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Cerebrospinal Fluid Protein Mass Concentration (Free Fraction)

Published: August 9, 2026Updated: August 16, 2026

This test measures the total amount of protein in your cerebrospinal fluid (CSF), focusing on the portion that is not bound to other substances. CSF protein levels can help diagnose conditions affecting the brain and spinal cord.

Quick summary

["Understanding your CSF protein levels may help identify nerve or brain issues."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
59231-1
Short code
PSA Free CSF-mCnc
Synonyms
PSA Free CSF-mCnc
Category
chemistry
Sample
csf
Container
Sterile tube
Units
N/A
Ref low
0
Ref high
4
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84153
SNOMED
39392002
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

Why This Test Is Done

Doctors may order this test if you have symptoms like headaches, vision changes, numbness, weakness, or neurological problems. It can also be part of investigations for conditions such as infections, tumors, multiple sclerosis, or other inflammatory diseases of the central nervous system.

What to Expect Before the Test

You’ll likely have a lumbar puncture (spinal tap), where a small needle is inserted into your lower back to collect CSF. This procedure is usually done in a hospital setting with monitoring. You may feel mild discomfort, but it’s generally quick and well-tolerated.

What the Results Mean

Elevated levels of free protein in CSF can signal inflammation, infection, or other abnormalities in the brain or spinal cord. Lower-than-expected levels might suggest certain genetic or metabolic disorders. Your doctor will interpret results in the context of your symptoms and medical history.

Common Conditions Linked to Abnormal Results

High CSF protein levels may be associated with conditions like meningitis, encephalitis, multiple sclerosis, or tumors. Low levels could be linked to rare genetic disorders or certain metabolic conditions. Always discuss your results with your healthcare provider.

Reference range

Normal: <4.0 ng/mLN/A

Specimen: csf

No special preparation required. For PSA, avoid sexual activity for 24-48 hours before the test.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CSF Free Protein Level

Frequently asked questions

What does a high CSF protein level usually indicate?
A high level of free protein in CSF often suggests inflammation, infection, or damage to the brain or spinal cord. This could be due to conditions like meningitis, multiple sclerosis, or certain tumors. Your doctor will review your symptoms and other test results to determine the cause.
How is this test different from a general protein test in blood?
This test specifically measures protein in cerebrospinal fluid, which is the fluid surrounding your brain and spinal cord. Blood protein tests measure proteins in your bloodstream, so results can differ based on the body’s fluid involved and the underlying condition affecting those fluids.
Can diet affect the results of this test?
Diet generally does not affect CSF protein levels, as this fluid is produced within the brain and spinal cord. However, avoid strenuous activity or certain medications before your procedure, as instructed by your healthcare provider, to ensure accurate results.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy