An operational approach to National Institute on Aging-Alzheimer's Association criteria for preclinical Alzheimer disease
ABSTRACT A workgroup commissioned by the Alzheimer's Association (AA) and the National Institute on Aging (NIA) recently published research criteria for preclinical Alzheimer disease (AD). We performed a preliminary assessment of these guidelines.
We employed Pittsburgh compound B positron emission tomography (PET) imaging as our biomarker of cerebral amyloidosis, and (18) fluorodeoxyglucose PET imaging and hippocampal volume as biomarkers of neurodegeneration. A group of 42 clinically diagnosed AD subjects was used to create imaging biomarker cutpoints. A group of 450 cognitively normal (CN) subjects from a population-based sample was used to develop cognitive cutpoints and to assess population frequencies of the different preclinical AD stages using different cutpoint criteria.
The new criteria subdivide the preclinical phase of AD into stages 1 to 3. To classify our CN subjects, 2 additional categories were needed. Stage 0 denotes subjects with normal AD biomarkers and no evidence of subtle cognitive impairment. Suspected non-AD pathophysiology (SNAP) denotes subjects with normal amyloid PET imaging, but abnormal neurodegeneration biomarker studies. At fixed cutpoints corresponding to 90% sensitivity for diagnosing AD and the 10th percentile of CN cognitive scores, 43% of our sample was classified as stage 0, 16% stage 1, 12 % stage 2, 3% stage 3, and 23% SNAP.
This cross-sectional evaluation of the NIA-AA criteria for preclinical AD indicates that the 1-3 staging criteria coupled with stage 0 and SNAP categories classify 97% of CN subjects from a population-based sample, leaving only 3% unclassified. Future longitudinal validation of the criteria will be important.
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- "Finally, we summed up the volume of both hippocampi as we were not primarily interested in lateralization-specific effects and normalized each subject's hippocampal volume with estimated total intracranial volume (eTIV). The normalized hippocampal volume (HVn) was calculated as the residual from a linear regression between hippocampal volume (y) and total intracranial volume (x) (Jack et al., 2012), resulting in the regression formula y (mm³) = 5101 + 1.51 * 10 -3 * eTIV + ε. "
ABSTRACT: Objective: Paired associative stimulation (PAS) is a widely used transcranial magnetic stimulation (TMS) paradigm to induce synaptic long-term potentiation (LTP)-like plasticity in the intact human brain. The PAS effect is reduced in Alzheimer's dementia (AD) but has not yet been assessed in patients with mild cognitive impairment (MCI). Methods: PAS was assessed in a group of 24 MCI patients and 24 elderly controls. MCI patients were further stratified by their cognitive profile as well as hippocampal atrophy and Apolipoprotein E (ApoE) genotype. Results: There was no difference in PAS effects between MCI patients and healthy controls. MCI patients tended to show a higher response rate and an average PAS effect. PAS effects were not correlated with markers of disease severity or ApoE genotype but were more pronounced in individuals with shorter sleep duration and in MCI subjects with higher ratings of subjective alertness. Conclusions: Contrary to our initial hypothesis, there was no clear difference in PAS between MCI patients and healthy controls. Significance: Our results argue against a continuous reduction of LTP-like plasticity along the spectrum of clinical MCI when stratified by MCI-subtype, APOE genotype or hippocampus atrophy.Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 08/2015; DOI:10.1016/j.clinph.2015.08.010 · 3.10 Impact Factor
Journal of Alzheimer's disease: JAD 07/2015; 47(1):253-270. DOI:10.3233/JAD-141494 · 4.15 Impact Factor
- "We hypothesized that asymmetry in olfactory function could be an early predictor of AD and, hence, that it could distinguish between MCI and age-matched healthy controls. Crucially, we selected a uniform population of MCI patients with positive amyloid PET, a biomarker currently considered as the hallmark of AD patients at a predemential stage of the disease  and compared them with a group of healthy, amyloid-negative age-matched controls . Furthermore, we also compared the MCI group to a group of patients presenting with a primary olfactory dysfunction (post-viral olfactory loss). "
Journal of Alzheimer's disease: JAD 07/2015; 47(1):231-242. DOI:10.3233/JAD-150128 · 4.15 Impact Factor
- "A strength of the present study was the use of individual test scores and actuarial neuropsychological criteria to operationalize subtle cognitive decline within the same conceptual framework we have previously used to define MCI . This method of defining subtle cognitive decline may improve diagnostic consistency and reliability compared to the use of " self-complaint of memory decline or subtle neurobehavioral changes, "  which has been shown to cloud rather than clarify diagnosis , or the use of composite scores    in which sensitive and insensitive test performances are averaged together, with the result that the composite score's sensitivity to subtle cognitive decline is likely reduced. A direction for future research will be to examine individual neuropsychological markers of subtle cognitive decline against different methods of constructing composite scores (e.g., principle components analysis, item response theory)  to determine which method most reliably predicts progression. "