PET Scan Imaging Is Crucial for Diagnosing Alzheimer’s Disease

Eliminating barriers to access is key to more timely and accurate diagnosis 

There is no single test consistently used to diagnose Alzheimer’s disease, and today there is often no diagnosis, an incorrect diagnosis, or a very late diagnosis. Alzheimer’s is a fatal, debilitating disease that robs an individual of who they are, and the web of the disease extends much further, burdening loved ones with gut-wrenching decisions and financial costs. 

It’s also one of the most prevalent diseases: more than six million Americans are living with Alzheimer’s dementia, while another five million are undiagnosed. Inconsistent methods of diagnosis lead to a larger impact on both the effort to find a cure, including limitations on clinical trial participation, and on whether a person may be eligible to take advantage of opportunities to slow the progression of the disease with current treatments.  

Alzheimer’s disease is especially common among women and communities of color, who are more likely to experience the symptoms of Alzheimer’s—including memory loss, confusion, and difficulty concentrating—but who lack a formal diagnosis. Compared to non-Hispanic Whites, Black Americans are twice as likely to develop the disease. UsAgainstAlzheimer’s projects that on our present course nearly 40 percent of Americans living with Alzheimer’s will be Black or Latino by 2030. Diagnosis among minority groups is also delayed, with fewer people diagnosed in the earlier stages of the disease.   

Right now, a reliable Alzheimer’s diagnosis cannot be made by clinical assessment alone. The good news is that there are tests that can identify the underlying pathology of Alzheimer’s Disease. The problem is that these tests are not always available or reimbursed by Medicare or other insurance.  

Positron emission tomography (PET) radiotracers are the only FDA-approved tests to identify patients with the two hallmark pathologies of the disease: amyloid plaques and aggregated tau neurofibrillary tangles. In Alzheimer’s disease, amyloid plaques can begin accumulating in the brain up to 20 years prior to the onset of symptoms¹. The availability of these two novel diagnostics can assist clinicians in making a diagnosis for their patients who are suffering from symptoms of cognitive decline. Now that there are amyloid targeted disease-modifying treatments available, it’s even more critical that physicians have access to these types of diagnostic tools to help identify the right patients who may benefit from these types of therapies.  

One large U.S. study (IDEAS) found that nearly 36% of people diagnosed with Alzheimer’s disease by dementia specialists had no evidence of amyloid plaques on PET scans of their brains. And, about half of patients (52%) seeing dementia specialists, but not diagnosed with Alzheimer’s, had amyloid in their brains. The IDEAS study also showed that an amyloid PET scan changed how physicians managed patients in more than 60 percent of cases, whether they had mild cognitive impairment or dementia².  

Unfortunately, barriers in the Medicare payment and reimbursement system are compromising patient access to these precision diagnostics, and potentially disease-modifying treatments. A Government Accountability Office report highlighted how these policies limit recruitment of ethnically and clinically diverse patient groups in Alzheimer’s disease research. The report states: “According to the organizers of the IDEAS Study, as of November 2020, four of the six hospitals initially invited to participate in the study have declined to do so. The study organizers said that those hospitals, which had all participated in the original IDEAS Study, declined to participate because the packaged payment would cause them to incur a financial loss for each procedure performed. This may pose a challenge because, according to the study organizers, hospitals associated with academic institutions have much of the expertise in recruiting ethnically and clinically diverse groups into such trials.”  

In an essay for STAT News, Jim Taylor, a retired financial analyst, described the “gnawing uncertainty” as he watched his wife, Geri, show signs of the disease for two years before doctors were able to confirm she had it. He wrote: “Had Geri not entered [a] clinical trial and received [a] critical amyloid PET scan, we might still not have a definitive diagnosis…While an Alzheimer’s diagnosis is never easy, she and I no longer have to struggle with uncertainty about her disease.” 

For more than 30 years, Lilly’s scientists have been working to develop treatments for Alzheimer’s. We want to make sure future breakthroughs are available to anyone who could benefit. We urge the Centers for Medicare & Medicaid Services to consider changes to existing coverage and payment policies for PET scans that enable early and accurate diagnosis and provide physicians the diagnostic information they need to identify appropriate patients for amyloid-targeted disease-modifying therapies. 

^{1 Villemagne. Amyloid β deposition, neurodegeneration, and cognitive decline in sporadic Alzheimer's disease: a prospective cohort study. The Lancet Neurology. April 2013} 

^{2 Rabinovici GD, Gatsonis C, Apgar C, et al., “Association of Amyloid Positron Emission Tomography With Subsequent Change in Clinical Management Among Medicare Beneficiaries With Mild Cognitive Impairment or Dementia,” Journal of the American Medical Association 2019;321(13): 1286-1294: https://jamanetwork.com/journals/jama/fullarticle/2729371.}