A new combined blood test for cognitive decline boasts a 90% accuracy rate in determining whether memory loss is due to Alzheimer’s disease, according to a recent study. This is a significant improvement over the diagnostic accuracy of neurologists and memory specialists, who correctly diagnosed Alzheimer’s in 73% of cases, and primary care doctors, who had a 61% accuracy rate.
The blood test, known as plasma phosphorylated tau 217 (p-tau217), is among several blood biomarkers being evaluated for diagnosing mild cognitive impairment and early-stage Alzheimer’s disease. The test measures tau protein 217, an excellent indicator of amyloid pathology, said Dr. Sebastian Palmqvist, an associate professor and senior consultant neurologist at Lund University in Sweden. “Increases in p-tau217 concentrations in the blood are quite profound in Alzheimer’s disease. At the dementia stage of the disease, levels are more than 8 times higher compared to the elderly without Alzheimer’s,” Palmqvist explained.
Research published in January found that a similar p-tau217 test is up to 96% accurate in identifying elevated levels of beta-amyloid and up to 97% accurate in identifying tau. The presence of beta-amyloid plaques and tau tangles in the brain are hallmark signs of Alzheimer’s disease.
In the new study, the p-tau217 test was combined with another blood biomarker for Alzheimer’s, the amyloid 42/40 ratio, which measures two types of amyloid proteins. This combination, called the amyloid probability score, was the most predictive of Alzheimer’s disease.
“We’d love to have a blood test that can be used in a primary care physician’s office, functioning like a cholesterol test but for Alzheimer’s,” said Dr. Maria Carrillo, chief science officer of the Alzheimer’s Association. “The p-tau217 blood test is turning out to be the most specific for Alzheimer’s and the one with the most validity. It seems to be the front-runner,” said Carrillo, who oversees the association’s research initiatives, which partially funded the new study.
Highly accurate blood tests, once fully vetted, could revolutionize the speed of conducting Alzheimer’s trials and the development of new medications. “These are absolutely transformational times,” Carrillo added.
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