Overview


Alzheimer’s disease (AD) is a neurodegenerative disorder hallmarked by extracellular amyloid-beta (AB) plaques and intracellular neurofibrillary tangles of hyperphosphorylated tau (p-tau), which lead to progressive loss of neuronal function and cell death. These pathologies can be present and developing in the brain for years before any symptoms become apparent. During this buildup there are several specific proteins that are released into the cerebrospinal fluid (CSF) that have been identified as reliable biomarkers for the diagnosis of AD.

This test is intended for assessing the underlying AD-associated pathology in conjunction with clinical assessment to increase diagnostic certainty.

Test code:

Aβ42/40
Abbreviations, alternative names:

CSF Aβ42/40, Amyloid-beta ratio
Methodology:

Chemiluminescent enzyme immunoassay (CLEIA)
Validation:

In Vitro Diagnostic (IVD)

Requirements


Specimen type:

Cerebrospinal fluid
Minimum volume:

0.5 mL
Preferred volume:

1.5 mL
Rejection criteria:

Sample arrives thawed; quantity not sufficient; gross hemolysis

Our offices are only able to receive samples Mon-Fri, so samples must be shipped Mon-Thur. Samples arriving over the weekend may need to be re-drawn.

Specimen


Amyloid-beta has been shown to adhere to the surface of collection tubes, resulting in artificially low fluid concentrations. Because lower concentrations are associated with AD pathology, improper handling can result in erroneous positive results. It is critical to use low-bind collection tubes, and to not transfer sample from the original collection tube.

Specimen collection:

Collect cerebral spinal fluid (CSF) directly into Sarstedt Liquor low protein binding tubes
If first 1mL collected is hemolyzed, discard and continue collection with a new Sarstedt tube
Specimen handling:

Samples cannot be aliquoted from another tube into CSF tube.
Specimen storage:

Freeze upright immediately after collection to prevent contact with tube cap
Ship on dry ice
Specimen stability:

CSF may be stored:
Up to 48 hrs at room temp (15 - 25°C)
Up to 8 days refrigerated (2 - 8⁰C)
Up to 2 weeks at -20⁰C
Up to 1 months at -70⁰C
≤ 1 freeze/thaw is acceptable.
Do not freeze blood contaminated CSF for testing.

Performance


Testing frequency:

Once per week
Turnaround time:

1-3 days
Reference range:

Positive ≤ 0.058
Likely positive 0.059 – 0.072
Negative ≥ 0.073
Validation:

In vitro diagnostic (IVD)

Additional Information


  • Not intended to be used as a stand-alone test; the test results must be interpreted in conjunction with other diagnostic tools and clinical information.
  • A positive result is associated with the presence of amyloid plaques or neurofibrillary tangles in the brain but does not establish a diagnosis of AD as would be established by neuropathological examination.
  • Heterophilic antibodies in human serum can react with reagent immunoglobulins, interfering with immunoassays. People routinely exposed to animals or animal serum products or who have received mouse monoclonal antibodies for diagnosis or therapy can be prone to this interference. Such specimens may show either falsely elevated or falsely depressed values.
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