Integrating Blood-Based Biomarkers as a Revised Approach to Diagnosing Alzheimer Disease

Maria Carrillo, PhD

In Alzheimer disease (AD), having an earlier diagnosis allows patients to comprehend the underlying causes of the disease, and empowers them to make well-informed choices on managing their lifestyle.¹ Moreover, providers relying on evidence-based diagnostic criteria enables them to accurately ascertain the presence or absence of AD in their patients, facilitating appropriate diagnosis and treatment.

Recently, a draft proposal for new AD diagnostic criteria was presented to at the 2023 Alzheimer’s Association International Conference, July 16-20, in Amsterdam, the Netherlands.¹ The inclusion of blood-based biomarkers, which demonstrates remarkable potential and accuracy in detecting AD, became a noteworthy addition to the revised criteria. The blood biomarkers have a user-friendly nature and are affordable, making them accessible to diverse populations, particularly those in underserved and rural communities.

Following the news, Maria Carrillo, PhD, chief science officer for the Alzheimer's Association, shared her insights on the revised guidelines with NeurologyLive®. She talked about how the updated diagnostic guidelines have changed since their initial publication in 2011. She also spoke about the role that blood-based biomarkers play in the revised NIA-AA guidelines, and why they are considered a significant advancement. Additionally, Carillo explained how the evidence-based diagnostic criteria can help clinicians and patients in the detection as well as the management of AD.

NeurologyLive: In a brief summary, what is the history of the diagnostic criteria guidelines for Alzheimer disease?

The National Institute on Aging and the Alzheimer’s Association (NIA-AA) convened workgroups who published diagnostic guidelines in 2011 across the disease continuum (preclinical because of AD, mild cognitive impairment because of AD, dementia because of AD) and a research framework for moving forward the hypothesis of AD as a biological disease in 2018. [Read the 2018 research framework and the 2011 clinical guidelines.]

These efforts have supported recommendations for the diagnosis and characterization of AD. Several core principles emerged from these efforts, including:

• AD should be defined biologically, not based on a clinical syndrome(s).
• The disease is a continuum that begins with the appearance of brain pathology in asymptomatic individuals and progresses through stages of increasing pathologic burden eventually leading to the appearance and progression of clinical symptoms.
• The disease is diagnosed in vivo by abnormalities on core biomarkers.

In early 2022, the Alzheimer’s Association convened a steering committee to lead the revision of the NIA-AA framework. This workgroup, chaired by Clifford R. Jack, MD, presented their recommendations for the NIA-AA revised guidelines for clinical diagnosis of AD at AAIC 2023 for scientific input and review.

What was the motivation for updating the guidelines and what is different in the prosed one compared with the older ones?

First, no disease targeted therapies had received regulatory approval in 2018, but since then, several have. In response, the present document has progressed from a framework for research to criteria for diagnosis and staging that are intended for clinical use as well as research.

Second, validated biomarkers in 2018 were based on either CSF assays or imaging. Since then, plasma-based biomarkers with excellent diagnostic performance have been developed and clinically validated. The present document has correspondingly incorporated plasma biomarkers into updated criteria for biomarker categorization, disease diagnosis and staging.

Third, research studies have demonstrated that imaging and fluid biomarkers in a category are not equivalent for many use cases. In the present document, we have updated biomarker classification criteria to accommodate nonequivalence between fluid and imaging biomarkers within a category.

New to the draft revision is the incorporation of blood-based biomarkers, which have shown tremendous promise and performance in the ability to detect AD. Their ease of use and low cost allow them to be accessible to a wide variety of people, including underserved and rural populations. Importantly, some of the biomarkers described in the proposal have not yet been extensively tested in broadly representative populations and further analysis in these groups is urgently needed. The need for more representative cohorts is a cornerstone position of the Alzheimer’s Association, and has been highlighted by the workgroup that developed these proposed diagnostic criteria.

In what ways do you think the AD community can benefit from using the new guidelines in their practice?

The next step is to gather and incorporate input from the AD community, including scientific and clinical audiences, with the goal of enabling earlier detection and greater diagnostic accuracy.

Once further revised and made available to the AD community, evidence-based diagnostic criteria can help doctors better determine if their patients do or do not have AD, so they can be diagnosed and treated appropriately.

For patients, early diagnosis helps people understand the cause of their cognitive challenges so they can make informed decisions about how they want to manage their lives.

Transcript edited for clarity. Click here for more coverage of AAIC 2023.

REFERENCES
1. Proposed New Diagnostic Criteria for Alzheimer’s Disease Unveiled at AAIC 2023. News Release. Alzheimer’s Association. Published July 16, 2023. Accessed July 26, 2023. https://aaic.alz.org/releases_2023/new-alzheimers-diagnostic-criteria-unveiled.asp