A prospective study evaluating the clinical utility of tau‐PET in the diagnostic work‐up of patients with cognitive symptoms

Abstract

AbstractBackgroundDetermining the added value of tau‐PET in the diagnostic work‐up of patients with cognitive symptoms is of great importance before implementation of the method in clinical practice. We therefore aimed to prospectively study the added clinical value of including tau‐PET in the clinical work‐up.Method878 patients referred for cognitive complaints to secondary Memory clinics in southern Sweden were consecutively recruited to the Swedish BioFINDER‐2 cohort study (May 2017 – Sept 2021). Participants underwent a baseline diagnostic work‐up including clinical examination, medical history, cognitive testing, blood and CSF sampling, and MRI of the brain. A tau‐PET ([18F]RO948) scan was added onto this clinical diagnostic work‐up. The tau‐PET scans were visually read as: normal, early AD pattern, late AD pattern or inconclusive scan. The primary end points were change in diagnosis and change in Alzheimer disease drug therapy or other drug treatment between the pre‐ and post‐PET visits. Secondary end point was the change in diagnostic certainty between the pre‐ and post‐PET visits.ResultThe tau‐PET visual read result led to a change in diagnoses in 66 participants (7.5%, p<0.001) and a change in medication in 48 participants (5.5%, p<0.001) (Figure 1). There was an overall increase in the diagnostic certainty after tau‐PET in the whole dataset [6.9±2.3 vs 7.4±2.4; p<0.0001]. The certainty was higher in participants with a pre‐PET diagnosis of AD [7.6±1.7 vs 8.2±2.0; p<0.0001] (Figure 2) and increased, as expected, even further in participants with a tau‐PET positive result supporting an AD diagnosis [8.0±1.4 vs 9.0±0.9; p<0.0001]. The impact of tau‐PET results was strongest in participants with pathological Ab‐status, whereas no significant change in diagnoses was seen in participants with normal Ab‐status.ConclusionWe report a significant change in diagnoses and medication of patients when tau‐PET is added to an already extensive diagnostic work‐up that included CSF AD biomarkers. Tau‐PET led to a significant increase in certainty of underlying etiology. The additive effect on certainty of etiology and to diagnosis was predominantly seen in Ab‐positives and we suggest that clinical use of tau‐PET is limited to populations with biomarkers indicating Ab‐positivity.