Multisite assessment of NIA-AA guidelines for the neuropathologic evaluation of Alzheimer's disease.

Neuropathologic assessment is the current "gold standard" for evaluating the Alzheimer's disease (AD), but there is no consensus on the methods used. Fifteen unstained slides (8 brain regions) from each of the 14 cases were prepared and distributed to 10 different National Institute on Aging AD Centers for application of usual staining and evaluation following recently revised guidelines for AD neuropathologic change. Current practice used in the AD Centers Program achieved robustly excellent agreement for the severity score for AD neuropathologic change (average weighted κ = .88, 95% confidence interval: 0.77-0.95) and good-to-excellent agreement for the three supporting scores. Some improvement was observed with consensus evaluation but not with central staining of slides. Evaluation of glass slides and digitally prepared whole-slide images was comparable. AD neuropathologic evaluation as performed across AD Centers yields data that have high agreement with potential modifications for modest improvements.