Test Overview
Clinical Utility
Quest Diagnostics does not perform this test for individuals under the age of 18. Pre-test and post-test counseling is strongly recommended.
Method
Liquid chromatography-tandem mass spectrometry (LC-MS/MS)
Method Description
This LC-MS/MS assay measures beta-amyloid 40 (AB40) as well as AB42 in cerebrospinal fluid (CSF), rather than AB42 alone. This permits the normalization of beta amyloid levels circulating in CSF in different patients. Using the ratio of beta-amyloid 42/beta-amyloid 40, improves sensitivity and specificity for detecting Alzheimer’s disease.
Result Included
Amyloid beta peptide 42; Amyloid beta peptide 40; Amyloid beta peptide 42/40 Ratio
Aliases/Synonyms
Amyloid Beta 42/40 Ratio
Specimen
Specimen Type
CSFVolume
Sample Volume
0.5 mL
Minimum Volume
0.3 mL
Specimen Comment
Quest Diagnostics does not perform this test for individuals under the age of 18. Pre-test and post-test counseling is strongly recommended.
Collection & Handling
Collection Instructions
Do not use glass, polystyrene or polycarbonate tubes.
Handling Information
Do not collect or transfer in a glass, polystyrene, or polycarbonate tube.
Store and send frozen.
Stability
| Ambient | Refrigerated | Frozen |
|---|---|---|
| 72 hours | 5 days | 31 days |
Rejection Criteria
| Criteria | Specification |
|---|---|
| Age | Under 18 |
| Hemolysis | Moderate or gross |
| Lipemia | Gross |
| Specimen | Collected in a glass, polystyrene, or polycarbonate tube |
| Other | Moderately or grossly icteric |
Performance & Interpretation
Turnaround Time
15 days
Referral Location
Out-of-Country
Interface & Setup
HL7 Interface Codes
| Order Code | Result Name | Result Codes | Units |
|---|---|---|---|
| BARATIO SF | ABETA 42 | 63144 | pg/mL |
| ABETA 40 | 63145 | pg/mL | |
| ABETA 42/40 RATIO | 63146 | None |
Test Version
Last Updated
2025-01-06