p-Tau 181/AB-42 Ratio
7 days
Chemiluminescent enzyme immunoassay (CLEIA)
Reduced likelihood of cerebral amyloid pathology ≤0.068
A normal CSF p-Tau181/Amyloid beta-42 ratio (<=0.068) is not supportive of an Alzheimer’s disease-related biomarker profile and is associated with a lower likelihood of cerebral amyloid pathology. However, the result does not independently exclude Alzheimer’s disease, particularly at an early stage.
An increased p-Tau181/Amyloid beta-42 ratio (>0.068) reflects reduced CSF Amyloid beta-42 and/or increased p-Tau181 and is consistent with an Alzheimer’s disease-related CSF biomarker profile, indicating an increased likelihood of cerebral amyloid pathology.
Note: All results must be interpreted in conjunction with the clinical presentation, cognitive assessment, neuroimaging findings and other available CSF biomarkers. Results close to the decision threshold should be interpreted cautiously, as analytical and biological variation may affect classification.
Important qualification: The 0.068 threshold is a Fujirebio Lumipulse G-specific amyloid-PET concordance cut-off, and results generated on other manufacturers’ instruments are not interchangeable.
Accredited NRL Laboratory
Weekly
Alzheimer's disease (AD) is characterized by two hallmark brain pathologies: Amyloid-beta plaques and intracellular neurofibrillary tangles composed of hyperphosphorylated Tau. These are the most established biomarkers used clinically and in research; an elevated p-Tau181/Amyloid-beta 42 ratio is a strong surrogate marker of amyloid plaque burden, while alow result is a strong indicator that the patient's cognitive decline is not due to AD.
CSF
0.5 mL
Polypropylene tubes
The lumbar puncture should preferably be performed in the morning.
The lumbar puncture should be performed at level L3/L4 or L4/L5.
Discard the first few drops, to avoid blood-stained specimens) and collect CSF in an appropriate polypropylene collection tube.
Rejection criteria: Samples received in tubes other than polypropylene e.g. polystyrene
| Temperature | Period |
|---|---|
| Frozen | 2 months at -20°C |