Quantitation of PET signal as an adjunct to visual interpretation of florbetapir imaging.

PURPOSE: This study examined the feasibility of using quantitation to augment interpretation of florbetapir PET amyloid imaging. METHODS: A total of 80 physician readers were trained on quantitation of florbetapir PET images and the principles for using quantitation to augment a visual read. On day 1, the readers completed a visual read of 96 scans (46 autopsy-verified and 50 from patients seeking a diagnosis). On day 2, 69 of the readers reinterpreted the 96 scans augmenting their interpretation with quantitation (VisQ method) using one of three commercial software packages. A subset of 11 readers reinterpreted all scans on day 2 based on a visual read only (VisVis control). For the autopsy-verified scans, the neuropathologist's modified CERAD plaque score was used as the truth standard for interpretation accuracy. Because an autopsy truth standard was not available for scans from patients seeking a diagnosis, the majority VisQ interpretation of the three readers with the best accuracy in interpreting autopsy-verified scans was used as the reference standard. RESULTS: Day 1 visual read accuracy was high for both the autopsy-verified scans (90%) and the scans from patients seeking a diagnosis (87.3%). Accuracy improved from the visual read to the VisQ read (from 90.1% to 93.1%, p < 0.0001). Importantly, access to quantitative information did not decrease interpretation accuracy of the above-average readers (>90% on day 1). Accuracy in interpreting the autopsy-verified scans also increased from the first to the second visual read (VisVis group). However, agreement with the reference standard (best readers) for scans from patients seeking a diagnosis did not improve with a second visual read, and in this cohort the VisQ group was significantly improved relative to the VisVis group (change 5.4% vs. -1.1%, p < 0.0001). CONCLUSION: These results indicate that augmentation of visual interpretation of florbetapir PET amyloid images with quantitative information obtained using commercially available software packages did not reduce the accuracy of readers who were already performing with above average accuracy on the visual read and may improve the accuracy and confidence of some readers in clinically relevant cases.

Effectiveness of Florbetapir PET Imaging in Changing Patient Management.

AIMS: To evaluate the impact of amyloid PET imaging on diagnosis and patient management in a multicenter, randomized, controlled study. METHODS: Physicians identified patients seeking a diagnosis for mild cognitive impairment or dementia, possibly due to Alzheimer disease (AD), and recorded a working diagnosis and a management plan. The patients underwent florbetapir PET scanning and were randomized to either immediate or delayed (1-year) feedback regarding amyloid status. At the 3-month visit, the physician updated the diagnosis and recorded a summary of the actual patient management since the post-scan visit. The study examined the impact of immediate versus delayed feedback on patient diagnosis/management at 3 and 12 months. RESULTS: A total of 618 subjects were randomized (1:1) to immediate or delayed feedback arms, and 602 subjects completed the 3-month primary endpoint visit. A higher proportion of patients in the immediate feedback arm showed a change in diagnosis compared to the controls (32.6 vs. 6.4%; p = 0.0001). Similarly, a higher proportion of patients receiving immediate feedback had a change in management plan (68 vs. 55.5%; p < 0.002), mainly driven by changes in AD medication. Specifically, acetylcholinesterase inhibitors were prescribed to 67% of the amyloid-positive and 27% of the amyloid-negative subjects in the information group compared with 56 and 43%, respectively, in the control group (p < 0.0001). These between-group differences persisted until the 12-month visit. CONCLUSION: Knowledge of the amyloid status affects the diagnosis and alters patient management.