Scientists just need to work out a few challenges — like accessibility and getting doctors on board — first.
Good news for brain health this summer: FDA-approved drugs like Leqembi available for Alzheimer’s are becoming more widely available. The caveat: These drugs only seem to move the dial for people who are very, very early in the course of their journey with Alzheimer’s disease. This need for better diagnostics is driving the quest for the super-simple, super accurate, Alzheimer’s blood test.
Today, lumbar punctures and PET brain scans are the gold standards for diagnosing Alzheimer’s disease. But, experts point out, they’re also invasive, expensive and hard to access. To fill the gap, scientists have been working on developing accurate blood tests. The blood tests measure proteins that serve as proxies of beta-amyloid and tau in the brain. Some tests are commercially available and used in clinical trials. But it isn’t clear how or when they’d make the leap to the doctor’s office or when they’d become a standard part of patient care.
According to Hanna Huber at the University of Gothenburg in Sweden blood tests for Alzheimer’s tests indicate whether a patient with memory issues has the tell-tale pathology for Alzheimer’s flowing around in their bloodstream. If so, she said, it’s an early indication that they could benefit from a disease-modifying anti-amyloid Alzheimer’s drugs.
Huber added that this knowledge also gives clinicians a baseline to help them better monitor the progress of such a treatment: “In response to a disease-modifying drug, these biomarkers begin to normalize,” she told Being Patient.
Challenge 1: Making Alzheimer’s blood tests accessible to all
One of the drawbacks, however, according to Huber, is that blood tests too have their accessibility issues. For example, she explained, they require temperature control and special handling.
“Currently, use of Alzheimer’s blood tests is limited by the need to visit a clinic, administration by trained personnel, and strict time-limited and temperature-dependent delivery and storage procedures,” Huber said in a press release.
In Huber’s recent study, the results of which were presented at AAIC 2023, she and her colleagues wanted to address the accessibility issue surrounding diagnosis. To reduce the amount of travel required for patients and make the process a lot simpler, Huber and her team developed a finger-prick blood test.
They collected blood from 77 memory clinic patients in Barcelona using their test. The blood was then placed onto small cards where the biomarkers of interest would seep in and remain stable. These cards were shipped without any temperature control to the University of Gothenburg in Sweden.
Despite this lack of temperature control, recipients in a processing lab did succeed at quantifying many blood biomarkers of Alzheimer’s including various types of tau protein.
“A method that allows blood collection at home and that is simple enough to be performed independently, or by caregivers, would increase accessibility of these tests,” Huber said. “It would result in improved early diagnosis and better monitoring of patients considered ‘at risk’ or those who are receiving approved therapies.”
Challenge 2: Making blood tests reliable — and getting doctors on board
“Blood tests — once verified and approved — would offer a quick, noninvasive and cost-effective option,” Maria C. Carrillo, Ph.D., Alzheimer’s Association chief science officer said at AAIC 2023. But some clinicians noted that blood tests won’t be the start and finish of an Alzheimer’s diagnosis. There will still be a need for further diagnostic work by specialists.
Sharon Cohen, the medical director and principal investigator at the Toronto Memory Program believes that blood tests may be available to doctors within the next one to two years. However, they will likely be used as screening tools alongside other tests, she said.
“Blood tests will empower clinicians to be more readily involved in early detection of Alzheimer’s disease,” Cohen said. “However, the blood test result itself is a predictive or screening tool only. For those patients who are positive on blood tests, clinicians will then need to refer them for confirmatory tests.”
Dr. Sebastian Palmqvist of the Clinical Memory Research Unit at Lund University also presented the findings of an Alzheimer’s blood test study at AAIC 2023. One of the issues that Palmqvist and colleagues identified is that doctors were hesitant to diagnose their patients with Alzheimer’s, even if the results came back positive.
Palmqvist’s team observed 307 middle-aged and older patients across 17 primary care centers. After a visit with the doctor, cognitive tests, and a preliminary brain scan, the doctors would suggest the diagnosis and course of treatment for patients.
While C2N Diagnostics’ PrecivityAD2 blood test for Alzheimer’s proved accurate in diagnosing the disease 85 percent of the time, doctors reading the results were only confident in the blood test’s diagnosis about 50 percent of the time, Palmqvist told Being Patient.
Going by the doctor’s treatment recommendations, more than half of people in Palmqvist’s study who had Alzheimer’s would not receive treatment.
“Due to the lack of accurate diagnostic tools, it is currently very difficult for primary care doctors to identify Alzheimer’s disease, even among patients with cognitive impairment,” Palmqvist said. “This too often leads to diagnostic uncertainty and inappropriate treatment.”
The bottom line for Palmqvist is that these forthcoming Alzheimer’s blood tests should improve accuracy of people’s diagnoses — and make sure more patients are connected with appropriate treatment, faster.