CSF Immunoglobulin G (IgG) Index

Reviewed

Also called: Cerebrospinal fluid IgG level, Cerebrospinal fluid IgG measurement, CSF IgG level, IgG (Immunoglobulin G) spinal fluid, IgG synthesis rate

A CSF IgG index measures the level of immunoglobulin G (IgG) in your cerebrospinal fluid. It is used to help diagnose conditions affecting the central nervous system, especially multiple sclerosis (MS).

Specimen: Cerebrospinal fluid

Why this test may be ordered

  • To check for diseases of the central nervous system
  • To help diagnose multiple sclerosis (MS)
  • If you have symptoms such as blurred or double vision, tingling, numbness, pain, muscle spasms, weakness, dizziness, balance problems, bladder control issues, fatigue, or problems with thinking or memory

Preparation and collection

You don't need any special preparations, but you may be asked to empty your bladder and bowels before the test.

A spinal tap (lumbar puncture) is performed. You lie on your side or sit on an exam table. A provider cleans your back, injects anesthetic, and inserts a thin, hollow needle between two vertebrae in your lower spine to withdraw a small amount of cerebrospinal fluid. The procedure takes about five minutes.

There is very little risk to having a spinal tap. You may feel a pinch or pressure when the needle is inserted. After the test, you may have pain or tenderness at the site, some bleeding, or a headache that may last for several hours up to a week or more.

Understanding results

Your CSF IgG index results are interpreted by your healthcare provider. The following patterns are based on the information provided by MedlinePlus.

  • Higher than normal: May be a sign of an infection or an inflammatory or autoimmune condition affecting your central nervous system, such as multiple sclerosis, transverse myelitis, neurosyphilis, connective tissue disorders, Guillain-Barre syndrome, or herpes simplex encephalitis. Limitation: A CSF IgG test alone cannot diagnose a condition. You may need more tests before your provider can diagnose your condition. Next step: Your provider will likely order additional tests to confirm or rule out a specific diagnosis.
  • Lower than normal: May be a sign that your body is unable to make enough IgG antibodies, making you more likely to get infections. Experts don't know what causes this problem. Limitation: Normally, a test of IgG levels in blood is used to check whether you may lack IgG antibodies. This result alone does not confirm a diagnosis. Next step: Your provider may order a blood test to check your IgG levels and discuss further evaluation.
  • A CSF IgG test alone cannot diagnose multiple sclerosis or any other condition.
  • There is no specific test for multiple sclerosis.
  • Results must be interpreted by a healthcare professional in the context of your symptoms and other tests.
  • The test does not provide a definitive diagnosis; additional testing is often needed.

What to do next

If you have questions about your results, talk with your provider. You may need other tests to help diagnose or rule out a condition. While there is no cure for multiple sclerosis, there are treatments available to relieve symptoms and help keep it from getting worse.

  • What do my CSF IgG index results mean in my specific situation?
  • What other tests might I need to help diagnose my condition?
  • What are the next steps if my results suggest multiple sclerosis?
  • Can my symptoms be explained by something other than a central nervous system disorder?
  • How should I prepare for any follow-up tests or appointments?

Evidence source

U.S. National Library of Medicine: CSF Immunoglobulin G (IgG) Index

Browse all reviewed lab tests