Phosphorylated Tau Blood Test Shows Promise for Alzheimer’s and Amyloidosis Diagnosis

Recent research indicates that measuring levels of phosphorylated tau (p-tau) in the blood may offer a valuable diagnostic tool, not only for Alzheimer’s disease but also for various forms of amyloidosis. This advancement could lead to earlier and more accurate diagnoses for both conditions, improving patient outcomes.

Alzheimer’s Disease and p-tau

Elevated levels of p-tau in the blood have long been recognized as a potential biomarker for Alzheimer’s disease. Studies, including research published in Nature Medicine (Petersen et al., 2026), suggest that a single blood test measuring p-tau217 can help predict the onset of Alzheimer’s symptoms. A study reported in Nature (Aarsland et al., 2025) highlights the prevalence of Alzheimer’s disease pathology using blood p-tau217 measurements.

Beyond Alzheimer’s: Amyloidosis Detection

New findings reveal that elevated p-tau levels aren’t exclusive to Alzheimer’s. Research published in Nature (via duckduckgo) demonstrates that serum p-tau can also serve as a biomarker for systemic amyloidosis, including transthyretin (ATTR) amyloidosis and immunoglobulin light chain (AL) amyloidosis. This is particularly significant because these conditions can cause polyneuropathy (PNP), and distinguishing amyloidosis-related PNP from other causes can be challenging.

Understanding Amyloidosis

Amyloidosis occurs when abnormal proteins build up in tissues and organs. ATTR amyloidosis, caused by misfolded transthyretin protein, affects individuals over 65 (Ruberg & Maurer, 2024). AL amyloidosis involves the buildup of abnormal immunoglobulin light chains. The study found that p-tau181 levels were higher in individuals with AL and ATTR amyloidosis compared to controls, and were more pronounced in those with polyneuropathy.

Key Findings on p-tau Levels

• Higher serum p-tau181 levels were observed in individuals with AL and ATTR amyloidosis compared to healthy controls.
• The increase in p-tau levels was more significant in patients experiencing polyneuropathy.
• AL amyloidosis showed a more pronounced effect on p-tau levels than ATTR amyloidosis.
• Presymptomatic ATTR amyloidosis patients exhibited increasing p-tau181 levels as they approached predicted symptom onset.
• Measurements of p-tau217 showed similar increases and diagnostic potential as p-tau181.

Implications for Diagnosis

The ability to detect amyloidosis using a blood test for p-tau could significantly improve diagnostic accuracy and speed. Currently, diagnosis often relies on tissue biopsies, which are invasive and can be challenging to obtain. A blood test offers a less invasive alternative.

Future Directions

Further research is needed to fully understand the relationship between p-tau levels and amyloidosis, and to establish standardized testing protocols. However, these findings represent a promising step towards earlier and more accurate diagnosis of both Alzheimer’s disease and amyloidosis, potentially leading to more effective treatments and improved patient care.

Frequently Asked Questions (FAQ)

What is phosphorylated tau? Phosphorylated tau is a protein that accumulates in the brain in Alzheimer’s disease and other neurodegenerative conditions. Measuring its levels in blood and cerebrospinal fluid can help track disease progression.

What is amyloidosis? Amyloidosis is a group of diseases caused by the buildup of abnormal proteins in organs and tissues.

Is a p-tau blood test currently available? Whereas research is promising, p-tau blood tests are not yet widely available for routine clinical use. They are primarily used in research settings.

Sources:

• Petersen, K. K. Et al. Predicting onset of symptomatic Alzheimer’s disease with plasma p-tau217 clocks. Nat. Med. https://doi.org/10.1038/s41591-026-04206-y (2026).
• Aarsland, D. Et al. Prevalence of Alzheimer’s disease pathology in the community. Nature 650, 182–186 (2025).
• Ruberg, F. L. & Maurer, M. S. Cardiac amyloidosis due to transthyretin protein: a review. JAMA 331, 778–791 (2024).
• Kaeser, S. A. Et al. Blood phosphorylated tau elevation as a biomarker in immunoglobulin light chain and transthyretin amyloidosis. Nat. https://doi.org/10.1038/s41591-026-04272-2 (2026).