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Amyloid Beta (Aβ) Protein, Cerebrospinal Fluid — Mass Concentration

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

Measures the amount of amyloid beta protein in cerebrospinal fluid. This test may be used with other biomarkers to help evaluate suspected Alzheimer's disease.

Quick summary

["Low CSF amyloid beta levels can support an Alzheimer's disease diagnosis, but the result must be interpreted with other tests."]

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

Key facts at a glance

LOINC
16343-6
Short code
A-AIB CSF-mCnc
Synonyms
A-AIB CSF-mCnc
Category
liver
Sample
csf
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

What is this test?

This test measures amyloid beta protein in cerebrospinal fluid, the fluid surrounding the brain and spinal cord. The specific amyloid beta form measured, such as Aβ42, depends on the laboratory order.

Why might I need this test?

A clinician may order this test when memory, thinking, or other neurologic symptoms raise concern for Alzheimer's disease or another dementia. It is usually interpreted along with cerebrospinal fluid or blood tests for tau and other Alzheimer biomarkers.

How is the test performed?

Cerebrospinal fluid is usually collected through a lumbar puncture, also called a spinal tap. The laboratory measures the concentration of amyloid beta protein using a laboratory method such as immunoassay.

How do I prepare for the test?

Fasting is generally not required, but follow your clinician's instructions about medicines and other tests. A lumbar puncture requires local anesthetic and may cause temporary back discomfort or a headache; tell the clinician if you have bleeding problems, take blood thinners, or have spinal conditions.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CSF Amyloid Beta

Frequently asked questions

Does this test diagnose Alzheimer's disease?
No. It can provide important evidence, but the result must be interpreted with other biomarkers, imaging, medical history, and a clinical evaluation.
Why is cerebrospinal fluid used instead of blood?
Cerebrospinal fluid may reflect changes in the brain more directly than blood. Collection generally requires a lumbar puncture.
Can other conditions affect the result?
Yes. Other neurologic disorders and normal aging can also alter cerebrospinal fluid amyloid beta levels, so isolated results should not be used to make a diagnosis.
  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