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HelpTest Code LAB8929 Alzheimer Disease Evaluation, Spinal Fluid
Additional Codes
ADEVL
Specimen Required
Supplies:
Alzheimer's Disease Evaluation (ADEVL) Collection Kit (T836)
CSF AD Biomarker Tubes (T833; also included in T836)
Container/Tube:
Preferred: Sarstedt CSF False Bottom Tube 63.614.625 (2.5 mL)
Acceptable: Sarstedt 72.703.600 (1.5 mL) or Sarstedt 72.694.600 (2 mL)
Specimen Volume: 1.5 to 2.5 mL
Collection 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.
4. Collection instructions can also be found on Spinal Fluid Specimen Collection Instructions for Alzheimer Disease Evaluation (T967).
Secondary ID
607273Useful For
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.
Method Name
Electrochemiluminescent Immunoassay (ECLIA)
Specimen Type
CSFSpecimen Minimum Volume
See Specimen Required
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| CSF | Refrigerated (preferred) | 14 days | BlueTop SARSTEDT |
| Frozen | 60 days | BlueTop SARSTEDT | |
| Ambient | 12 hours | BlueTop SARSTEDT |
Reject Due To
| Gross hemolysis | Reject |
| Gross lipemia | OK |
| Gross icterus | Reject |
Reference Values
Beta-amyloid (1-42) (Abeta42): >834 pg/mL
Total-Tau: ≤238 pg/mL
Phosphorylated-Tau 181: ≤21.6 pg/mL
p-Tau/Abeta42: ≤0.028
Interpretation
A beta-amyloid (1-42; Abeta42) result greater than 834 pg/mL is consistent with a negative amyloid positron emission tomography (PET) scan. A negative amyloid PET scan indicates the presence of no or sparse neuritic plaques and is inconsistent with a neuropathological diagnosis of Alzheimer disease (AD). An Abeta42 result greater than 834 pg/mL is associated with a reduced likelihood that a patient's cognitive impairment is due to AD.
Total Tau (t-Tau) and phosphorylated Tau (p-Tau181) cerebrospinal fluid (CSF) concentrations increase approximately 2 to 3-times as much in patients with mild-moderate AD as compared to age-matched controls. A t-Tau and/or p-Tau181 concentration of less than or equal to 238 pg/mL and less than or equal to 21.6 pg/mL, respectively, reduces the likelihood that a patient's cognitive impairment is due to AD.
The use of p-Tau181/Abeta42 ratio provides better concordance with amyloid PET scan when compared to Abeta42, p-Tau181, and t-Tau individually. The p-Tau/Abeta42 ratio provides better concordance with amyloid PET imaging when compared to Abeta42, phospho-Tau and total-Tau individually. A cut-off of 0.028 provides optimal balance between negative percent agreement (NPA) and positive percent agreement (PPA) when compared to amyloid PET results. A p-Tau/Abeta42 ratio of 0.028 or less has a 92% NPA with normal amyloid PET. A ratio above 0.028 has a 92% PPA with abnormal amyloid PET.
High CSF t-Tau protein concentrations are found in other neurodegenerative diseases such as prion disease or Creutzfeldt-Jakob disease (CJD). In this situation, an elevated t-Tau concentration and an increased t-Tau to p-Tau ratio has a very high specificity for differential diagnoses of CJD.
|
Abnormal (+)/normal (-) |
Individual comments for AD reporting values |
|
Abeta42 (-) phospho Tau (-) total Tau (-) |
Normal concentrations of Abeta42, phospho-Tau, and total-Tau concentrations are present in CSF. These results are not consistent with the presence of pathological changes associated with Alzheimer disease. |
|
Abeta42 (+) phospho-Tau (-) total-Tau (-) |
Abnormal Abeta42 concentrations are present in CSF. Phospho-Tau and total-Tau concentrations are normal. These results may be consistent with Alzheimer-related pathologic change. |
|
Abeta42 (+) phospho-Tau (+) total-Tau (-) |
Abnormal Abeta42 and phospho-Tau concentrations are present in CSF. The total-Tau concentration is normal. These results are consistent with the presence of Alzheimer disease. |
|
Abeta42 (+) phospho Tau (+) total Tau (+) |
Abnormal Abeta42, phospho-Tau and total-Tau concentrations are present in CSF. These results are consistent with the presence of Alzheimer disease. |
|
Abeta42 (+) phospho Tau (-) total Tau (+) |
Abnormal Abeta42, and total-Tau concentrations are present in CSF. The phospho-Tau concentration is normal. These results may be consistent with Alzheimer-related pathologic change. |
|
Abeta42 (-) phospho-Tau (+) total-Tau (-) |
Abnormal phospho-Tau concentrations are present in CSF. Abeta42 and total-Tau concentrations are normal. These results are not consistent with the presence of pathological changes associated with Alzheimer disease. |
|
Abeta42 (-) phospho tau (-) total-Tau (+) |
Abnormal total-Tau concentrations are present in CSF. The Abeta42 and phospho-Tau concentrations are normal. These results are not consistent with the presence of pathological changes associated with Alzheimer disease. |
|
Abeta42 (-) phospho-Tau (+) total-Tau (+) |
Abnormal phospho-Tau and total-Tau concentrations are present in CSF. The Abeta42 concentration is normal. These results are not consistent with the presence of pathological changes associated with Alzheimer disease. |
This table and interpretations are based on the National Institute on Aging and Alzheimer's Association research framework diagnostic recommendations.
Method Description
Beta-amyloid (1-42):
The Roche cobas assay for determining beta-amyloid (1-42) in cerebrospinal fluid (CSF) uses a sandwich assay principle. A biotinylated monoclonal beta-amyloid (1-42) antibody and a monoclonal beta-amyloid (1-42) specific antibody labeled with a ruthenium complex react to form a sandwich complex. Streptavidin-coated microparticles are added, and the interaction between biotin and streptavidin allows the complex to become bound to the solid phase. The reaction mixture is then aspirated into the measuring cell, microparticles are captured onto the electrode, and the application of voltage induces chemiluminescent emission, which is measured by a photomultiplier.(Package insert: Elecsys beta-Amyloid (1-42) CSF II. Roche Diagnostics; Version 1.0, 12/2022)
Total-Tau:
The Roche cobas assay for determining total-Tau in CSF uses a sandwich assay principle. Two biotinylated monoclonal Tau-specific antibodies and a monoclonal Tau-specific antibody labeled with a ruthenium complex react to form a sandwich complex. Streptavidin-coated microparticles are added, and the interaction between biotin and streptavidin allows the complex to become bound to the solid phase. The reaction mixture is then aspirated into the measuring cell, microparticles are captured onto the electrode, and the application of voltage induces chemiluminescent emission, which is measured by a photomultiplier.(Package insert: Elecsys Total-Tau CSF. Roche Diagnostics; Version 2.0, 10/2023)
Phospho-Tau:
The Roche cobas assay for determining phospho-Tau in CSF uses a sandwich assay principle. A biotinylated monoclonal antibody specific for phosphorylation at threonine 181 and a monoclonal Tau-specific antibody labeled with a ruthenium complex react to form a sandwich complex. Streptavidin-coated microparticles are added, and the interaction between biotin and streptavidin allows the complex to become bound to the solid phase. The reaction mixture is then aspirated into the measuring cell, microparticles are captured onto the electrode, and the application of voltage induces chemiluminescent emission, which is measured by a photomultiplier.(Package insert: Elecsys Phospho-Tau (181P) CSF. Roche Diagnostics; Version 1.0, 12/2022)
Day(s) Performed
Tuesday, Thursday, Friday
Report Available
1 to 4 daysSpecimen Retention Time
12 monthsPerforming Laboratory
Mayo Clinic Laboratories in Rochester
CPT Code Information
83520 x 3
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| ADEVL | Alzheimer's Disease Evaluation, CSF | 104134-2 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| PTABR | p-Tau/Abeta42 | 41027-4 |
| ADINT | AD Interpretation | 69048-7 |
| AB42P | Abeta42 | 33203-1 |
| TTAUP | Total-Tau | 30160-6 |
| PTAUP | Phospho-Tau(181P) | 72260-3 |
Forms
If not ordering electronically, complete, print, and send a Neurology Specialty Testing Client Test Request (T732) with the specimen.