Alzheimer's is a slow-moving neurodegenerative disease. Decades can pass before clinical symptoms appear, and even when they do it's challenging to identify the disease in patients with mild cognitive impairment.
Clinicians currently lack a clear diagnostic tool to detect Alzheimer's. The disease is generally only formally diagnosed using cognitive or psychological measures, however, in some cases, advanced medical imaging can be used to detect certain pathological characteristics in the brain.
A wide array of potential diagnostic test are currently in various stages of development. Eye scans, blood tests, smartphone pupil tracking apps, and sniff tests have all been proposed to catch the disease before symptoms appear.
Now, in a new study published in Frontiers in Aging Neuroscience, researchers have proposed urine tests as a potential way to detect the disease. The researchers suggest formic acid levels in urine could be a useful early-stage biomarker for Alzheimer's.
Formic acid is a metabolic product of formaldehyde, a molecule that is toxic in high concentrations but also found in low levels in a healthy brain. Recent research has found endogenous formaldehyde may play a role in learning and memory, but high concentrations in the brain can result in cognitive deficits that resemble what is seen in Alzheimer's disease (AD).
To explore the hypothesis that formic acid concentrations in urine can be a biomarker of Alzheimer's disease, the researchers recruited almost 600 subjects at various stages of cognitive decline. The cohort was divided into five groups, from a cognitively healthy group to a group with clinically diagnosed Alzheimer's.
Overall, the researchers found formic acid concentrations were measurably higher in all four cognitively impaired groups compared to the healthy control. The study also found formic acid levels correlated with declining scores on psychological tests measuring cognition.
When the researchers added blood tests for Alzheimer's biomarkers to the mix, they found the diagnostic accuracy increased further, allowing for predictions of disease staging.
It is important to note this is just preliminary research, so lots more work will be needed to validate these findings before a clinical urine test becomes commonly available. Nevertheless, the promising findings point to not only a very simple early screening test for Alzheimer's but also provides clues to a novel degenerative mechanism at play in the disease.
"Using these urine biomarkers can significantly promote the popularity of early screening for AD, which can improve advice on diagnosis, treatment, and lifestyle for people at risk for AD," the researchers conclude. "In-depth research on these biomarkers will also help to explore the mechanisms and potential treatments of AD. Dynamic changes in urinary formaldehyde and urinary formic acid suggest another new metabolic disorder in AD pathogenesis."
The new study was published in the journal Frontiers in Aging Neuroscience.