[The early diagnosis and differential diagnosis of Alzheimer's disease with clinical methods].

Alzheimer's disease is a progressive and fatal neurodegenerative disorder in which the novel drugs can slow down the progression in the early phase. Our purpose was to find biological markers, which would detect neuropathology in the prodromal and early phase of Alzheimer's disease. Beside the routine diagnostic methods, neuropsychological test, auditory event related potential and special laboratory tests were performed among subjects with Alzheimer's disease, vascular dementia, mild cognitive impairment and major depression compared to a healthy control group. Visual Paired Associate Learning was impaired in all patient groups, in major depression it seemed to be reversible. In amnestic mild cognitive impairment and in dementia a longer latency of late component of auditory evoked potential, P300, was found. Reduced paraoxonase activity in the serum and increased Nepsilon(gamma-glutamyl)lysine isodipeptide concentration in the cerebrospinal fluid were detected in both dementia groups. Characteristic changes of Visual Paired Associate Learning and P300 might predict the conversion to Alzheimer's disease in mild cognitive impairment. The paraoxonase activity and the isodipeptide concentration can be sensitive markers of the pathomechanism of neurodegeneration. A combined use of the above-mentioned methods can help in the early prediction and diagnosis of Alzheimer's disease.