Alzheimer's Blood Tests May Give Inaccurate Results in People with Kidney Disease

Alzheimer’s disease is commonly diagnosed through biomarkers—proteins in the blood or spinal fluid that signal early changes in the brain. These include tau, amyloid beta, and neurofilament light chain (NfL) proteins. Yet, because kidneys filter waste from the blood, researchers suspected that impaired kidney function might cause these biomarkers to accumulate, even in the absence of brain disease.

To test this theory, Dr. Francesca Gasparini and her team at the Karolinska Institutet in Sweden tracked 2,279 adults with an average age of 72 who had no signs of dementia at the study’s start. Each participant underwent physical exams, cognitive testing, and blood analysis to measure kidney function alongside Alzheimer’s-related biomarkers. The group was then followed for eight years, with dementia diagnoses recorded over time.

The results revealed a clear pattern. People with weaker kidney function consistently showed higher blood levels of Alzheimer’s biomarkers—especially tau and NfL proteins—compared to those with healthy kidneys. However, when the researchers adjusted for age, sex, and the APOE-e4 gene (a major dementia risk marker), reduced kidney function did not increase the likelihood of developing dementia.

Even so, one group stood out. Individuals who had both kidney impairment and high NfL levels faced nearly twice the risk of developing dementia compared to those with normal kidney function. This suggests that kidney problems may accelerate dementia onset in people already biologically vulnerable.

Researchers concluded that doctors need to check kidney health when interpreting Alzheimer’s blood biomarkers, as poor kidney clearance may inflate test results without reflecting real brain changes. The takeaway: good kidney care may be more vital to brain health—and diagnostic accuracy—than previously appreciated.

REFERENCE: Francesca Gasparini, Martina Valletta, Davide Liborio Vetrano, Giorgi Beridze, Debora Rizzuto, Amaia Calderón-Larrañaga, Claudia Fredolini, Matilda Dale, Bengt Winblad, Laura Fratiglioni, Giulia Grande. Kidney Function, Alzheimer Disease Blood Biomarkers, and Dementia Risk in Community-Dwelling Older Adults. Neurology, 2026; 106 (1) DOI: 10.1212/WNL.0000000000214446