Two experimental blood tests are showing promise in detecting early signs of Alzheimer's disease, offering a less invasive method for diagnosis. Roche presented data at the 17th Clinical Trials in Alzheimer's Disease congress (CTAD) on these blood tests, which reportedly show "very good accuracy" in ruling out Alzheimer's pathology.
With the number of people living with dementia projected to exceed 152 million by 2050, early and accurate diagnosis of Alzheimer's disease is crucial. Current diagnostic methods often rely on clinical symptoms and invasive biomarker tests. These new blood tests aim to provide a simpler, more accessible alternative.
Elecsys Amyloid Plasma Panel
The Elecsys Amyloid Plasma Panel is a minimally invasive blood test that requires only a small blood sample. According to Margherita Carboni, PhD, Roche Diagnostics Neurology Indication Lead, this test checks levels of pTau 181, a protein that accumulates at increased levels in the blood during the early stages of cognitive impairment. The test also identifies the presence of the ApoE4 gene, a significant genetic risk factor for Alzheimer's disease.
In a study involving 492 participants across the United States and Europe, the Elecsys Amyloid Plasma Panel demonstrated a high negative predictive value (NPV) of 96.2%. This indicates that the test can accurately rule out amyloid pathology, a hallmark of Alzheimer's, as a possible cause of cognitive decline symptoms.
pTau 217 Assay
Roche is also developing a pTau 217 assay as a 'double cutoff' biomarker test. This test aims to minimize the "grey zone" where results are neither clearly positive nor negative. Studies show this assay keeps the grey zone around 12%.
Expert Perspectives
Manisha Santosh Parulekar, MD, chief of the Division of Geriatrics and co-director of the Center for Memory Loss and Brain Health at Hackensack Meridian Neuroscience Institute, noted that prior research has shown elevated pTau 181 levels in individuals with Alzheimer's disease. She added that individuals with one copy of the ApoE4 gene have a three-fold increased risk of developing Alzheimer's, while those with two copies have a 12-fold increased risk. These assays may offer a less invasive and more accessible method for diagnosing Alzheimer's disease.
Clifford Segil, DO, a neurologist at Providence Saint John's Health Center, expressed caution, noting that blood tests are not typically what clinical neurologists rely on. He suggested that a series of tests administered by primary care physicians or allied healthcare professionals might be more beneficial for widespread screening.
Segil also advised that individuals identified by these tests should receive anti-amyloid medications to determine if treatment leads to any discernible change in their memory loss. He expressed concern that the clinical utility of amyloid tests may decrease if postmarketing surveillance of anti-amyloid medications does not show significant improvement in patients' cognitive complaints.
