For years, Alzheimer’s disease could only be diagnosed after symptoms had already taken hold. By then, much of the damage - memory loss, confusion, and cognitive decline – was irreversible, leaving patients virtually hopeless. Today, new breakthroughs offer new hope for early diagnosis.
Researchers now know that Alzheimer’s begins with silent, biological changes in the brain, over a decade before symptoms appear. These changes include amyloid buildup—a type of plaque that accumulates between nerve cells—and tau tangles, stringy proteins that are toxic to the neurons in brain cells. The challenge has been finding simple, reliable ways to detect these changes early enough to intervene.
Fortunately, recent advances in blood-based biomarkers, especially phosphorylated tau (p-tau) blood tests, represent a turning point. For the first time, it’s becoming possible to identify people at risk long before Alzheimer’s takes hold.
Early Detection Matters
As with all diseases, early detection of Alzheimer’s is the key to prevention and treatment. The ability to spot Alzheimer’s five or more years before symptom onset would allow doctors to begin treatment before irreversible damage occurs. Drugs like Leqembi and Kisunla, which can modify the disease, tend to work best at the earliest stages of Alzheimer’s when brain cells are still largely intact. Patients could also be enrolled in prevention-focused clinical trials, most of which focus on early-stage disease. And doctors could encourage lifestyle changes in exercise, diet, sleep and blood pressure control that can slow the disease’s progression.
Until recently, though, the only reliable way to confirm Alzheimer’s pathology was through expensive, invasive tests – PET scans or spinal fluid analysis—that are unavailable to most people.
That’s changing fast.
The Rise of Blood Biomarkers
Making early detection far more practical, a new class of blood-based biomarker tests closely mirror what PET scans and spinal fluid tests reveal, but years before symptoms appear. The tests measure proteins associated with Alzheimer’s pathology, especially beta-amyloid (Aβ) and phosphorylated tau (p-tau).
In multiple studies, elevated levels of these proteins in blood are strongly predictive of future Alzheimer’s. Importantly, these tests are not simply diagnostic—they can signal early brain changes and help determine whether further imaging or monitoring is needed.
Quest Diagnostics’ AD-Detect: A New Tool for the Clinic
Quest Diagnostics is leading the way in bringing these discoveries to doctor’s offices. The company’s AD-Detect™ test measures both the Aβ42/40 ratio and p-tau217 levels, generating an “AD-Detect Likelihood Score” that reflects the probability of Alzheimer’s-type changes in the brain.
Quest is also planning to market a new test—the Fujirebio plasma p-tau217/Aβ ratio test—that will be the first FDA-cleared blood test designed to evaluate adults showing early cognitive symptoms.
These tests have yet to be approved for broad population screening. But they represent critical movement toward a future in which Alzheimer’s risk can be measured through a simple blood draw, much like cholesterol or glucose levels today.
The Road Ahead: A Blended Strategy
We still don’t have a single test that can predict Alzheimer’s with certainty. The best strategy for early detection employs a blended approach with multiple tools:
Risk Profiling: Assessing genetic and lifestyle factors (like APOE4 status, family history, and cardiovascular health).
Blood Testing: Blood biomarker measurements (Aβ42/40, p-tau217).
Longitudinal Tracking: Monitoring changes by repeating tests every 1–3 years.
Follow-up Imaging: Using PET scans or spinal fluid testing to confirm results.
Lifestyle Changes: Adopting lifestyle changes—exercise, healthy diet, quality sleep—proven to protect brain health.
With strong partnership between patients, physicians, and lab tools like AD-Detect, this multi-layered strategy is our current best hope for broadscale early detection.
The Bottom Line
For the first time, we’re approaching a time when Alzheimer’s disease can be detected years before memory loss begins. Blood-based biomarkers—especially p-tau217—are leading the charge, transforming early detection from a research concept into a clinical reality.
While more validation is needed, the momentum is unmistakable. As tests like Quest’s AD-Detect expand into practice, patients and doctors will gain a crucial new window of time—years, not months—to act.
Alzheimer’s still begins quietly. But now, we’re learning to listen.