Alzheimer’s blood test may replace invasive spinal taps for diagnosis

Alzheimer’s disease is not an easy one to diagnose, with physicians relying on expensive PET scans and fluid sampling to make a decision on a patient’s wellbeing. Some exciting advances are being made when it comes to blood-testing, however, that could change the game by offering clearer insights into the disease during its earlier stages. The latest example of this offers a particularly promising pathway forward, with an ability to spot a traditionally hard-to-detect protein called tau, considered a key biomarker of the disease. Tau and another toxic protein called amyloid are seen as two major culprits in the neurodegenerative damage associated with dementia and Alzheimer’s disease. Many of the experimental blood tests under development focus on measuring amyloid levels, with one paper published last year describing a way of revealing misfolding amyloid proteins as a way of detecting Alzheimer’s cases around eight years before clinical symptoms appeared. That research group had a secondary layer to their novel diagnostic method, combining this blood test with a second test to measure tau proteins in the cerebrospinal fluid, which is currently the only way to quantify its levels, though is expensive and invasive.

The new blood test developed by an international research team led by scientists at the University of California, San Francisco, brings tau into the blood-testing fold. The study involved more than 400 participants, some who had been diagnosed with Alzheimer’s, some with mild cognitive impairment and different types of dementia, along with a group of healthy subjects.

By measuring levels of a protein called phosphorylated tau 181 (pTau181), the team found it was able to distinguish those with Alzheimer’s from those in the healthy group, as it presented as 3.5 times higher. The subjects with frontotemporal dementia exhibited the same pTau181 levels as the healthy group. This is significant, as frontotemporal dementia is often misdiagnosed as Alzheimer’s disease.

The team also compared the pTau181 readings obtained through the blood tests with those gleaned from the traditional spinal fluid test, and found that the results mirrored one another. The researchers are now working to improve the blood test, and are hopeful of seeing it in doctor’s offices within five years.