To investigate what might be observed when assaying samples with mixed AD/PiD pathology, we took AD and PiD brain homogenates with nominally comparable logSD50/mg tissue values, thus representing similar (within several fold) seeding doses of the tau aggregates therein, and mixed them together in ratios ranging from 10:0–0:10 AD:PiD before analyzing ThT fluorescence amplitudes in the K12 RT-QuIC. This evidence concerns the gene MTA2 and Alzheimer disease.