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Test Code C2AD2 PrecivityAD2, Plasma


Ordering Guidance


This blood test is intended for use in patients aged 55 and older with signs or symptoms of mild cognitive impairment or dementia who are undergoing evaluation for Alzheimer disease or other forms of cognitive decline.



Shipping Instructions


1. Specimens must be shipped frozen on dry ice.

2. Place labeled aliquot tubes inside a larger tube or vial for transport.



Specimen Required


Supplies: Screw cap micro tube, 2 mL, PCR Performance Tested, Low protein-binding (T983)

Collection Container/Tube: 10 mL Purple top (K EDTA)

Submission Container/Tube: Two 2-mL screw cap micro tubes

Specimen Volume: 3 mL in 2 tubes, each containing 1.5 mL

Collection Instructions:

1. Centrifuge within two hours of collection.

2. Label two 2-mL screw-cap micro tubes.

3. Aliquot 1.5 mL of plasma into each labeled micro tube.

4. Freeze plasma (no longer than 2 hours after collection) at or below -20° C.


Useful For

Assisting in the evaluation of adult patients, aged 55 years and older, with signs or symptoms of mild cognitive impairment or dementia who are being assessed for Alzheimer disease and other causes of cognitive decline

 

This is not intended for patients younger than 55 years, or for use as a screening test in patients without signs or symptoms of cognitive impairment, or for serial testing for assessment of longitudinal changes.

Method Name

Immunoprecipitation/Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)

Reporting Name

PrecivityAD2

Specimen Type

Plasma

Specimen Minimum Volume

See Specimen Required

Specimen Stability Information

Specimen Type Temperature Time Special Container
Plasma Frozen

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject
Outside of age range
Specimen collected outside of testing range (too long in storage before arrival to testing facility)
Insufficient volume
Incorrect labeling		 Reject

Clinical Information

Alzheimer disease (AD) is defined pathologically by the presence of amyloid plaques and neurofibrillary tangles in the brain. Clinical characteristics include gradual onset of mild cognitive impairment (MCI), behavioral changes such as apathy, withdrawal, or agitation, and disease progression to middle and later stage dementia.(1,2) Currently, no test detects AD with 100% accuracy; definitive diagnosis occurs at brain autopsy.

 

Recent availability of anti-amyloid therapies increases the importance of detection of AD at an early stage.(3-5) MCI impacts 12 to 18% of people in the United States over age 60 and is often an initial clinical sign of AD.(6) Establishing or excluding an AD diagnosis with a high degree of certainty at first signs of memory decline may optimize medical management.

 

Brain amyloid pathology is detectable by amyloid positron emission tomography (PET) scan, cerebrospinal fluid testing, or liquid chromatography tandem mass spectrometry blood biomarker testing with high sensitivity and specificity in patients with MCI and early dementia.(7-12) In all testing modalities, healthcare providers interpret test results in the context of the patient's clinical findings and other clinical work-up, as the neuropathological changes associated with AD can be seen in other forms of dementia and in unaffected individuals.(7,8,13)

 

The PrecivityAD2 test is an analytically and clinically validated blood test that aids healthcare providers in ruling in or ruling out AD in patients presenting with MCI or dementia. This evaluation simultaneously quantifies specific plasma amyloid beta (Abeta) and tau peptide concentrations to calculate the Abeta42/40 ratio and percent tau phosphorylated at threonine-217 (%p-tau217).(12) The inclusion of plasma analyte ratios has been shown to mitigate the effects of confounding factors such as chronic kidney disease.(14,15) The ratios are combined into a proprietary statistical algorithm to calculate the Amyloid Probability Score 2 (APS2), a numerical value ranging from 0 to100 that determines whether a patient is positive (has high likelihood) or negative (has low likelihood) for the presence of brain amyloid plaques by amyloid PET scan.

Reference Values

Amyloid Probability Score 2 (APS2) (range of 0-100):

Negative: 0-47

Positive: 48-100

 

Abeta42/40 Ratio:

≥0.095 Consistent with absence of amyloid plaques

 

Percent p-tau217:

<4.2% consistent with absence of brain amyloid plaques

Interpretation

The Amyloid Probability Score 2 (APS2) result is a composite score ranging from 0 to 100 that demonstrates the strongest correlation with brain amyloid pathology compared to the individual biomarkers (amyloid beta [Abeta] 42/40 ratio or percent tau phosphorylated at threonine-217 [%p-tau217]) considered separately. Discordance of the individual biomarkers can occur.

 

Table. Amyloid Probability Score and Interpretation

APS2

Interpretation

0-47

Negative

Consistent with a negative amyloid positron emission tomography (PET) scan; reflects a low likelihood of brain amyloid plaques and is therefore not consistent with a neuropathological diagnosis of Alzheimer disease (AD).

48-100

Positive

Consistent with a positive amyloid PET scan; reflects a high likelihood of brain amyloid plaques, one of the neuropathological findings of AD.

 

The APS2 result should be interpreted in conjunction with other patient information. Clinical correlation is recommended.

Day(s) Performed

Monday through Friday

Report Available

10 days post sample receipt from MCL.

Specimen Retention Time

60 days

Performing Laboratory

C2N Diagnostics LLC

Test Classification

C2N Diagnostics has developed and determined the analytical and clinical validity performance characteristics of this Laboratory Developed Test (LDT). This assay has been validated pursuant to CLIA regulations and is used for clinical purposes. This assay has not been cleared or approved by the FDA.

CPT Code Information

0503U

LOINC Code Information

Test ID Test Order Name Order LOINC Value
C2AD2 PrecivityAD2 Not Provided

 

Result ID Test Result Name Result LOINC Value
AD2C Amyloid Probability Score 2 (APS2) Not Provided
AD2CF APS2 Result Not Provided
AD2D APS2 Result Interpretation Not Provided
AD2E APS2 Result Reference Interval Not Provided
AD2F APS2 Description Not Provided
AD2G Percent p-tau217 Not Provided
AD2H Percent p-tau217 Reference Interval Not Provided
AD2HD Percent p-tau217 Description Not Provided
AD2I Abeta42/40 Ratio Not Provided
AD2J Abeta42/40 Ratio Reference Interval Not Provided
AD2JD Abeta42/40 Ratio Description Not Provided
AD2K Test Description Not Provided
AD2L Limitations of Test Result Not Provided
AD2M Methods and Assay Category Not Provided
AD2N References Not Provided
AD2O Report Comment Not Provided
AD2P Performing Site Not Provided