Abstract: A method of detecting a disease associated with abnormal protein aggregation in a subject is provided, the method comprising (a) contacting leukocytes from the subject with a probe that binds to pathogenic protein aggregates, and (b) detecting the probe bound to the pathogenic protein aggregates, wherein the presence of pathogenic protein aggregates in the leukocytes is indicative that the subject has a disease associated with abnormal protein aggregation. In one embodiment, the disease is Alzheimer's disease or mild cognitive impairment.