Test Id : AD2
PrecivityAD2, Plasma
Useful For
Suggests clinical disorders or settings where the test may be helpful
Assisting in the evaluation of adults aged 40 years and older, who present with signs or symptoms of cognitive impairment undergoing evaluation for Alzheimer disease or other forms of cognitive decline
This test is not intended for use as a screening or stand-alone diagnostic test. The safety and effectiveness of the PrecivityAD2 test have not been established for predicting development of dementia or other neurologic conditions, or for monitoring responses to therapies.
Highlights
The PrecivityAD2 test is a US Food and Drug Administration-cleared blood test that helps healthcare professionals evaluate whether a patient's cognitive symptoms are likely to be due to Alzheimer disease. The PrecivityAD2 test is indicated for use in adults aged 40 years and older who present with signs or symptoms of cognitive impairment undergoing evaluation for Alzheimer disease or other forms of cognitive decline. The PrecivityAD2 test is intended to be used in conjunction with clinical assessment to aid healthcare professionals experienced in the evaluation of cognitive impairment to identify patients with amyloid pathology associated with Alzheimer disease. The test is not intended as a screening or stand-alone diagnostic test.
The test measures plasma amyloid beta 42/40 ratio and percent tau phosphorylated at threonine-217. The two ratios are combined in a proprietary algorithm to calculate the Amyloid Probability Score 2 (APS2), a whole number from 0 to 100 reported as negative, likely positive, or positive. Only the APS2 result with reference intervals in the interpretation is reported.
Method Name
A short description of the method used to perform the test
Immunoprecipitation/Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.
Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test
Aliases
Lists additional common names for a test, as an aid in searching
%p-tau217
AB42/40 Ratio
Alzheimer's
Amyloid Beta
Amyloid Probability Score2
C2N
Dementia
Mild cognitive impairment
p-tau217
p-tau217 Ratio
Percent p-tau217
PrecivityAD2
Alzheimer Disease
Specimen Type
Describes the specimen type validated for testing
Plasma
Ordering Guidance
This blood test is intended for use in adults aged 40 years and older who present with signs or symptoms of cognitive impairment undergoing evaluation for Alzheimer disease or other forms of cognitive decline. The test is not intended as a screening or stand-alone diagnostic test.
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
Defines the optimal specimen required to perform the test and the preferred volume to complete testing
Supplies: Screw cap micro tube, 2 mL, PCR Performance Tested, Low protein-binding (T983)
Collection Container/Tube: 10 mL Purple top (K2-EDTA)
Submission Container/Tube: Two 2-mL screw cap micro tubes
Specimen Volume: 3 mL Plasma in 2 tubes, each containing 1.5 mL plasma
Collection Instructions:
1. Label two 2-mL screw-cap micro tubes.
2. Within 2 hours of collection, centrifuge and aliquot 1.5 mL of plasma into each labeled micro tube.
3. Freeze plasma (no longer than 2 hours after collection) at or below -20 degrees C.
Note: If plasma sample is not being shipped on the day of collection/processing, the sample needs to be stored at -80 degrees C.
Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.
See Specimen Required
Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected
| Gross hemolysis | Reject |
| Gross lipemia | Reject |
| Gross icterus | Reject |
| Outside of age range | Reject |
| Specimen collected outside of testing range (too long in storage before arrival to testing facility) | Reject |
| Insufficient volume | Reject |
| Incorrect labeling | Reject |
Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Plasma | Frozen | ||
Useful For
Suggests clinical disorders or settings where the test may be helpful
Assisting in the evaluation of adults aged 40 years and older, who present with signs or symptoms of cognitive impairment undergoing evaluation for Alzheimer disease or other forms of cognitive decline
This test is not intended for use as a screening or stand-alone diagnostic test. The safety and effectiveness of the PrecivityAD2 test have not been established for predicting development of dementia or other neurologic conditions, or for monitoring responses to therapies.
Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
The US Food and Drug Administration-cleared PrecivityAD2 test directly quantifies 4 plasma analytes using immunoprecipitation followed by liquid chromatography tandem mass spectrometry. These measurements are combined into two ratios: plasma amyloid beta 42/40 ratio (Abeta42/40) and the percentage of tau phosphorylated at threonine-217 (%p-tau217). Measuring each biomarker against its own reference protein improves diagnostic performance compared with individual biomarker concentrations alone. This approach improves specificity for amyloid pathology in the presence of advancing age and comorbidities commonly associated with aging, such as chronic kidney disease, obesity, and anemia.(1-6)
Results are reported as positive, negative, or likely positive. A positive or negative result is intended to help the healthcare professional rule in or rule out amyloid pathology associated with Alzheimer disease. When combined with clinical assessment, these results help improve diagnostic accuracy compared with clinical assessment alone. A likely positive result suggests the presence of amyloid pathology. It identifies the smaller group of patients whose biomarker profiles fall between the high and low-cut points, where additional evaluation or testing may be appropriate.
The clinical performance of this test was evaluated in a multicohort study of 1142 patients with subjective cognitive decline, mild cognitive impairment, or dementia. The test demonstrated high predictive value for brain amyloid status, as determined by amyloid positron emission tomography (PET; visual read) or cerebrospinal fluid biomarker analysis. At an overall brain amyloid prevalence of 52.7%, the positive predictive value (PPV) of a positive result was 97.6%. The negative predictive value (NPV) of a negative result was 93.1%, derived from the 6.9% predictive value for brain amyloid pathology among patients with negative results.(7) The PPV of a likely positive result was 77.3%. Likely positive results occurred in 17.3% of patients. Diagnostic performance was consistent across symptom severity, ages ranging from 40 to older than 80 years, and the number of comorbidities (one, two, or three or more). Comorbidities included atrial fibrillation, autoimmune or inflammatory disease, chronic heart failure, chronic kidney disease, coronary heart disease, depression, diabetes, dyslipidemia, history of cancer, history of stroke or transient ischemic attack, hypertension, and obesity.(7)
Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
Amyloid Probability Score 2 (APS2) (range of 0-100):
Positive
>66.5 is consistent with brain amyloid pathology
Likely Positive
>27.5 to < 66.5 is likely consistent with brain amyloid pathology
Negative
<27.5 is not consistent with brain amyloid pathology
APS2 results are reported as whole numbers from 0-100. The reporting ranges shown above are based on the APS2 cut points specified in the FDA-cleared PrecivityAD2 labeling.
Interpretation
Provides information to assist in interpretation of the test results
Table. Amyloid Probability Score 2 (APS2) Clinical Cutoffs and Test Result Interpretation
| APS2 Value | Result | Result interpretation |
| APS2 > 66.5 | Positive | An APS2 result >66.5 is Positive and consistent with the presence of brain amyloid pathology. This result increases the likelihood that a patient’s clinical presentation is due to Alzheimer disease. The APS2 result alone does not establish a diagnosis of clinical Alzheimer disease. Clinical correlation is recommended. |
| APS2 > 27.5 to < 66.5 | Likely Positive | An APS2 result >27.5 and <66.5 is Likely Positive and likely consistent with the presence of brain amyloid pathology. The result increases the likelihood that a patient’s clinical presentation is due to Alzheimer disease. The APS2 result alone does not establish a diagnosis of clinical Alzheimer disease. Additional evaluations or further testing may be appropriate. |
| APS2 < 27.5 | Negative | An APS2 result <27.5 is Negative and not consistent with the presence of brain amyloid pathology. The result decreases the likelihood that a patient's clinical presentation is due to Alzheimer disease. Other potential causes for the patient's cognitive symptoms should be considered. |
Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
The results of other analyte tests using other methodologies cannot be interpreted in the context of the PrecivityAD2 test.
Limitations:
The PrecivityAD2 test is for prescription use only.
The PrecivityAD2 test is for in vitro diagnostic use: only performed at C2N Diagnostics Laboratory.
This test is intended to be performed only on qualified, serial number-controlled instruments at C2N Diagnostics Laboratory. All instruments used for patient testing are controlled under C2N's Quality Management System and must successfully complete the required qualification and validation activities before implementation.
Always interpret the PrecivityAD2 test in conjunction with the patient's medical history, clinical presentation, physical assessment, and other findings.
The safety and effectiveness of the PrecivityAD2 test have not been established for:
-Predicting development of dementia or other neurologic conditions
-Monitoring responses to therapies
The performance of the PrecivityAD2 test across racial subgroups has not been fully established because of the relatively small number of subjects who report racial categories other than White and the large proportion of subjects in the pooled validation cohort with missing racial categorization. Results for these subgroups should be interpreted with caution.
Warnings:
Erroneous results may occur due to improper specimen collection, handling, storage, shipping, or unevaluated interfering substances.
Hemoglobin concentrations over 150 mg/dL may interfere with analyte measurement and affect the Amyloid Probability Score 2 result.
Clinical Reference
Recommendations for in-depth reading of a clinical nature
1. Meyer MR, Kirmess KM, Eastwood S, et al. Clinical validation of the PrecivityAD2 blood test: A mass spectrometry-based test with algorithm combining %p-tau217 and Abeta42/40 ratio to identify presence of brain amyloid. Alzheimers Dement. 2024;20(5):3179-3192. doi:10.1002/alz.13764
2. Karlsson L, Janelidze S, Barthelemy NR, et al. Reference proteins to improve Core 1 and Core 2 Alzheimer's disease CSF and plasma biomarkers. Brain. 2026;149(4):1153-1167. doi:10.1093/brain/awaf375
3. Bornhorst JA, Lundgreen CS, Weigand SD, et al. Quantitative assessment of the effect of chronic kidney disease on plasma P-Tau217 concentrations. Neurology. 2025;104(3):e210287. doi:10.1212/WNL.0000000000210287
4. Yun J, Lee J, Shin D, et al. Plasma phosphorylated Tau 217 cutoffs for amyloid pathology and kidney function, body mass index, and anemia. JAMA Neurol. 2026;83(3):269-279. doi:10.1001/jamaneurol.2025.5530
5. Pichet Binette A, Janelidze S, Cullen N, et al. Confounding factors of Alzheimer's disease plasma biomarkers and their impact on clinical performance. Alzheimers Dement. 2023;19(4):1403-1414. doi:10.1002/alz.12787
6. Palmqvist S, Warmenhoven N, Anastasi F, et al. Plasma phospho-tau217 for Alzheimer's disease diagnosis in primary and secondary care using a fully automated platform. Nat Med. 2025;31(6):2036-2043. doi:10.1038/s41591-025-03622-w
7. C2N Diagnostics, LLC. PrecivityAD2 test labeling. 510(k) K253240. Issued August 17, 2026. Available at www.accessdata.fda.gov/cdrh_docs/pdf25/K253240.pdf
8. Jack CR Jr, Andrews JS, Beach TG, et al. Revised criteria for diagnosis and staging of Alzheimer’s disease: Alzheimer’s Association Workgroup. Alzheimers Dement. 2024;20(8):5143-5169. doi:10.1002/alz.13859
Method Description
Describes how the test is performed and provides a method-specific reference
Liquid chromatography tandem mass spectrometry (LC-MS/MS) following immunoprecipitation is utilized for quantification of concentrations of AD Core 1 biomarkers (Abeta42 and p-tau217) and their reference proteins (Abeta40 and np-tau217) for normalizing ratio calculations. A proprietary algorithm combines Abeta42/40 ratio and p-tau217/np-tau217 X 100 (%p-tau217) to generate the Amyloid Probability Score 2 (APS2), a whole number ranging from 0-100, that determines whether a patient is positive, likely positive or negative for the presence of brain amyloid pathology.
PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information
Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.
Monday through Friday
Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.
Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location
Indicates the location of the laboratory that performs the test
Fees
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.
- Authorized users can sign in to Test Prices for detailed fee information.
- Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
- Prospective clients should contact their account representative. For assistance, contact Customer Service.
Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.
This test has been cleared by the U.S. Food and Drug Administration (FDA) under 510(k) K253240 and is performed according to the FDA-cleared labeling at C2N Diagnostics Laboratory. For prescription use only.
CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
CPT codes are provided by the performing laboratory.
CPT codes are provided by the performing laboratory.
0503U
LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.
| Test Id | Test Order Name | Order LOINC Value |
|---|---|---|
| AD2 | PrecivityAD2 | Not Provided |
| Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
|---|---|---|
| PD2A | Amyloid Probability Score | Not Provided |
| PD2B | APS2 Result | Not Provided |
| PD2C | Interpretation | Not Provided |
| PD2D | Indication for Use of the Test | Not Provided |
| PD2E | Test Description and Clinical Performance | Not Provided |
| PD2F | Limitations | Not Provided |
| PD2G | Report Comment | Not Provided |
| PD2H | Performing Site | Not Provided |