Request for Amyloid PET in Arm 3
AD
The proportion of enrolled arm 3 participants who underwent amyloid PET during the study was 243 of 278 participants (87%). This proportion is not different from that of arm 1 and arm 2 participants who underwent amyloid PET during the study, 268 of 291 (92%) and 234 of 271 (86%), respectively (We observed that the main reasons for performing an amyloid PET were related to diagnostic uncertainty (unclear diagnosis in 147/243 cases [60%] and need to prove or exclude AD in 105/243 cases [43%] and 78/243 cases [32%], respectively), followed by participant preference (patient wanted an amyloid PET scan in 26/243 cases [11%] and refused lumbar puncture in 13/243 cases [5%]) (eTable 5 in 