%0 Journal Article %J J Alzheimers Dis %D 2023 %T Characterizing Performance Gaps of a Code-Based Dementia Algorithm in a Population-Based Cohort of Cognitive Aging. %A Vassilaki, Maria %A Fu, Sunyang %A Christenson, Luke R %A Garg, Muskan %A Petersen, Ronald C %A St Sauver, Jennifer %A Sohn, Sunghwan %K Alzheimer Disease %K Cognitive Aging %K Cognitive Dysfunction %K Dementia %K Disease Progression %K Female %K Humans %K Male %X

BACKGROUND: Multiple algorithms with variable performance have been developed to identify dementia using combinations of billing codes and medication data that are widely available from electronic health records (EHR). If the characteristics of misclassified patients are clearly identified, modifying existing algorithms to improve performance may be possible.

OBJECTIVE: To examine the performance of a code-based algorithm to identify dementia cases in the population-based Mayo Clinic Study of Aging (MCSA) where dementia diagnosis (i.e., reference standard) is actively assessed through routine follow-up and describe the characteristics of persons incorrectly categorized.

METHODS: There were 5,316 participants (age at baseline (mean (SD)): 73.3 (9.68) years; 50.7% male) without dementia at baseline and available EHR data. ICD-9/10 codes and prescription medications for dementia were extracted between baseline and one year after an MCSA dementia diagnosis or last follow-up. Fisher's exact or Kruskal-Wallis tests were used to compare characteristics between groups.

RESULTS: Algorithm sensitivity and specificity were 0.70 (95% CI: 0.67, 0.74) and 0.95 (95% CI: 0.95, 0.96). False positives (i.e., participants falsely diagnosed with dementia by the algorithm) were older, with higher Charlson comorbidity index, more likely to have mild cognitive impairment (MCI), and longer follow-up (versus true negatives). False negatives (versus true positives) were older, more likely to have MCI, or have more functional limitations.

CONCLUSIONS: We observed a moderate-high performance of the code-based diagnosis method against the population-based MCSA reference standard dementia diagnosis. Older participants and those with MCI at baseline were more likely to be misclassified.

%B J Alzheimers Dis %V 95 %P 931-940 %8 2023 %G eng %N 3 %R 10.3233/JAD-230344 %0 Journal Article %J J Alzheimers Dis %D 2016 %T Characterizing White Matter Tract Degeneration in Syndromic Variants of Alzheimer's Disease: A Diffusion Tensor Imaging Study. %A Madhavan, Ajay %A Schwarz, Christopher G %A Duffy, Joseph R %A Strand, Edythe A %A Machulda, Mary M %A Drubach, Daniel A %A Kantarci, Kejal %A Przybelski, Scott A %A Reid, Robert I %A Senjem, Matthew L %A Gunter, Jeffrey L %A Apostolova, Liana G %A Lowe, Val J %A Petersen, Ronald C %A Jack, Clifford R %A Josephs, Keith A %A Whitwell, Jennifer L %K Aged %K Alzheimer Disease %K Aniline Compounds %K Anisotropy %K Aphasia, Primary Progressive %K Case-Control Studies %K Diffusion Tensor Imaging %K Female %K Humans %K Image Processing, Computer-Assisted %K Male %K Middle Aged %K Nerve Fibers, Myelinated %K Neurodegenerative Diseases %K Neuropsychological Tests %K Positron-Emission Tomography %K Psychiatric Status Rating Scales %K Retrospective Studies %K Thiazoles %K White Matter %X

BACKGROUND: Different clinical syndromes can arise from Alzheimer's disease (AD) neuropathology, including dementia of the Alzheimer's type (DAT), logopenic primary progressive aphasia (lvPPA), and posterior cortical atrophy (PCA).

OBJECTIVE: To assess similarities and differences in patterns of white matter tract degeneration across these syndromic variants of AD.

METHODS: Sixty-four subjects (22 DAT, 24 lvPPA, and 18 PCA) that had diffusion tensor imaging and showed amyloid-β deposition on PET were assessed in this case-control study. A whole-brain voxel-based analysis was performed to assess differences in fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity across groups.

RESULTS: All three groups showed overlapping diffusion abnormalities in a network of tracts, including fornix, corpus callosum, posterior thalamic radiations, superior longitudinal fasciculus, inferior longitudinal fasciculus, inferior fronto-occipital fasciculus, and uncinate fasciculus. Subtle regional differences were also observed across groups, with DAT particularly associated with degeneration of fornix and cingulum, lvPPA with left inferior fronto-occipital fasciculus and uncinate fasciculus, and PCA with posterior thalamic radiations, superior longitudinal fasciculus, posterior cingulate, and splenium of the corpus callosum.

CONCLUSION: These findings show that while each AD phenotype is associated with degeneration of a specific structural network of white matter tracts, striking spatial overlap exists among the three network patterns that may be related to AD pathology.

%B J Alzheimers Dis %V 49 %P 633-43 %8 2016 %G eng %N 3 %1 http://www.ncbi.nlm.nih.gov/pubmed/26484918?dopt=Abstract %R 10.3233/JAD-150502 %0 Journal Article %J Lancet Neurol %D 2013 %T Tracking pathophysiological processes in Alzheimer's disease: an updated hypothetical model of dynamic biomarkers. %A Jack, Clifford R %A Knopman, David S %A Jagust, William J %A Petersen, Ronald C %A Weiner, Michael W %A Aisen, Paul S %A Shaw, Leslie M %A Vemuri, Prashanthi %A Wiste, Heather J %A Weigand, Stephen D %A Lesnick, Timothy G %A Pankratz, Vernon S %A Donohue, Michael C %A Trojanowski, John Q %K Alzheimer Disease %K Amyloid beta-Peptides %K Biomarkers %K Cognition Disorders %K Humans %K Models, Biological %K Nonlinear Dynamics %K tau Proteins %X

In 2010, we put forward a hypothetical model of the major biomarkers of Alzheimer's disease (AD). The model was received with interest because we described the temporal evolution of AD biomarkers in relation to each other and to the onset and progression of clinical symptoms. Since then, evidence has accumulated that supports the major assumptions of this model. Evidence has also appeared that challenges some of our assumptions, which has allowed us to modify our original model. Refinements to our model include indexing of individuals by time rather than clinical symptom severity; incorporation of interindividual variability in cognitive impairment associated with progression of AD pathophysiology; modifications of the specific temporal ordering of some biomarkers; and recognition that the two major proteinopathies underlying AD biomarker changes, amyloid β (Aβ) and tau, might be initiated independently in sporadic AD, in which we hypothesise that an incident Aβ pathophysiology can accelerate antecedent limbic and brainstem tauopathy.

%B Lancet Neurol %V 12 %P 207-16 %8 2013 Feb %G eng %N 2 %1 http://www.ncbi.nlm.nih.gov/pubmed/23332364?dopt=Abstract %R 10.1016/S1474-4422(12)70291-0 %0 Journal Article %J Ann Neurol %D 2012 %T An operational approach to National Institute on Aging-Alzheimer's Association criteria for preclinical Alzheimer disease. %A Jack, Clifford R %A Knopman, David S %A Weigand, Stephen D %A Wiste, Heather J %A Vemuri, Prashanthi %A Lowe, Val %A Kantarci, Kejal %A Gunter, Jeffrey L %A Senjem, Matthew L %A Ivnik, Robert J %A Roberts, Rosebud O %A Rocca, Walter A %A Boeve, Bradley F %A Petersen, Ronald C %K Aged %K Aged, 80 and over %K Alzheimer Disease %K Aniline Compounds %K Biomarkers %K Brain %K Cognition Disorders %K Disease Progression %K Female %K Fluorodeoxyglucose F18 %K Humans %K Longitudinal Studies %K Male %K Mental Status Schedule %K National Institute on Aging (U.S.) %K Neuropsychological Tests %K Positron-Emission Tomography %K Thiazoles %K United States %X

OBJECTIVE: 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.

METHODS: 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.

RESULTS: 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.

INTERPRETATION: 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.

%B Ann Neurol %V 71 %P 765-75 %8 2012 Jun %G eng %N 6 %1 http://www.ncbi.nlm.nih.gov/pubmed/22488240?dopt=Abstract %R 10.1002/ana.22628 %0 Journal Article %J Alzheimers Dement %D 2011 %T The diagnosis of mild cognitive impairment due to Alzheimer's disease: recommendations from the National Institute on Aging-Alzheimer's Association workgroups on diagnostic guidelines for Alzheimer's disease. %A Albert, Marilyn S %A DeKosky, Steven T %A Dickson, Dennis %A Dubois, Bruno %A Feldman, Howard H %A Fox, Nick C %A Gamst, Anthony %A Holtzman, David M %A Jagust, William J %A Petersen, Ronald C %A Snyder, Peter J %A Carrillo, Maria C %A Thies, Bill %A Phelps, Creighton H %K Alzheimer Disease %K Biomarkers %K Cognition Disorders %K Diagnosis, Differential %K Diagnostic Imaging %K Humans %K National Institute on Aging (U.S.) %K Practice Guidelines as Topic %K Societies, Medical %K United States %X

The National Institute on Aging and the Alzheimer's Association charged a workgroup with the task of developing criteria for the symptomatic predementia phase of Alzheimer's disease (AD), referred to in this article as mild cognitive impairment due to AD. The workgroup developed the following two sets of criteria: (1) core clinical criteria that could be used by healthcare providers without access to advanced imaging techniques or cerebrospinal fluid analysis, and (2) research criteria that could be used in clinical research settings, including clinical trials. The second set of criteria incorporate the use of biomarkers based on imaging and cerebrospinal fluid measures. The final set of criteria for mild cognitive impairment due to AD has four levels of certainty, depending on the presence and nature of the biomarker findings. Considerable work is needed to validate the criteria that use biomarkers and to standardize biomarker analysis for use in community settings.

%B Alzheimers Dement %V 7 %P 270-9 %8 2011 May %G eng %N 3 %1 http://www.ncbi.nlm.nih.gov/pubmed/21514249?dopt=Abstract %R 10.1016/j.jalz.2011.03.008 %0 Journal Article %J Arch Neurol %D 2011 %T Evidence for ordering of Alzheimer disease biomarkers. %A Jack, Clifford R %A Vemuri, Prashanthi %A Wiste, Heather J %A Weigand, Stephen D %A Aisen, Paul S %A Trojanowski, John Q %A Shaw, Leslie M %A Bernstein, Matthew A %A Petersen, Ronald C %A Weiner, Michael W %A Knopman, David S %K Aged %K Aged, 80 and over %K Alzheimer Disease %K Amyloid beta-Peptides %K Biomarkers %K Female %K Hippocampus %K Humans %K Longitudinal Studies %K Male %K Mild Cognitive Impairment %K tau Proteins %X

OBJECTIVE: To empirically assess the concept that Alzheimer disease (AD) biomarkers significantly depart from normality in a temporally ordered manner.

DESIGN: Validation sample.

SETTING: Multisite, referral centers.

PARTICIPANTS: A total of 401 elderly participants in the Alzheimer's Disease Neuroimaging Initiative who were cognitively normal, who had mild cognitive impairment, or who had AD dementia. We compared the proportions of 3 AD biomarker values (the Aβ42 level in cerebrospinal fluid [CSF], the total tau level in CSF, and the hippocampal volume adjusted for intracranial volume [hereafter referred to as the adjusted hippocampal volume]) that were abnormal as cognitive impairment worsened. Cut points demarcating normal vs abnormal for each biomarker were established by maximizing diagnostic accuracy in independent autopsy samples.

MAIN OUTCOME MEASURES: Three AD biomarkers (ie, the CSF Aβ42 level, the CSF total tau level, and the adjusted hippocampal volume).

RESULTS: Within each clinical group of the entire sample (n = 401), the CSF Aβ42 level was abnormal more often than was the CSF total tau level or the adjusted hippocampal volume. Among the 298 participants with both baseline and 12-month data, the proportion of participants with an abnormal Aβ42 level did not change from baseline to 12 months in any group. The proportion of participants with an abnormal total tau level increased from baseline to 12 months in cognitively normal participants (P = .05) but not in participants with mild cognitive impairment or AD dementia. For 209 participants with an abnormal CSF Aβ42 level at baseline, the percentage with an abnormal adjusted hippocampal volume but normal CSF total tau level increased from baseline to 12 months in participants with mild cognitive impairment. No change in the percentage of MCI participants with an abnormal total tau level was seen between baseline and 12 months.

CONCLUSIONS: A reduction in the CSF Aβ42 level denotes a pathophysiological process that significantly departs from normality (ie, becomes dynamic) early, whereas the CSF total tau level and the adjusted hippocampal volume are biomarkers of downstream pathophysiological processes. The CSF total tau level becomes dynamic before the adjusted hippocampal volume, but the hippocampal volume is more dynamic in the clinically symptomatic mild cognitive impairment and AD dementia phases of the disease than is the CSF total tau level.

%B Arch Neurol %V 68 %P 1526-35 %8 2011 Dec %G eng %N 12 %1 http://www.ncbi.nlm.nih.gov/pubmed/21825215?dopt=Abstract %R 10.1001/archneurol.2011.183