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In this prospective longitudinal study, conducted in a large sample of amnestic MCI patients over a three-year period, we investigated the recently advanced proposal that unadjusted test scores obtained at baseline on long-term memory tests are more reliable than age- and education-corrected scores in predicting progression from aMCI to AD. Our experimental sample consisted of 270 aMCI patients who underwent extensive neurological and neuropsychological examinations both at baseline and at the follow-up, conducted at least 3 years later. At the follow-up 80 patients had converted to overt dementia. The predictive capacity of raw, age-corrected, education-corrected and fully corrected scores on RAVLT immediate and delayed recall was compared by examining the area under the ROC curves (AUCs) of all of these scores to assess which (raw or corrected) scores achieves the better reliability in predicting conversion to dementia. The condition (aMCI stable vs converted) was analyzed to assess the odds ratios resulting from a logistic regression on the corrected and uncorrected scores of RAVLT immediate and delayed recall. Even if both in immediate and in delayed recall the ROCs of 'raw scores' were generally higher than the other ROCs on corrected scores, these differences did not reach the level of statistical significance, failing to support the claim that unadjusted test scores are superior to age- and education-corrected scores in predicting progression from aMCI to AD.

Subjects with Mild Cognitive Impairment (MCI) are normally classified according to the presence of episodic memory deficits associated or not to disturbances of other cognitive domains. The present study had two aims: to identify discrete subtypes of amnestic MCI (a-MCI) with hippocampal atrophy; and to assess if the identified subtypes show different rates of progression to dementia. Sixty-seven a-MCI subjects were enrolled, all showing significant hippocampal atrophy on MRI. The subjects underwent at baseline and at follow-up a comprehensive neuropsychological examination, and were followed-up for five years to detect the conversion to dementia. An exploratory factor analysis on neuropsychological performances at baseline identified three main factors that were subsequently used to perform a k-means cluster analysis. Three cluster of a-MCI subjects were identified: "pure amnestic" (N=29), "multiple domain"(N=16), and "amnestic/semantic"(N=22). The successive discriminant functions were able to correctly classify 88% of the subjects. During the follow-up, 33 subjects converted to dementia (49.2%), 14 "pure amnestic" (48.3%), 11 "multiple domain" (68.5%) and 8 "amnestic/semantic" (36.4%; log-rank: p=0.016); median survival was respectively 36, 22, and 39 months. On Cox proportional hazard model, baseline MMSE (HR=0,709; p=0.006), education (HR=1,115; p=0.011) and belonging to the "multiple domain" subgroup (HR=2,706; p=0.013) were significantly associated to higher rate of conversion to dementia. Our findings confirm the tendency to worst outcome of subjects with multiple domain MCI, and show that the association of episodic and semantic memory deficits, without other cognitive disturbances, could identify a specific cognitive pattern associated to slower cognitive decline, as previously reported in Alzheimer's Disease.