agarose gel. Subject the agarose gel to electrophoresis. CSF is concentrated approximately 80-fold by selective permeability. Serum electrophoresis must be done concurrently for interpretation of the bands.

1. Increases in CSF IgG or in the IgG-to-albumin index occur in the following conditions:

   1. MS

   2. SSPE

   3. Tumors of the brain and meninges

   4. Chronic CNS infections

   5. Some patients with meningitis, Guillain-Barré syndrome, lupus erythematosus involving the CNS, and other neurologic conditions

2. Increases in the CSF albumin index occur in the following conditions:

   1. Obstruction of CSF circulation

   2. Damage to the CNS blood–brain barrier

   3. Diabetes

   4. Systemic lupus erythematosus of the CNS

   5. Guillain-Barré syndrome

   6. Polyneuropathy

   7. Cervical spondylosis

3. Increased CSF gamma-globulin and the presence of oligoclonal bands occur in the following conditions:

   1. MS

   2. Neurosyphilis

   3. SSPE

   4. Stroke

   5. Viral and bacterial meningitis

   6. Progressive rubella panencephalitis

   7. Cryptococcal meningitis

   8. Idiopathic polyneuritis

   9. Burkitt lymphoma

   10. HIV-1 (AIDS)

   11. Guillain-Barré syndrome

4. Increased CSF synthesis of IgG occurs in the following conditions:

   1. MS (90% of definite cases)

   2. Inflammatory neurologic diseases

   3. Post-polio syndrome

Pretest Patient Care

1. Follow pretest patient care for lumbar puncture (see Lumbar Puncture [Spinal Tap]).

2. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

1. A traumatic tap invalidates the results.

2. Recent myelography affects the results.