Phospho‑Tau/Total‑Tau/A Beta42, CSF (Change effective as of 05/20/24: Refer to 3017653 in the May Hotline)
Also known as: PHOSPHO T
Use
Measures cerebrospinal fluid biomarkers—phospho‑Tau (181), total‑Tau, and Aβ42—to calculate ratios (pTau181/Aβ42 and tTau/Aβ42) that align more closely with amyloid PET imaging and aid evaluation of Alzheimer’s disease and cognitive impairment in adults ≥55 years old. Interpretation should always be in context with clinical diagnostic evaluation and not used alone to establish diagnosis.
Special Instructions
Change effective as of May 20, 2024: Test relocated to Alzheimer’s Disease Markers, CSF (ARUP test 3017653) per May Hotline. Providers should refer to that test going forward.
Limitations
Failure to adhere to collection instructions, especially using inappropriate tubes (e.g., polystyrene), may result in falsely reduced Aβ42 concentrations and consequently elevated ratio values. The ratios are not validated for predicting dementia development or monitoring therapy response, and results should not be used alone to establish Alzheimer’s disease diagnosis.
Methodology
Immunoassay (ECLIA)
Biomarkers
Result Turnaround Time
1-7 days
Related Documents
For more information, please review the documents below
Specimen
Cerebrospinal Fluid
Volume
Not provided
Minimum Volume
Not provided
Collection Instructions
Perform lumbar puncture and discard first 1–2 ml of CSF; collect directly into low‑bind polypropylene false‑bottom CSF tube (ARUP Supply #58810 preferred). Avoid syringes/extension tubing. Fill ≥50% of tube. Freeze or refrigerate and send in original tube; do not refreeze refrigerated or thaw frozen specimens.
Causes for Rejection
Specimen types other than listed; hemolyzed CSF; use of polystyrene tubes; refrozen or thawed specimens
Stability Requirements
| Temperature | Period |
|---|---|
| Refrigerated | 14 Days |
| Frozen | 8 weeks |
Other tests from different labs that may be relevant