Beta-Amyloid Ratio (1-42/1-40), Spinal Fluid
Use
Assisting in the evaluation of adult patients, aged 55 years and older, presenting with cognitive impairment and are being assessed for Alzheimer disease and other causes of cognitive decline. This test is used to measure the beta-amyloid ratio (1-42/1-40) in cerebrospinal fluid, which acts as a surrogate marker of amyloid plaque burden. This is due to increased deposition of beta-amyloid 1-42 in the brain. It is essential for differential diagnosis in suspected cases of Alzheimer's disease and may improve diagnostic accuracy by correlating with amyloid positron emission tomography (PET) scans.
Special Instructions
This test is intended for adults aged 55 years and older. For individuals 54 years or younger, a different test (ADEVL / Alzheimer Disease Evaluation, Spinal Fluid) is recommended. It is crucial not to collect CSF for the test if the patient is younger than 55 years. Collection should be done via lumbar puncture, collecting at least 50% of the container volume, and avoiding polystyrene tubes to prevent falsely low beta-amyloid concentrations.
Limitations
The test's safety and effectiveness have not been established for monitoring therapeutic effectiveness or predicting the development of dementia or other neurologic conditions. The results must be interpreted alongside other diagnostic tools such as neurological exams, lab tests, and imaging. The amyloid ratio does not correlate with disease severity, and different assay methods may lead to variable results. The presence of antibodies to mouse or other animal antibodies may affect immunoassay results, leading to inaccuracies.
New York Approved
Methodology
Immunoassay (CLIA)
Biomarkers
LOINC Codes
- 98485-6
- 98485-6
- 69048-7
Result Turnaround Time
1-7 days
Related Documents
For more information, please review the documents below
Specimen
Cerebrospinal Fluid
Volume
0.75 to 1.5 mL
Minimum Volume
Not provided
Container
Sarstedt 1.5 mL tube (Ref. 72.703.600), CSF AD Biomarker Tube (T833), Sarstedt 72.694.600, Sarstedt 62.610.018
Collection Instructions
Perform lumbar puncture using gravity drip method. Discard the first 1 to 2 mL of CSF. Avoid collecting CSF visibly contaminated with blood. Fill collection tubes at least 50% full. Freeze sample upright if transporting frozen, otherwise refrigerate and transport upright. Avoid using polystyrene tubes.
Causes for Rejection
Gross hemolysis, gross lipemia, gross icterus
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 48 hours |
| Refrigerated | 14 days |
| Frozen | 90 days |