Diagnostic value of amyloid-PET and tau-PET: a head-to-head comparison

Abstract

Purpose Assess the individual and combined diagnostic value of amyloid-PET and tau-PET in a memory clinic population. Methods Clinical reports of 136 patients were randomly assigned to two diagnostic pathways: AMY-TAU, amyloid-PET is presented before tau-PET; and TAU-AMY, tau-PET is presented before amyloid-PET. Two neurologists independently assessed all reports with a balanced randomized design, and expressed etiological diagnosis and diagnostic confidence (50–100%) three times: (i) at baseline based on the routine diagnostic workup, (ii) after the first exam (amyloid-PET for the AMY-TAU pathway, and tau-PET for the TAU-AMY pathway), and (iii) after the remaining exam. The main outcomes were changes in diagnosis (from AD to non-AD or vice versa) and in diagnostic confidence. Results Amyloid-PET and tau-PET, when presented as the first exam, resulted in a change of etiological diagnosis in 28% (p = 0.006) and 28% (p < 0.001) of cases, and diagnostic confidence increased by 18% (p < 0.001) and 19% (p < 0.001) respectively, with no differences between exams (p > 0.05). We observed a stronger impact of a negative amyloid-PET versus a negative tau-PET (p = 0.014). When added as the second exam, amyloid-PET and tau-PET resulted in a further change in etiological diagnosis in 6% (p = 0.077) and 9% (p = 0.149) of cases, and diagnostic confidence increased by 4% (p < 0.001) and 5% (p < 0.001) respectively, with no differences between exams (p > 0.05). Conclusion Amyloid-PET and tau-PET significantly impacted diagnosis and diagnostic confidence in a similar way, although a negative amyloid-PET has a stronger impact on diagnosis than a negative tau-PET. Adding either of the two as second exam further improved diagnostic confidence. Trial number PB 2016-01346.

The Clinical Use of Alzheimer’s Biomarkers in Patients With Mild Cognitive Impairment: A European Alzheimer’s Disease Consortium Survey

“…However, when the focus switched from the theoretical belief to the perceived clinical utility of PET scans assessing amyloid and tau, responders did not show a clear preference for amyloid-PET. Consistently, a recent work assessing the diagnostic value of amyloid-PET and tau-PET in a memory clinic population, showed that the two exams signi cantly impacted diagnosis and diagnostic con dence in a similar way [4]. Notably, clinicians and biomarker experts proved to be perfectly aligned both with regard to beliefs on the pathogenic role of amyloid and tau and to the perceived clinical utility of amyloid-PET and tau-PET.…”

“…Their use will probably increase as new effective therapies will become available. It must be remarked that the frequency of use of each biomarker is clearly in uenced by its local availability, which varies signi cantly from center to center with MRI being already widely available and tau-PET being available only in research contexts, despite the promising preliminary results exhibited since its recent introduction [4,17]. Of note, the limited frequency of use detected for amyloid-PET and tau-PET might be in uenced by the lack of reimbursement for this examination.…”

“…Even if this mainly represents a research framework, it points to the clinical relevance of AD biomarkers, and supports their increasing use in clinical practice. Consistently, several studies demonstrated that the use of biomarkers has different clinical implications [3][4][5][6] with MCI patients being the ones who might bene t the most from biomarker testing [7]. Indeed, an early etiological diagnosis of AD in MCI patients should initiate speci c counseling [8] and allow interventions to potentially delay the progression to dementia [9].…”

Is Amyloid Burden Measured by 18F-Flutemetamol PET Associated with Progression in Clinical Alzheimer’s Disease?

“…Previous studies state that the main value of A␤-PET on a group level is the high negative predictive value [5][6][7]. However, research groups have recently assessed the usefulness of A␤-PET imaging, demonstrating its value in terms of change in diagnosis [8,9] and management [10].…”

Molecular imaging and fluid biomarkers of Alzheimer’s disease neuropathology: an opportunity for integrated diagnostics

“…Comparative studies should namely measure the incremental diagnostic value provided by a test, i.e., not only its diagnostic performance but also its added value when other information, for example the result of gateway or other tests, is already available. There are only a few diagnostic studies measuring this parameter [10][11][12], one in this issue comparing the incremental diagnostic value of amyloid PET and tau PET [13]. The limited evidence on the comparison and combination of biomarkers presumably contributes to explain the variable policies for coverage across countries and the lack of widely accepted detailed diagnostic algorithms [1,2].…”