Laboratory Services

Alzheimer Disease Evaluation, Spinal Fluid

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Updated Test Information:

Test Description
Alzheimer Disease Evaluation, Spinal Fluid

Amyloid Beta 42, Beta-Amyloid 42, ABeta, Total Tau, Phosphorylated Tau, pTau, tTau

Test ID
General Information

Assessment of adults with cognitive impairment being evaluated for Alzheimer disease and other causes of cognitive impairment

These assays should not be used to predict the development of dementia or other neurologic conditions or to monitor response to therapies.

Measurement of beta-amyloid (1-42)(Abeta42), total-Tau, and phosphorylated-Tau (p-Tau181) in cerebrospinal fluid is useful in the differential diagnosis of Alzheimer Disease (AD) and other causes of cognitive impairment.

The p-Tau181/Abeta42 ratio provides excellent concordance with amyloid positron emission tomography (PET) imaging to assess the presence of amyloid deposition in patients with AD.

Container Type

Sterile Tube

Specimen Type


Specimen Requirements

1.5 to 2.5 mL

Specimen Collection / Processing Instructions

1. Perform lumbar puncture and discard the first 1 to 2 mL of cerebrospinal fluid (CSF).

2. Collect CSF directly into one of the listed collection tubes until the tube is at least 50% full.*

3. Send CSF specimen in original collection tube. Do not aliquot.

Note: Polystyrene collection tubes are not acceptable. Exposure of CSF to polystyrene tubes may result in falsely low Abeta42 concentrations. For more information see Cautions.

*The Alzheimer's Association consensus protocol for handling of CSF for clinical measurements of Abeta42 and tau recommends using the drip method for CSF collection and directly collecting into a low bind polypropylene tube. Although some clinicians prefer the syringe pull method due to speed of collection, the drip method reduces the risk of Abeta42 binding to the plastic of any syringe used.


Refrigerated (preferred) 14 days
Frozen 60 days
Ambient 12 hours

Unacceptable Specimen Conditions

Samples in Polystyreen collection tubes, Gross hemolysis, Gross icterus


Electrochemiluminescent Immunoassay (ECLIA)

Estimated TAT

1 to 4 days

Testing Schedule

Tuesday, Friday


12 months

CPT Code(s)

83520 x 3

Reference Range

Beta-amyloid (1-42) (Abeta42): >834 pg/mL

Total-Tau: < or =238 pg/mL

Phosphorylated-Tau 181: < or =21.6 pg/mL

p-Tau/Abeta42: < or =0.028

Performing Lab


LOINC Code(s)