NEW YORK – Researchers from Lund University in Sweden and their collaborators have developed a new blood test that appears to be more accurate than standard clinical evaluation in diagnosing Alzheimer's disease.
“This blood test had high diagnostic accuracy for identifying Alzheimer's disease among individuals with cognitive symptoms in primary and secondary care, providing superior performance compared with the diagnostic accuracy after standard clinical evaluation,” senior and corresponding author Oskar Hansson, a professor at Lund University, and colleagues wrote in a study published in the Journal of the American Medical Association on Sunday, concurrent with the Alzheimer's Association International Conference in Philadelphia, where the data were also presented.
The researchers developed their test, dubbed the amyloid probability score 2, or APS2 for short, based on two blood biomarkers: the ratio of plasma phosphorylated tau 217 (p-tau217) relative to non-p-tau217, and the ratio of amyloid-β 42 to amyloid-β 40 in plasma.
For their study, the team applied the test, which uses mass spectrometry, to 1,213 patients undergoing clinical evaluation due to cognitive symptoms in Sweden. The average age of the participants was around 74 years old, and about half of them were women. Blood samples were shipped from clinics biweekly and analyzed in batches.
Overall, the researchers showed that APS2 had higher accuracy for detecting Alzheimer's disease in primary and secondary care settings compared with doctors’ diagnoses of these patients, which were based on clinical examination, cognitive tests, and CT scans.
Specifically, of the 515 patients evaluated in a primary care setting, physicians made accurate diagnoses for only 63 percent of Alzheimer's cases, while APS2 had a diagnostic accuracy of around 90 percent. Meanwhile, among 698 patients seen at memory clinics, APS2 was around 90 percent accurate at identifying Alzheimer's disease while specialists only identified 73 percent correctly.
Additionally, the researchers noted the APS2 test's accuracy despite the fact that 26 percent of patients in the primary care cohort had comorbidities, such as kidney disease.
"Notably, these were the results of blood samples that have been shipped biweekly for analysis from primary care units, which is similar to routine clinical practice," Sebastian Palmqvist, a clinical memory researcher at Lund University and the paper’s first author, said in a statement. "These results were especially impressive considering that older populations in primary care often have medical conditions that can influence or vary the concentrations of p-tau217."
Although the results were promising, the study also had several limitations. For one, the researchers noted that future validation in cohorts from other countries is necessary, especially those that may have a lower prevalence of amyloid positivity.
The investigators also pointed out the need to evaluate fully automated immunoassays that may be more practical for implementing the test at local clinical chemistry laboratories, as mass spectrometry is still challenging to carry out and has high equipment costs.
Still, with further validation, the researchers believe their Alzheimer's blood test could be deployed to help screen patients with symptoms for Alzheimer's in the clinic.
"We see this as a major step towards global clinical implementation of an Alzheimer's blood test," Hansson said in a statement. "It highlights the need for Alzheimer's biomarkers in making a correct diagnosis more of the time.”