MAPT and Alzheimer disease: In this system, evidence of abnormal tau and/or neurodegeneration biomarkers, in the absence of Aβ pathology, are defined as "non-AD pathologic change". Importantly, the IWG have also proposed guidelines for the identification of these states with the use of biomarkers [69], but are less definitive than the NIA-AA workgroup on the primacy of Aβ measurements.