Key Points

The test could allow for more accurate and faster PSP diagnosis than current methods, said the team from the University Health Network (UHN) and the University of Toronto.

"This assay is important for assigning patients to the correct clinical trials, but it will be even more important in the future as researchers develop targeted, precision treatments for PSP," said Ivan Martinez-Valbuena, a scientific associate at the Rossy Progressive Supranuclear Palsy Centre at the UHN.

"We need diagnostic tools to be developed hand-in-hand with new treatments so that as these treatments become available, we can identify the patients who would benefit most," she added.

While researchers have successfully detected misfolded proteins in neurodegenerative diseases, the technique has not always been accessible, and some patients are unable to undergo the procedure.

As a result, patients are typically diagnosed based on their symptoms and clinical presentation, so some patients may be misdiagnosed -- particularly for rarer neurodegenerative diseases such as PSP. This could also have a negative impact on research since patients with PSP may be misdiagnosed with Parkinson's disease and be included in a trial that targets the wrong protein, influencing the results.

The new test, described in a recent issue of JAMA Neurology, can detect a sequence of misfolded tau specific to PSP.

The results showed that "disease-associated tau protein can be detected in the skin in living patients with high accuracy," said Gabor Kovacs, professor of laboratory medicine and pathobiology at Toronto University's Temerty Faculty of Medicine.

Further, examining skin biopsies of patients with PSP as well as people with multiple system atrophy, corticobasal degeneration, Parkinson's disease, and healthy controls, the team found misfolded tau in most patients with PSP, but much less frequently in other neurodegenerative diseases.

Importantly, the misfolded tau protein was not detected in patients with Parkinson's disease or the healthy controls. Overall, the researchers found the assay had 90 per cent sensitivity and 90 per cent specificity.

Martinez-Valbuena said the test could be incorporated into a panel of blood- and skin-based tests, along with clinical information, to help clinicians make more precise diagnoses and recommend more appropriate clinical trials.

- IANS