Plasma phosphorylated (p)-tau217 testing can help identify preclinical Alzheimer's disease (AD), which could aid clinical trial recruitment.
Recruiting preclinical AD participants for clinical research is challenging owing to a lack of symptoms and the high cost and invasiveness of cerebrospinal fluid (CSF) tests and brain amyloid PET imaging.
Plasma p-tau217 has consistently shown high performance in detecting AD pathology in patients with mild cognitive impairment and dementia, but there has been concern that it may have lower accuracy in cognitively unimpaired adults, said lead investigator Gemma Salvadó, PhD, with the Clinical Memory Research Unit, Lund University, Sweden.
However, "our study shows that plasma p-tau217, alone or in combination with invasive tests, can be used accurately to assess amyloid-positivity in cognitively unimpaired participants, to streamline the inclusion of these participants in preventive clinical trials," she told Medscape Medical News.
The findings were presented on July 28 at the Alzheimer's Association International Conference (AAIC) 2024.
Correlation to CSF, PET Amyloid Status
The investigators assessed the clinical accuracy of plasma p-tau217 as a prescreening method in 2917 cognitively unimpaired adults (mean age, 67 years; 57% women) across 12 independent cohorts who had available plasma p-tau217 and amyloid beta PET imaging or CSF samples.
They found that plasma p-tau217 levels correlated with amyloid beta CSF status and PET load.
As a standalone test, plasma p-tau217 identified amyloid beta PET–positive cognitively normal adults with a positive predictive value of 80% or greater.
The positive predictive value increased to 95% or greater when amyloid beta CSF or PET was used to confirm a positive plasma p-tau217 result.
As a first step, plasma p-tau217 could significantly reduce the number of invasive tests performed because only individuals with a positive p-tau217 test would go on to PET imaging or CSF sampling, Salvadó told conference attendees. This may reduce trial recruitment costs and get more patients enrolled.
Although the study had a large sample size, "these results should be replicated in independent studies, [in] more heterogenous participants, and coming from the clinical setting instead of observational studies to avoid possible bias," Salvadó added.
A New Diagnostic Era
Commenting on the research for Medscape Medical News, Heather Snyder, PhD, vice president of medical and scientific relations at the Alzheimer's Association, said what's particularly interesting about this study is that the researchers examined multiple cohorts of cognitively unimpaired individuals and "consistently" found that plasma p-tau217 could identify individuals with amyloid-positive PET and CSF with high accuracy.
"This may reduce the need for more expensive and more invasive scans or lumbar punctures to confirm if an individual has the biology," Snyder said.
"Blood tests are revolutionizing Alzheimer's detection, diagnosis and ultimately treatment," Howard Fillit, MD, co-founder and chief science officer of the Alzheimer's Drug Discovery Foundation, added in a statement sent to Medscape Medical News.
He predicted that blood tests will "soon replace more invasive and costly PET scans as the standard of care and serve as the first line of defense in diagnosing the disease."
"After many years of research, the field is in a place where we have novel biomarkers and diagnostics to support a diagnosis," the way cholesterol is used to help detect heart disease, said Fillit.
"The diagnostic framework for Alzheimer's — an incredibly complex disease — is constantly evolving. As we usher in the new era of care, we are moving closer to the day when blood tests will be complemented by digital tools to provide precise and timely diagnoses and risk assessments backed by numerous data points, complementing existing cognitive tests," he added.
Note: This article originally appeared on Medscape.
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