HIPPOCAMPAL MEAN DIFFUSIVITY FOR THE DIAGNOSIS OF DEMENTIA AND MILD COGNITIVE IMPAIRMENT IN A PRIMARY CARE SAMPLE

Abstract

Mean diffusivity (MD) in the hippocampus, as measured by diffusion tensor imaging (DTI), has been shown to be a useful diagnostic marker for differentiating patients with Mild Cognitive Impairment (MCI) and Alzheimer's dementia (AD) from cognitively healthy control subjects (HC). However, the marker has not been evaluated for patients from primary care, who vary systematically from patients recruited from specialized care settings. In a previous study, hippocampus volume reached a lower diagnostic accuracy in MCI patients recruited from a primary care setting, as compared to a specialized care setting (Teipel et al., 2017, JAD). The present study compared diagnostic accuracy of hippocampal MD for MCI and dementia between patients recruited from a specialized care setting and patients recruited from primary care. We hypothesized diagnostic accuracy to be lower in the primary care sample. We recruited a primary care sample (n= 70) from a primary care intervention trial (DelpHi-MV) and a specialized setting sample (n= 70) from our memory clinic. The samples included dementia patients (AD and mixed dementia), MCI patients and HC, and were matched pairwise for diagnosis, age, gender, and education. We calculated MD for the left and right hippocampus. Within each sample, we used left or right hippocampal MD, respectively, as predictor for diagnosis in a logistic regression, controlling for age. The predicted probabilities were entered in a receiver operating curve and resulting areas under the curves were evaluated using cross-validation. In the primary care sample, hippocampal MD significantly detected dementia with high accuracy (left: AUC= 0.92; right: AUC= 0.85), but did not classify MCI with an accuracy above chance (left: AUC= 0.60; right: AUC= 0.47). In the specialized setting sample, hippocampal MD was a significant classifier with high accuracy for both dementia (left: AUC= 0.91; right: AUC= 0.91) and MCI (left: AUC= 0.86; right: AUC= 0.83). Our results suggest that hippocampal MD measures may aid the identification of dementia in primary care as well as in specialized care settings. However, in contrast to specialized care settings, hippocampal MD measures may not contribute to the detection of MCI in primary care.