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—The letter of Drs Neumann and Cohn raises the issue of the lack of histologic confirmation in our study. We are sympathetic with their desire for neuropathologic data and we fully discussed our own concern at the outset of the "Comment" section, where we stated:It is possible that, in the absence of confirmatory histopathologic studies, patients with other disorders may have been included in our population because their symptoms resembled those of PDDAT [primary degenerative dementia of the Alzheimer type]. There is no reason, however, to believe that the likelihood of including any such incorrectly diagnosed patients would have varied systematically as a function of the age group assignments. That is to say, any diagnostic errors of this sort could not account for the differences observed between the two groups, which were defined on the basis of the AAO [age at onset] of dementia.This is a fundamental point;
Sherwin I, Seltzer B. Neuropathologic Data in Alzheimer's Disease-Reply. Arch Neurol. 1983;40(13):830–831. doi:10.1001/archneur.1983.04050120080021