Platelet Amyloid Precursor Protein Abnormalities in Mild Cognitive Impairment Predict Conversion to Dementia of Alzheimer Type A 2-Year Follow-up Study

Background: Alteration of the amyloid precursor protein (APP) forms ratio has been described in the platelets of patients with dementia of Alzheimer type (DAT) and in a subset of subjects with mild cognitive impairment (MCI). Objective: To evaluate the potential role of the platelet APP forms ratio in predicting progression from MCI to DAT. Design: Thirty subjects with MCI underwent a clinical and neuropsychological examination and a determination of the platelet APP forms ratio. Subjects were followed up periodically for 2 years, and the progression to dementia was evaluated. Setting: Community population-based sample of patients admitted for memory complaints. Results: Patients who progressed to DAT at the 2-year follow-up (n = 12) showed a significant decrease of baseline platelet APP forms ratio values (mean ± SD, 0.36 ± 0.28) compared with stable MCI subjects (mean ± SD, 0.73 ± 0.32) (P<01) and patients who developed other types of dementia (mean ± SD, 0.83 ± 0.27) (P=.03). By fixing a cutoff score of 0.6, 10 (83%) of the 12 DAT patients showed baseline values below the cut-off, whereas 10 (71%) of 14 subjects who either developed non-Alzheimer-type dementia or maintained cognitive functions had values in the normal range. Conclusion: Mild cognitive impairment is a major risk factor for DAT, and Alzheimer disease-related pathological changes can be identified in patients converting to DAT within a 2-year follow-up.