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Early amyloid PET scan improves aetiological diagnosis among memory clinic patients

An early amyloid PET scan provides a high certainty diagnosis in memory clinic patients three months after their diagnosis, according to a new study.

Amyloid-β is the predominant pathologic protein in Alzheimer’s disease (AD) and which affects disease progression and prognosis. Moreover, an amyloid-imaging PET tracer, provides quantitative information on the extent of these protein deposits in living subjects. Despite this, other work suggests the current appropriate use criteria for imaging cannot effectively identify patients who will benefit from such imaging.

In the current study, researchers sought to assess the value of amyloid scanning in patients from a memory clinic. They wondered if a PET scan performed soon after the patient’s diagnosis, enabled a more confident aetiological diagnosis. Patients had either subjective cognitive decline with symptoms of preclinical AD, mild cognitive impairment or dementia.

Researchers randomly placed individuals into three arms. Arm one (early scan), arm two (scan after eight months) and arm three (scan at the physician’s discretion). The aetiological diagnoses were grouped into three main categories: AD; non-AD and undetermined. The primary outcome was the proportion of participants receiving a high confidence (>90%) etiological diagnosis in arms one and two after three months.

High confidence diagnosis

The study included 840 patients with a similar proportion in each of the three arms. The prevalence of amyloid positivity was higher in those with a baseline diagnosis of AD versus participants with non-AD (69% vs 36%, p < 0.001) at baseline.

After three months, 40% of arm one patients and 11% in arm two, had high confidence diagnosis (p < 0.001). This effect was consistent across cognitive stages.

The findings led to authors to conclude that an early amyloid PET allowed memory clinic patients to receive an aetiological diagnosis with very high confidence after only three months. The findings supported the implementation of amyloid PET early in the diagnostic workup of memory clinic patients.