Ordering Recommendation

Use to evaluate for Alzheimer's disease (AD) and other causes of cognitive impairment in adults aged 55 years or older with cognitive impairment. 

New York DOH Approval Status

This test is New York state approved.

Specimen Required

Patient Preparation
Collect

CSF

Specimen Preparation

Tube type:
Preferred: 2.5 ml low-bind polypropylene false bottom CSF tube (Sarstedt, 63.614.625), available in orderable collection kit, ARUP Supply # 58810.
Acceptable: Sarstedt 72.703.600 (1.5 ml) or Sarstedt 72.694.600 (2 ml) low-bind screw cap polypropylene microtube.
Unacceptable: Standard CSF polystyrene collection tubes are not acceptable as exposing CSF to polystyrene tubes may decrease Abeta42 concentrations.

Collection instructions:
1. Perform lumbar puncture and discard the first 1 to 2 ml of CSF
2. Using the drip method, collect CSF directly into low-bind polypropylene false bottom CSF tube (ARUP Supply #58810) available online through eSupply using ARUP Connect™ or contact ARUP Client Services at 800-522-2787. Avoid use of syringes or extension tubing. Fill tube at least 50% full.
3. Freeze and send specimen in original polypropylene collection tube (do not aliquot).

Storage/Transport Temperature

-20°C: Critical frozen

Unacceptable Conditions

Specimen types other than those listed and hemolyzed CSF. Specimens too viscous to be aspirated by instrument.

Remarks
Stability

Frozen: 8 weeks

Methodology

Quantitative Electrochemiluminescent Immunoassay (ECLIA)

Performed

Mon

Reported

1-7 days

Reference Interval

Test Number
Components
Reference Interval
  Phospho-Tau(181)/Abeta42 Ratio, CSF <= 0.023
  Total-Tau/Abeta42 Ratio, CSF <= 0.28

Interpretive Data

Interpretive information: The Alzheimer's Disease Markers, CSF panel is intended for use in adult patients aged 55 years and older being evaluated for Alzheimer's disease (AD) and other causes of cognitive impairment. The pTau181/Abeta42 and tTau/Abeta42 ratios provide better concordance with amyloid positron emission tomography (PET) imaging when compared to Abeta42, pTau181, and tTau individually.

Limitations:
Failure to adhere to the sample collection instructions provided in the Laboratory Test Directory may result in falsely reduced Abeta42 concentrations and therefore false elevations in the reported ratios. The ratios reported have not been established for predicting development of dementia or other neurologic conditions or for monitoring responses to therapies. Results of this test must always be interpreted in the context other clinical diagnostic evaluations and should not be used alone to establish a diagnosis of AD or other cognitive disorder.

Methodology:
Roche Diagnostics Inc. electrochemiluminescence assay was used. Results obtained with different assay methods or kits may be different and cannot be used interchangeably.


Phospho-Tau (181P) CSF/ß-Amyloid (1-42) CSF ratio Interpretation
<= 0.023 A negative result, defined as pTau181/Abeta42 ratio value below cutoff, is consistent with a negative amyloid positron emission tomography (PET) scan result. A negative result reduces the likelihood that a patients cognitive impairment is due to AD.
> 0.023 A positive result, defined as pTau181/Abeta42 ratio value above cutoff, is consistent with a positive amyloid PET scan result. A positive result does not establish a diagnosis of AD or other cognitive disorder.

Total Tau CSF/ß-Amyloid (1-42) CSF ratio Interpretation
<= 0.28 A negative result, defined as tTau/Abeta42 ratio value below cutoff, is consistent with a negative amyloid positron emission tomography (PET) scan result. A negative result reduces the likelihood that a patients cognitive impairment is due to AD.
> 0.28 A positive result, defined as tTau/Abeta42 ratio value above cutoff, is consistent with a positive amyloid PET scan result. A positive result does not establish a diagnosis of AD or other cognitive disorder.

Compliance Category

FDA

Note

Hotline History

N/A

CPT Codes

83520 x3

Components

Component Test Code* Component Chart Name LOINC
3017619 Phospho-Tau(181)/Abeta42 Ratio, CSF 97102-8
3017620 Total-Tau/Abeta42 Ratio, CSF 41027-4
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.

Aliases

Alzheimer's Disease Markers, CSF