Abstract
Background: Biomarkers of neuronal injury and amyloid pathology play a
pivotal role in the diagnosis of Alzheimer’s disease (AD). The degree of AD biomarker
congruence is still unclear in clinical practice.
Objective: Diagnosis of AD with regard to the congruence of the clinical
diagnosis and different biomarkers.
Methods: In this prospective cross-sectional observational study, 54
patients with mild cognitive impairment or dementia due to AD or not due to AD were
investigated. Biomarkers of neuronal injury were medial temporal lobe atrophy (MTA) on
magnetic resonance imaging (MRI) and tau concentration in the cerebrospinal fluid (CSF).
CSF Aβ1-42 and amyloid-targeting positron emission tomography (PET) were
considered as biomarkers of amyloid pathology.
Results: Forty cases were diagnosed as AD and 14 cases were diagnosed as
non-AD based on clinical and routine MRI assessment. AD cases had higher MTA scores,
higher levels of CSF tau and lower levels of CSF Aβ1 - 42, and higher amyloid
load on PET compared to the non-AD group. In the AD group, completely consistently
pathological biomarkers were found in 32.5% , non-pathological in 5% . In 62.5% the
findings were inconsistent. Congruence of biomarkers was 67.5% for neuronal injury and for
amyloid dysfunction, respectively. In two patients, clinical diagnosis switched to non-AD
due to completely consistent non-pathological biomarker findings. The criteria of the
international working group were met in 75.0% .
Conclusion: Surprisingly, the number of completely congruent biomarkers was
relatively low. Interpretation of AD biomarkers is complicated by multiple biomarker
constellations. However, the level of biomarker consistency required to reliably diagnose
AD remains uncertain.
