IC‐P‐204: PROGNOSTIC UTILITY OF MRI ATROPHY MEASURES IN AMCI PATIENTS WITH MINIMAL COGNITIVE DECLINE

The utility of MRI atrophy measures for predicting progression of amnestic MCI (aMCI) to Alzheimer's disease (AD) is limited, as evidenced by proven prognostic likelihood ratios (LR; positive LR = 2,9; negative LR = 0,49-0,56)(Frisoni et al., Neurology 2013) that are outside the ranges usually required for clinical implementation (LR+ ≥ 5,0 and LR- ≤ 0,2). We tested the hypothesis that stratification of patients by global cognitive function could improve the prognostic value of MRI. 4502We selected 147 aMCI subjects from the ADNI-1 database with MMSE = [28-30] at baseline and 195 with MMSE = [24-27] for which we had complete MRI volumetric results (FreeSurfer) and general primary-level information. We created a prognostic model for progression to AD within 36 months based on these measures. The model that included left hippocampal volume and left mid-temporal cortical thickness, when adjusted for intracranial volume, age and sex, had a 87,4% area under ROC curve (AUC), 80.3% classification accuracy, 53,8% sensitivity, 88,2% specificity, LR+ = 4,81 and LR- = 0.49 (with classification cut-point of disease probability = 0.4). After excluding statistical outliers (three subjects; impact chi-square (dl 6)=12.59), the same model had AUC of 91,1%, 81.9% classification accuracy, 71.4% sensitivity, 85.3% specificity, LR+=4.9 and LR-=0.3 (with classification cut-point of 0.3). Applying the same model to the ADNI aMCI subjects with baseline MMSE in the [24-27]range gave a AUC of 64.5 %. In fact, simply adding a dichotomous variable in the MRI model for cognitive status (i.e. baseline MMSE in range [24-27] or [28-30]) gives a AUC of 73.3% for all aMCI in the ADNI-1 population. A clinically relevant prognostic significance for left hippocampal volume and left mid-temporal cortical thickness, when adjusted for intracranial volume, age and sex, has been observed in ADNI-1 aMCI subjects with baseline MMSE in the [28-30] range. The prognostic LR+ and LR- observed in these strata is higher than previously described for a more general population and reaches clinical applicability.

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