Cerebrospinal fluid (CSF) is a clear bodily fluid that cushions and protects your brain and spinal cord. A CSF protein test involves taking a fluid sample from your spinal column using a needle. This procedure is known as a lumbar puncture or spinal tap.
The CSF protein test determines if there’s too much or too little protein in your CSF. Test results that indicate your protein level is higher or lower than normal can help your doctor diagnose a range of conditions. Another use for a CSF protein test is to check the amount of pressure in your spinal fluid.
Your doctor will order a CSF protein test if they suspect you have a central nervous system disease such as multiple sclerosis (MS) or an infectious condition such as meningitis. CSF protein tests are also helpful when looking for signs of injury, bleeding in the spinal fluid, or vasculitis.
High levels of protein in your CSF can indicate:
- aseptic meningitis
- bacterial meningitis
- brain abscess
- brain tumor
- cerebral hemorrhage
Acute alcoholism is another possible cause of high protein levels.
Low levels of protein in your CSF could mean your body is leaking cerebrospinal fluid. This could be due to a traumatic injury such as head trauma or a stabbing.
Your doctor will need to know if you’re taking any blood-thinning medications such as heparin, warfarin, or aspirin. Give your doctor a complete list of medications you take. Make sure to include both prescription and over-the-counter medicines.
Let them know if you have a history of back or spinal problems, or neurological illnesses or conditions. Tell your doctor if your work is strenuous and involves using your back. You may need to not work on the day of your test.
Expect to rest for at least an hour after your test is complete.
The lumbar puncture for your CSF protein test will take place at a hospital or clinic. You’ll need to change into a hospital gown that opens in the back. This gives the doctor easy access to your spine.
Your doctor will ask you to lie on an exam table or hospital bed, turn on your side, and expose your back. You might also sit up and bend over.
Your doctor will clean your back with antiseptic and apply a local anesthetic. This will numb the puncture site to minimize pain. It may take a few moments to start working.
Your doctor will then insert a hollow needle into your lower spine. They’ll draw a small amount of CSF into the needle. You must hold very still.
Your doctor will remove the needle after collecting enough fluid. They’ll clean and bandage the insertion site. Then they’ll send your CSF sample to a laboratory for analysis.
You can expect to rest for an hour or two after the test. Your doctor may suggest you take a mild pain reliever.
Lumbar puncture is very common and considered generally safe when done by a trained and experienced doctor. However, there are some medical risks, including:
- bleeding into the spine
- allergic reaction to anesthetic
- damage to the spinal cord (if you move)
- brain herniation (if a brain mass is present)
There is usually some discomfort during the test that may last a little while after the test.
Many people have a headache after a lumbar puncture. This should go away within 24 hours. Let your doctor know if it doesn’t.
Your test results should be ready in a couple of days. According to the American Academy of Family Physicians, the normal range for an adult’s protein level is 18 to 58 milligrams per deciliter (mg/dL). Milligrams per deciliter is a measurement that looks at the concentration of something in an amount of fluid.
Different laboratories have different ranges they consider normal, so speak with your doctor to find out what your laboratory’s normal range is.
Your doctor will analyze your test results and discuss them with you. If protein levels in your cerebrospinal fluid are higher or lower than normal, your doctor can use these measurements to diagnose a condition.