Introduction: In the absence of a gold standard for in vivo Alzheimer disease (AD) diagnosis,
AD biomarkers such as cerebrospinal fluid biomarkers (CSF-B) and PET-Amyloid are considered
diagnostically useful in clinical practice guidelines and have consensual appropriate use criteria (AUC).
However, little evidence has been published on their utilization in the clinical setting or on approaches
to mismatched results. The objective of this work was to evaluate the use of AD biomarkers in clinical
practice, focusing on the implementation of PET-Amyloid in cases of inconclusive CSF-B.
Methods: This naturalistic, ambispective case series included patients fulfilling AUC for CSF-B and
PET-Amyloid whose CSF-B results were non-diagnostic (target population), analyzing the diagnostic
certainty, the treatment approach, and the relationship between CSF-B and PET-Amyloid results.
Results: Out of 2373 eligible patients, AD biomarkers were studied in 417 (17.6%), most frequently due
to cognitive impairment in under 65-year-olds, using CSF-B in 311 patients and PET-Amyloid in 150.
CSF-B results were non-diagnostic for 44 patients (52.3% male; aged 60.9±6.6 years), who then underwent
PET-Amyloid study, which was positive in 31. A ‘k’ coefficient of 0.108 was obtained between
CSF-B and PET-amyloid (54.5% concordance). In multivariate regression analysis, Aβ42 was the only
significant predictor (p= 0.018) of a positive PET-Amyloid result. In the target population, PETAmyloid
increased diagnostic confidence by 53.7% (p <0.001) and modified the therapeutic approach in
36.4% of cases.
Conclusion: These findings support the duplication of AD biomarkers and demonstrate that the implementation
of PET-Amyloid provides an early and certain diagnosis to guide appropriate treatment.