JACKSONVILLE, Fla. — Alzheimer's disease, marked by memory loss, trouble concentrating and thinking, and changes in personality and behavior, devastates patients, their families and loved ones. With new treatments available for people with early signs of Alzheimer's disease, there is a growing need for accessible and cost-effective tests to diagnose Alzheimer's disease sooner. In a new study, Mayo Clinic researchers confirmed the accuracy of an FDA-approved blood test that can be used at outpatient memory clinics to diagnose the disease in patients with a range of cognitive impairment. The findings are published in Alzheimer's and Dementia: The Journal of the Alzheimer's Association.

Standard ways of measuring the buildup of toxic proteins in the brain that indicate Alzheimer's disease include positron emission tomography, or PET scans, and spinal taps. But these tests can be expensive and invasive. More accessible, non-invasive and cost-effective biomarkers — measurable indicators of a disease — are needed to improve diagnoses broadly in clinical settings. 

The research team says their findings show promise in:

• Better identifying research participants with Alzheimer's disease brain changes.
• Screening and selecting patients with Alzheimer's disease for clinical trials.
• Assessing how patients respond to therapy in clinical trials.
  

More than 500 patients receiving treatment for a range of memory issues at the outpatient Memory Disorder Clinic at Mayo Clinic in Florida participated in the study. They included patients with early- and late-onset cognitive impairment, typical and atypical Alzheimer's disease, Lewy body dementia and vascular cognitive impairment. 

Patients ranged from 32 to 89 years old, with the average age of symptom onset being 66. Alzheimer's disease was determined to be the underlying cause of the symptoms in 56% of the patients. The team also conducted serum tests to measure kidney disease, which can influence plasma biomarker concentrations. 

Mayo Clinic Laboratories tested for two proteins in blood plasma that are associated with amyloid plaque buildup, the hallmark of Alzheimer's disease: Aβ42/40 and p-tau217. The researchers found that p-tau217 levels were higher in patients with Alzheimer's disease versus those without the disease. Higher plasma p-tau217 concentrations were also associated with impaired kidney function, which researchers say should be taken into account when performing the blood test. 

Plasma p-tau217 concentrations were positive in 267 out of 509 patients, including 233 of 246 patients (95%) with cognitive impairment attributed to Alzheimer's disease.

The study was featured at the American Academy of Neurology Annual Meeting in April. 

In a previous study, researchers from the Mayo Clinic Laboratories team showed the utility of these blood tests compared to amyloid PET scans in research participants. 

Dr. Day says the next steps in this research are to evaluate blood-based testing in more diverse patient populations and people with early Alzheimer's disease who show no cognitive symptoms. The team also wants to evaluate disease-specific factors that may alter biomarker accuracy in clinical trials.

Other Mayo Clinic authors include Yoav Piura, M.D., Christian Lachner, M.D., Joshua Bornhorst, Ph.D., Alicia Algeciras Schimnich, Ph.D., and Neill Graff-Radford, M.D. For a full list of authors, funding and disclosures, see the paper.

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About Mayo Clinic
Mayo Clinic is a nonprofit organization committed to innovation in clinical practice, education and research, and providing compassion, expertise and answers to everyone who needs healing. Visit the Mayo Clinic News Network for additional Mayo Clinic news. 

Media contact:

• Tia Ford, Mayo Clinic Communications, newsbureau@mayo.edu

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