Blood Test for Alzheimer’s May Also Indicate Heart and Kidney Disease

Blood tests for Alzheimer’s disease are rapidly transforming how clinicians diagnose the condition. However, some scientists caution that the meaning of a positive blood test is not yet fully understood. Recent research suggests that elevated levels of phosphorylated tau protein (pTau), a biomarker for Alzheimer’s, may also indicate the presence of systemic amyloidosis, a group of disorders affecting the heart, and kidneys.

Phosphorylated Tau (pTau) as a Potential Biomarker for Systemic Amyloidoses

Researchers at the German Center for Neurodegenerative Diseases (DZNE) and the Hertie Institute for Clinical Brain Research (HIH) at the University of Tübingen have discovered that elevated pTau levels are also present in two common forms of systemic amyloidosis: immunoglobulin light chain amyloidosis (AL) and transthyretin amyloidosis (ATTR). These findings, published in Nature Medicine on March 11, 2026, could lead to improved diagnostic approaches for both Alzheimer’s disease and these lesser-known conditions.

Systemic amyloidosis occurs when misfolded proteins, known as amyloids, accumulate in organs like the heart and kidneys. While amyloid deposits in Alzheimer’s disease form in the brain, the Tübingen researchers observed a similar elevation of pTau in the blood of patients with both central and peripheral amyloidosis.

Study Details and Findings

The study analyzed serum samples from 280 individuals across Germany, Italy, and the Netherlands. The cohort included:

• 97 people with immunoglobulin light chain amyloidosis (AL)
• 52 people with hereditary transthyretin amyloidosis (ATTR)
• 30 people with sporadic transthyretin amyloidosis (ATTR)
• 30 people with polyneuropathy not caused by amyloidosis
• 71 healthy, age-matched controls

Results showed that individuals with AL or ATTR had significantly higher serum p-tau181 levels compared to controls. AL elevated p-tau181 more than ATTR. P-tau181 levels tended to be higher in individuals with polyneuropathy, likely indicating more advanced disease. Serum p-tau217 levels were also significantly elevated in patients with AL and ATTR, and showed better discrimination of ATTR than p-tau181.

the markers flagged systemic amyloidoses with an accuracy of 82 percent for p-tau181 and 77 percent for p-tau217.

Implications for Diagnosis

“Our results underscore that high pTau levels in blood are not specific to Alzheimer’s, but can also occur in other amyloid diseases,” says Mathias Jucker, professor and scientist at DZNE and HIH. “Our results could open up new possibilities for diagnosis of systemic amyloidosis. The blood marker pTau can be measured relatively easily and may facilitate earlier detection and help confirm or rule out suspected cases.”

Since pTau levels are similar in both Alzheimer’s and systemic amyloidosis, researchers suggest that measuring the size of pTau fragments may help differentiate between the two conditions. Peripheral neurons produce a larger version of the protein than those in the brain, and assays for “brain-derived” tau are currently under development.

Further Research

Ongoing research focuses on developing assays to specifically detect brain-derived tau, which could improve the accuracy of Alzheimer’s diagnosis and reduce the risk of misdiagnosis due to systemic amyloidosis.