As blood biomarkers become increasingly common and accessible in research and clinical settings due to their non-invasive nature and cost-effectiveness, it is crucial to understand their full range of use cases. A deeper understanding of their scope will help determine if their interpretation should be considered alongside cognitive assessments. A recent study by a French research team led by Vincent Bouteloup, used data from two large French cohorts, MEMENTO and BALTAZAR, to investigate whether the predictive value of Alzheimer’s disease blood biomarkers (e.g. p-tau217 protein) varies depending on a person’s cognitive profile. The aim was to determine if cognitive phenotyping enhances diagnostic accuracy. The study included 969 participants recruited from two French memory clinics. Participants without dementia were classified into three groups: 1) those with Subjective Cognitive Impairment, 2) those with Mild Cognitive Impairment with a common Alzheimer’s disease phenotype and 3) those with Mild Cognitive Impairment with uncommon Alzheimer’s disease phenotypes or other phenotypes. Significant differences were observed in the accuracy of p-tau217 blood tests in predicting Alzheimer’s disease-related brain changes (i.e. brain amyloidosis), as well as in its positive predictive value. This was true for both published and internally developed diagnostic cut-off points. The study’s results suggest that cognitive phenotyping is crucial for interpreting blood p-tau217 concentrations in member clinics, as it determines the pre-test probability of being amyloid positive.
