18F PET with florbetaben for the early diagnosis of Alzheimer’s disease dementia and other dementias in people with mild cognitive impairment
Review question: In people with mild cognitive impairment (MCI), does using a 18F PET scan with florbetaben predict progression to Alzheimer’s disease dementia (ADD) and other dementias?
Due to global ageing, the number of people with dementia is expected to increase dramatically in the next few decades. Diagnosing dementia at an early stage is desirable, but there is no widespread agreement on the best approach. A range of simple pen and paper tests used by healthcare professionals can assess people with poor memory or cognitive impairment. Whether or not using special PET scans that detect amyloid —one of the hallmarks of Alzheimer’s disease— improves our ability to predict the progression from MCI to ADD or other forms of dementia remains unclear. Since these tests are expensive, it is important that they provide additional benefits.
We aimed to evaluate the accuracy of the 18F-florbetaben PET scan in identifying those people with MCI who clinically progress to ADD, other types of dementia, or any form of dementia over a period of time.
The evidence is current to May 2017. We found 1 study including 45 participants with MCI with a follow-up of 4 years; gender was not reported and the median age for those with a PET-positive scan by quantitative assessment was 73.5 years old. For those with a PET-negative scan the mean age was 71.8 years old. Participants were mainly recruited from local memory clinics.
Study funding sources: the study was funded by the test manufacturer.
Quality of the evidence
The main limitation of this review was that our findings were based on only one study, with not enough details on how the participants were selected. The study was considered to be at high risk of bias, since the final ADD diagnosis was not established separately from the scan results, and due to potential conflicts of interest detected.
In this review, based on only one study, we found that the 18F-florbetaben PET scan, as a single test with visual assessment, correctly classified 100% of the participants who will progress to ADD and 83% of the participants who did not progress to ADD at four years follow-up. This means that in a cohort with 100 participants with MCI, 47 of whom will progress to ADD, we would expect that all those 47 MCI participants would test positive with the 18F-florbetaben scan and that 0 participants would be falsely negative (i.e. none of the 47 participants would have a negative test and yet progress to ADD). In addition, we would expect 44 of 53 participants who did not progress to ADD to be 18F-florbetaben-negative and 9 to be falsely positive (i.e. 9 of the 53 participants would have a positive test but not progress to ADD).
The small size of the included study lowered our confidence on these estimates of accuracy and it is still possible that the test is considerably less accurate than these results suggest.
We conclude that 18F-florbetaben imaging is a promising test to predict the progression from MCI to ADD; however, we need more studies to clearly demonstrate its accuracy.