Neurology Central

Ask the experts: should we screen for Alzheimer’s disease? (Part 1: Introduction)


Welcome to the new Neurology Central ‘Ask the experts’ column, with Ellen Clarke, Commissioning Editor at Future Science Group (London, UK). This ‘Ask the experts’, with Maria Carrillo (Alzheimer’s Association), Linda Nazarko (London North West Healthcare NHS Trust, UK), Gabriel Vargas (Amgen, CA, USA) & Henrik Zetterberg (University of Gothenburg, Sweden) will be focusing in on the often controversial topic of screening for Alzheimer’s disease. Over the next couple of days we will cover everything from the need for early diagnosis to the pros and cons of screening, as well current and future therapeutics and diagnostic approaches. You can find out more about the panelists at the bottom of this post.

How common is undiagnosed Alzheimer’s disease?

Carrillo: Only about 50% of an estimated 5.2 million Americans living with Alzheimer’s disease (AD) and other dementias are diagnosed with dementia by a physician. The data behind this comes from the U.S. Census Bureau and the Chicago Healthy Aging Project (CHAP), where everyone in the study is tested for dementia. In contrast, the Alzheimer’s Association estimates that only 50% of individuals in the community that meet the diagnostic criteria for dementia are diagnosed.

To further illustrate the complexity of this issue, the Alzheimer’s Association released a special report that showed those who have a diagnosis of Alzheimer’s or another dementia (including the person’s proxy) are told of their diagnosis less than 50% of the time by their healthcare provider. In previous studies, disclosure rates varied between 36% and 96% from providers that disclose an individual has dementia. In contrast, the same report reveals that 93% of Medicare beneficiaries that have the four most common types of cancer are told of their diagnosis. Not disclosing a diagnosis is mired in complex issues such as diagnostic uncertainty, lack of time and support for a physician to give a diagnosis, concerns about emotional distress, the challenge in communicating the diagnosis, requests by caregivers or the individual themselves not to be told, as well as the inability to provide treatments that can change the course of the disease.

AD is not an easy disease to diagnose because there is no single test to determine if a person has the disease. However, a dementia expert can have a high degree of probability in providing an accurate diagnosis through a comprehensive medical evaluation. At the same time, a primary care physician may not have adequate training to assess an individual or may not want to make the diagnosis. This is only part of the reason people go undiagnosed; other individuals involved in this process, caregivers, healthcare providers, and even a physician, can be reluctant to want to know, or in the latter case, provide a diagnosis of AD.

At what stage in the disease is AD typically diagnosed?

Carrillo: The stage in which Alzheimer’s or other dementias are diagnosed varies significantly, but it is almost always late in the disease process. Determining the stage of the disease at diagnosis is complicated because – as data from surveying caregivers indicates – in some cases, it was more than two years after the initial physician visit that a diagnosis was delivered.

Zetterberg: This depends on the criteria used. Old criteria allowed for making a diagnosis only when the patient’s brain was so severely affected by the disease process that the patient expressed the full dementia syndrome, whereas new criteria allow for making a diagnosis in the mild cognitive impairment stage of the disease, if there is biomarker evidence of AD pathology.

How important is early detection?

Carrillo: Early and accurate detection of cognitive decline is vitally important for helping individuals, caregivers, and families cope with AD. The Alzheimer’s Association believes there are numerous reasons for the value of early detection and diagnosis including:

  1. Provides individuals that opportunity to obtain access to quality care, medical treatments and support services that help maintain independence for as long as possible.
  1. Allows individuals to participate in decisions about their medical care, including providing informed consent for current and future treatment plans.
  1. Provides the individual time to plan for the future and take part in decisions about transportation, safety, financial and legal matters.
  1. Offers individuals and their families and caregivers the chance to seek support, information and community resources; gives the family time to build a care team and tools needed to better handle the challenges of being caregivers.
  1. Allows affected persons to decide if they want to participate in clinical drug trials that advance research, including trials testing experimental therapies that may slow or halt disease progression.
  1. Informs individuals and family members of the reason for the symptoms – this can remove the anxiety and uncertainty about the symptoms they have observed and provide an opportunity to develop an action plan. Lack of a diagnosis makes management of Alzheimer’s even more difficult.
  1. Documentation of a dementia diagnosis in an individual’s medical record may improve care by informing all providers, including those that may be managing comorbidities, that treatment and care should be adjusted to accommodate the cognitive impairment. A survey of Medicare beneficiaries found that among patients with dementia, 26% had coronary heart disease, 23% had diabetes and 13% had cancer.
  1. In some cases, the cause of cognitive impairment is reversible such as depression, delirium, medication side effects, thyroid problems, vitamin deficiencies and excessive use of alcohol. In these cases, the ability to rule out a diagnosis of Alzheimer’s could lead to a diagnosis of a more treatable condition and decrease inappropriate use of medications that could be potentially harmful. One meta-analysis reported that 9% of people with dementia-like symptoms did in fact not have dementia but had other conditions that were potentially reversible.

Nazarko: That’s a question that is being debated in clinical circles. Some argue that it is a ‘diagnosis of despair’ as there are few treatment options. My view is that if we can diagnose early then we can ascertain the wishes of the person with dementia and do our utmost to honor them later when the person is no longer able to express a view.

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