Test-retest variability of [18F]BAY 94-9172 studies in Alzheimer's disease and normal ageing

Objectives Aβ deposition can be examined in vivo using [18F]BAY 94-9172 and PET. In order to assess the response to anti-Aβ therapy it is important to know the test–retest variability of amyloid imaging PET scans. The aim of the present study was to assess test–retest variability of [18F]BAY 94-9172 PET studies in Alzheimer’s disease (AD) patients and age-matched healthy controls (HC).

Methods Test and retest static [18F]BAY 94-9172 scans (30 min duration) were acquired in 7 AD patients and 8 age-matched healthy controls, 2-4 weeks apart (median 3 weeks). Volumes of interest (VOI) were defined on the co-registered MRI scan and standardized uptake ratio values (SUVR) for all VOI were obtained using the cerebellar cortex as reference region.

Results AD patients displayed higher cortical [18F]BAY 94-9172 retention (2.0±0.3) than HC (1.3±0.2). In AD patients, cortical SUVR test–retest variability was 6.8% (range 0.6-12.2%, median 8.2%). In HC cortical SUVR test–retest variability was 2.9% (range 0.1-9.0%, median 2.8%). Combined test-retest variability was 4.7%. Variability was higher in smaller VOI.

Conclusions Overall, test-retest variability is similar to the one reported for PiB (Lopresti et al., 2005). Cortical test–retest variability in AD patients was higher than in HC.

Research Support The trial is sponsored and supported by Bayer-Schering Pharma AG