Test tube with blood sample for Alzheimer disease test
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New Alzheimer’s Blood Tests Are Easy. But Do You Really Want One?
While new blood tests claiming to detect Alzheimer’s before symptoms appear seem promising, they also present significant concerns that patients and doctors must weigh carefully. Promoters of these tests argue they can identify the disease early, but they also prompt critical discussions between healthcare providers and patients, particularly regarding positive results.
A study in JAMA Neurology highlights one issue: even if tests indicate a high risk of cognitive decline, many individuals remain symptom-free five years later despite elevated Alzheimer’s-related proteins. Another JAMA essay notes that some patients might immediately associate a positive test with death.
The Limits Of Tests
It’s important to understand what these tests can and cannot do. They detect biomarkers, specifically p-tau 217 and beta amyloid, linked to Alzheimer’s in the brain. A high level of these proteins suggests a greater risk of developing symptoms later but doesn’t confirm the presence of Alzheimer’s.
These tests are suitable only for individuals with mild cognitive impairment suspected to be early Alzheimer’s. They provide evidence supporting an Alzheimer’s diagnosis rather than another condition but do not address other dementia forms.
This is akin to a high cholesterol test indicating increased heart disease risk without guaranteeing a cardiac event. Predicting Alzheimer’s is even more challenging because many people with high amyloid β levels never show symptoms.
Researchers debate whether individuals with biomarkers but no symptoms have Alzheimer’s. From a patient’s viewpoint, if there are no significant memory or behavior changes, do they really have the disease?
A Rising Risk, But No Certainty
A study led by Rachel Buckley at Mass General Brigham Hospital examined approximately 2,700 people without cognitive decline initially tested for tau protein. About 38% with very high tau levels experienced cognitive impairment after five years, compared to 12% with low levels. This risk was higher for older, less-educated men and increased over a decade.
Despite 38% being a significant risk, it’s not a certainty. The study didn’t consider other medical conditions or determine if Alzheimer’s caused the cognitive impairment.
Not A Death Sentence
A JAMA essay by Stanley Lyndon, Lauren Behlke, and Juan Carlos Urizar highlights ethical issues from early Alzheimer’s diagnoses, even with mild symptoms. Many patients inquire about dying, some consider physician-assisted death or suicide.
The essay references a study where 20% of cognitively normal adults with elevated amyloid-β expressed they would consider PAD if they became impaired, suffered, or burdened others.
The Physician’s Role
Access to simple blood tests for Alzheimer’s proteins is increasing. Previously, few patients were tested due to the invasive and expensive alternatives like spinal taps or PET scans, and the lack of effective treatments.
Now, blood tests for Alzheimer’s proteins might become routine in annual check-ups. Lifestyle changes like improved diet, exercise, and social interaction can enhance cognition, and new drugs might slow progression, albeit with limited benefits. These advancements could raise demand for biomarker tests.
However, as noted by Lyndon and colleagues, these tests may carry an emotional burden. Physicians must guide patients in understanding their results. Discussions should begin even before consenting to a test, covering the predictive limitations and uncertainty of the prognosis, even with a positive result.
Patients need to understand that while results may indicate increased dementia risk, certainty is not assured. No test can fully predict disease progression, and positive results may lead to depression and anxiety.
The authors state, “Biomarkers can clarify pathology, but they cannot write an individual’s timeline. Progression from MCI [mild cognitive impairment] to dementia varies widely; cognitive reserve, mixed pathologies, vascular disease, depression, sleep disorders, medication effects, and social supports shape trajectories. The risk is that patients may turn biological information into temporal certainty, collapsing ambiguity into catastrophic inevitability.”
Post-diagnosis discussions should also address community resources and support for family caregivers. For instance, physicians can bill Medicare for teaching caregiving skills to family members, though it’s not widely practiced.
Previously, I discussed best practices for diagnosing dementia, as recommended by Melissa Armstrong of the University of Florida School of Medicine, emphasizing compassion, empathy, and practical advice.
Early diagnosis is becoming more routine, yet it may increase uncertainty about disease progression and anxiety. In this context, patients and families should ask more questions, and doctors should provide clearer answers.
