JAMA
Alzheimer’s blood test shows high accuracy in both primary and secondary care settings
The amyloid probability score 2 (APS2), a blood test that combines tau protein and amyloid plaque measurements, resulted in high diagnostic accuracy, positive predictive value (PPV), and negative predictive value (NPV) for plasma samples collected from patients at primary and secondary care clinics.
- In this study, 1,213 patients (mean age, 74.2 years; 48% women) who were undergoing clinical evaluation of cognitive symptoms in primary (n=515) or secondary care (n=698) underwent testing to determine whether the APS2 could accurately identify AD.
- The test performed comparably well in both primary and secondary care settings. When samples were analyzed in a single batch in the primary care cohort, AUC was 0.97 when the APS2 was used, PPV was 91%, and NPV was 92%. In the secondary care cohort, the AUC was 0.96 when the APS2 was used, the PPV was 88%, and the NPV was 87%.
- The APS2 also performed consistently in prospectively collected plasma samples analyzed biweekly. When the samples were analyzed prospectively (biweekly) in the primary care cohort, AUC was 0.96 when the APS2 was used, PPV was 88%, and NPV was 90%. In the secondary care cohort, AUC was 0.97 when the APS2 was used, PPV was 91%, and NPV was 91%.
- Primary care physicians had a diagnostic accuracy of 61% for identifying clinical AD after clinical examination, cognitive testing, and CT scan vs. 91% using the APS2. Dementia specialists had a diagnostic accuracy of 73% vs. 91% using the APS2. In the overall population, the diagnostic accuracy using the APS2 (90%) wasn't different from the diagnostic accuracy using the percentage of p-tau217 alone (90%).
Source:
Palmqvist S, et al. (2024, July 28). JAMA. Blood Biomarkers to Detect Alzheimer Disease in Primary Care and Secondary Care. https://pubmed.ncbi.nlm.nih.gov/39068545/