Background: In early onset dementia approximately one out of three patients has an atypical clinical presentation, which substantially complicates correct etiological diagnosis. [18 F]Flutemetamol PET, an investigational imaging agent, is being studied for detection of amyloid deposition, a pathological hallmark of Alzheimer's Disease (AD). In our ongoing study we examine the diagnostic value of [18 F]Flutemetamol PET in assessing patients with early onset dementia.
      Methods: We included 80 patients with early onset dementia (age <70 years) and physician diagnostic confidence less than 90% after a full routine diagnostic work-up for dementia. All patients underwent a [18 F]Flutemetamol PET scan which were visually assessed as amyloid positive or negative. Scans were performed between 90 and 110 minutes after injection of approximately 185 MBq [18 F]Flutemetamol. Before and after disclosing PET results to the patient's managing physician, clinical diagnosis and confidence in this diagnosis was determined. Also, the impact on patient healthcare management was assessed.
      Results: [18 F]Flutemetamol scans were positive in 48 out of 63 (76%) patients diagnosed (pre-PET imaging) with AD and 4 out of 17 (24%) patients diagnosed with other dementias. Overall, confidence in etiological diagnosis increased from 76±12% to 90±16% after disclosing PET results (p<0.001). Access to PET results led to a change in diagnosis in 16 (20%) patients. In 11 out of 13 patients, a negative PET scan caused a change of the initial AD diagnosis to another dementia. In 3 out of 4 other dementia patients, the initial diagnosis was changed to AD after receiving a positive PET scan. In 27 (34%) patients, PET results led to a change in patient healthcare management (i.e., 25 patients had their medication changed and 9 patients received additional care). These patients predominantly had a clinical diagnosis of AD. For 13 patients additional ancillary investigations were planned after access to the PET scan results.
      Conclusions: [18 F]Flutemetamol PET resulted in changes in the diagnostic process work-up of early onset dementia patients and the diagnostic confidence of the managing physicians. Especially in patients diagnosed with AD prior to PET, a negative PET scan resulted in more changes in clinical diagnosis and patient management.