Clinical neuropathology practice news 3-2012: the "ABC" in AD-revised and updated guideline for the neuropathologic assessment of Alzheimer's disease.

The two major approaches for the neuropathological assessment of Alzheimer's disease (AD) related pathology have been based on the assessment of neuritic plaques (CERAD) and neurofibrillary pathology (Braak and Braak). In 1997 these two approaches were integrated in the criteria and recommendations of the National Institute on Aging and the Reagan Institute Working group. Recently a new guideline has been published by the National Institute on Aging-Alzheimer's Association. This new guideline recognizes the existence of a pre-clinical stage of AD as part of continuous neuropathological changes in the background of the disease process, and it fosters the assessment of amyloid-beta phases in addition to neurofibrillary degeneration and neuritic plaques following an "ABC" score. Further, it suggests protocols for the neuropathological assessment of additional/concomitant neurodegenerative and vascular pathologies. Altogether, the new guideline responds to the need for an update of the existing "1997 criteria" for AD. Continued studies will have to assess the added value of the new approach and the influence of interlaboratory and/or methodological differences on the implementation of these new recommendations.