New blood tests for Alzheimer’s are easy. But do you really want one?

The limits of testing

Be aware of what these tests can and cannot do. They are looking for biomarkers, the presence of material in the brain associated with Alzheimer’s disease, called p-tau 217 and beta amyloid.

In other words, they can show that someone has a high level of one or both of these proteins. Does this mean they have Alzheimer’s? Not exactly. Instead, it means they have a higher risk of developing symptoms of the disease at some point in the future

Also remember that these tests are only suitable for people with mild cognitive impairment who a doctor suspects may have early Alzheimer’s disease. For these patients, they may provide valuable evidence that their symptoms are indeed caused by Alzheimer’s disease and not by some other condition. They say nothing about other forms of dementia.

It’s a little, though not quite, like a blood test that shows you have it high cholesterol. This puts you at greater risk for heart disease. But that doesn’t mean you’ll inevitably have a heart attack.

With Alzheimer’s, predicting the future is even murkier. This is because while everyone with advanced disease has high levels of amyloid β in their brain, many people with a lot of these proteins will never have symptoms.

Research scientists debate endlessly whether this means that people with biomarkers but no symptoms have Alzheimer’s disease or not. But from a patient’s perspective, if your memory, executive function, and other behavior never change significantly, do you have Alzheimer’s?

A growing risk, but not a certainty

A new study by Rachel Buckley of Mass General Brigham Hospital and several colleagues looked at the results over several years for about 2,700 people without cognitive impairment when they were first tested for tau protein. The result: About 38 percent of those with very high tau levels experienced cognitive decline after five years, compared with 12 percent for those with low levels. The odds were higher for older men with less education. And they increased over a period of 10 years.

For context, 38% is very high risk. But less than four out of ten is far from certain. Also note that this study did not adjust for participants who may have had other medical conditions. Nor did it look at whether the cognitive decline was due to Alzheimer’s or some other cause.

No death penalty

And there it is a new JAMA essay by Drs Stanley Lyndon, Lauren Behlke and Juan Carlos Urizar It raises important questions about the ethical issues that arise when a patient receives an early diagnosis of Alzheimer’s, especially when they have only mild symptoms.

It seems that many patients respond to their early diagnosis by asking about death. Some want to learn about death with the help of a doctor. Others consider suicide.

The authors cite a study where “20% of cognitively normal adults with elevated amyloid-β reported that they would pursue PAD if they were cognitively impaired, suffering, or burdening others.”

The Role of Physicians

This issue will become especially important as more people have access to simple blood tests for these proteins associated with Alzheimer’s disease. Until recently, relatively few patients were screened because the only alternatives were invasive spinal taps or expensive PET scans. After all, there were by no means effective medical treatments for Alzheimer’s.

Now, we are approaching the time when a blood test for Alzheimer’s-related proteins can be included in the routine labs we do with our annual exams. We have learned interventions such as Better nutrition, exercise and social interaction can improve cognitive function. And new drugs may also delay progression, although their benefits remain limited. All these developments are likely to increase the demand for biomarker testing.

But as Lyndon and his colleagues write, there can be a big emotional cost to these tests. How should doctors help patients understand them and their effects? Importantly, Lyndon and the authors say doctors should start a conversation even before the patient consents to a test.

This conversation should include information about their prognostic boundaries, including how uncertain the prognosis is for any given patient, even if they test positive for high levels of Alzheimer’s-related proteins.

It is critical for patients to understand that the results may indicate a higher risk of future dementia, but not a certainty. No test alone can predict how the disease may develop. And doctors should also tell patients that a positive test can itself put them at risk for depression and anxiety.

As the authors say, “biomarkers can elucidate pathology, but they cannot write a person’s timeline. Progress from MCI [mild cognitive impairment] in dementia varies widely. cognitive reserve, comorbidities, vascular disease, depression, sleep disorders, medication effects, and social supports shape the trajectories. The danger is that patients may transform biological information into temporal certainty, collapsing ambiguity into catastrophic inevitability.”

Any post-diagnosis discussion should also include information about community resources that patients can tap into, as well as support and skills training for family caregivers.

For example, doctors can now bill Medicare for teaching caregiving skills to family members, although few do.

A few years ago, I wrote about best practices for doctors when diagnosing dementia, which were recommended by University of Florida School of Medicine neurologist Melissa Armstrong. It included a powerful combination of compassion, empathy and practical advice.

Early diagnosis is becoming more common. However, this tool can only add to the lack of certainty of how any one person’s disease will progress, as well as increase anxiety. In this environment, it will be up to patients and their families to ask more questions and doctors to have better answers.