Sarah E. Monsell

Accuracy of the Clinical Diagnosis of Alzheimer Disease at National Institute on Aging Alzheimer Disease Centers, 2005–2010

Abstract The neuropathologic examination is considered to provide the gold standard for Alzheimer disease (AD). To determine the accuracy of currently used clinical diagnostic methods, clinical and neuropathologic data from the National Alzheimer’s Coordinating Center, which gathers information from the network of National Institute on Aging (NIA)-sponsored Alzheimer Disease Centers (ADCs), were collected as part of the National Alzheimer’s Coordinating Center Uniform Data Set (UDS) between 2005 and 2010. A database search initially included all 1198 subjects with at least one UDS clinical assessment and who had died and been autopsied; 279 were excluded as being not demented or because critical data fields were missing. The final subject number was 919. Sensitivity and specificity were determined based on “probable” and “possible” AD levels of clinical confidence and 4 levels of neuropathologic confidence based on varying neuritic plaque densities and Braak neurofibrillary stages. Sensitivity ranged from 70.9% to 87.3%; specificity ranged from 44.3% to 70.8%. Sensitivity was generally increased with more permissive clinical criteria and specificity was increased with more restrictive criteria, whereas the opposite was true for neuropathologic criteria. When a clinical diagnosis was not confirmed by minimum levels of AD histopathology, the most frequent primary neuropathologic diagnoses were tangle-only dementia or argyrophilic grain disease, frontotemporal lobar degeneration, cerebrovascular disease, Lewy body disease and hippocampal sclerosis. When dementia was not clinically diagnosed as AD, 39% of these cases met or exceeded minimum threshold levels of AD histopathology. Neurologists of the NIA-ADCs had higher predictive accuracy when they diagnosed AD in subjects with dementia than when they diagnosed dementing diseases other than AD. The misdiagnosis rate should be considered when estimating subject numbers for AD studies, including clinical trials and epidemiologic studies.

Reversion from mild cognitive impairment to normal or near-normal cognition Risk factors and prognosis

Objectives: We sought to identify characteristics of individuals with mild cognitive impairment (MCI) that are associated with a relatively high probability of reverting back to normal cognition, and to estimate the risk of future cognitive decline among those who revert. Methods: We first studied 3,020 individuals diagnosed with MCI on at least 1 visit to an Alzheimers Disease Center in the United States. All underwent standardized Uniform Data Set evaluations at their first visit with an MCI diagnosis and on a subsequent visit, about 1 year later, at which cognitive status was reassessed. Multiple logistic regression was used to identify predictors of reverting from MCI back to normal cognition. We then estimated the risk of developing MCI or dementia over the next 3 years among those who had reverted, compared with individuals who had not had a study visit with MCI. Results: About 16% of subjects diagnosed with MCI reverted back to normal or near-normal cognition approximately 1 year later. Five characteristics assessed at the first MCI visit contributed significantly to a model predicting a return to normal cognition: Mini-Mental State Examination (MMSE) score, Clinical Dementia Rating (CDR) score, MCI type, Functional Activities Questionnaire (FAQ) score, and APOE ϵ4 status. Survival analysis showed that the risk of retransitioning to MCI or dementia over the next 3 years was sharply elevated among those who had MCI and then improved, compared with individuals with no history of MCI. Conclusions: Even in a cohort of patients seen at dementia research centers, reversion from MCI was fairly common. Nonetheless, those who reverted remained at increased risk for future cognitive decline.

Body mass index, weight change, and clinical progression in mild cognitive impairment and Alzheimer disease.

The speed and severity of clinical progression after Alzheimer disease (AD) diagnosis varies and depends on multiple factors, most not well elucidated. We assessed whether body mass index (BMI) and 1-year weight change (WC) are associated with clinical progression in amnestic mild cognitive impairment (aMCI) and early-stage AD. Longitudinal data comprising 2268 aMCI and 1506 AD participants in the National Alzheimer’s Coordinating Center’s Uniform Data Set were used to examine nuances of clinical progression by BMI and WC, as well as potential variations in associations by age, sex, BMI (WC model), or apolipoprotein E genotype. In aMCI, high BMI (vs. moderate BMI) was associated with slower progression; weight loss (vs. no WC) was associated with faster progression. In AD, no significant differences were observed in clinical progression by BMI or WC. The association between BMI and clinical progression varied significantly by apolipoprotein E genotype in AD, and the association between WC and clinical progression varied significantly by sex and BMI in aMCI. Baseline BMI and 1-year WC in late life may serve as early prognostic indicators in aMCI and early-stage AD. If replicated, these results may help in counseling patients on anticipated clinical progression and suggest windows of opportunity for intervention.

Examination of the Clinicopathologic Continuum of Alzheimer Disease in the Autopsy Cohort of the National Alzheimer Coordinating Center

To test the hypothesis that Alzheimer disease (AD) is a clinical and pathologic continuum between normal aging and end-stage dementia, we selected a convenience sample of subjects from the National Alzheimer Coordinating Center 2005 to 2012 autopsy cohort (n = 2,083) with the last clinical evaluation within 2 years before autopsy and no other primary neuropathologic diagnosis. Demographic and neuropathologic characteristics were correlated with the Clinical Dementia Rating-Sum of Boxes in the 835 subjects meeting these criteria. Both neuritic plaques and neurofibrillary tangles independently predicted Clinical Dementia Rating-Sum of Boxes. Severe small-vessel disease, severe amyloid angiopathy, and hippocampal sclerosis were also independently associated with the degree of cognitive impairment. By contrast, education was a strong independent protective factor against cognitive deficits. The cause of mild to moderate dementia remained uncertain in 14% of the patients. Inverse probability weighting suggests the generalizability of these results to nonautopsied cohorts. These data indicate that plaques and tangles independently contribute to cognitive impairment, that concurrent vascular disease strongly correlates with cognitive dysfunction even in a sample selected to represent the AD pathologic continuum, and that education further modifies clinical expression. Thus, multiple concomitant etiologies of brain damage and premorbid characteristics contribute to the uncertainty of AD clinicopathologic correlations based only on tangles and plaques.

Mild to Moderate Alzheimer Dementia with Insufficient Neuropathological Changes

Recently, ∼16% of participants in an anti‐Aβ passive immunotherapy trial for mild‐to‐moderate Alzheimer disease (AD) had a negative baseline amyloid positron emission tomography (PET) scan. Whether they have AD or are AD clinical phenocopies remains unknown. We examined the 2005–2013 National Alzheimers Coordinating Center autopsy database and found that ∼14% of autopsied subjects clinically diagnosed with mild‐to‐moderate probable AD have no or sparse neuritic plaques, which would expectedly yield a negative amyloid PET scan. More than half of these “Aβ‐negative” subjects have low neurofibrillary tangle Braak stages. These findings support the implementation of a positive amyloid biomarker as an inclusion criterion in future anti‐Aβ drug trials. Ann Neurol 2014;75:597–601

Neuropsychological changes in asymptomatic persons with Alzheimer disease neuropathology

Objective: To determine whether asymptomatic persons with Alzheimer disease (AD) neuropathologic change differ in the trajectory of their cognitive performance compared to asymptomatic persons without AD neuropathologic change. Methods: Longitudinal performance on standard neuropsychological tests was examined in participants who died within 2 years of their last cognitive assessment and who were never diagnosed with mild cognitive impairment or dementia (Clinical Dementia Rating global score of 0 at all assessments). Using cognitive and neuropathologic data collected between 2005 and 2013 from the 34 National Institute on Aging–sponsored Alzheimers Disease Centers, cognitive trajectories were compared for persons with and without evidence of AD neuropathologic change. We evaluated rates of decline in 4 domains (episodic memory, language, attention/working memory, executive function). The significance of the differences (β) in rates of decline was tested using linear regression, adjusting for age, education, sex, and other neuropathologic lesions. Results: Participants who had low to high levels of AD neuropathologic change (n = 131) showed a greater rate of decline on the attention/working memory domain score (β = −0.11; 95% confidence interval = −0.19, −0.02; p = 0.02) when compared to 80 participants who died without evidence of AD neuropathologic change. Conclusions: Clinically normal individuals who come to autopsy with AD neuropathologic change exhibit subtle evidence of declining cognitive trajectories for attention/working memory.

APOEε2 is associated with milder clinical and pathological Alzheimer disease

The Alzheimer disease (AD) APOEε4 risk allele associates with an earlier age at onset and increased amyloid‐β deposition, whereas the protective APOEε2 allele delays the onset and appears to prevent amyloid‐β deposition. Yet the clinical and pathological effects of APOEε2 remain uncertain because of its relative rarity. We investigated the effects of APOEε2 and ε4 alleles on AD pathology and cognition in a large US data set of well‐characterized AD patients.

Characterizing Apolipoprotein E ε4 Carriers and Noncarriers With the Clinical Diagnosis of Mild to Moderate Alzheimer Dementia and Minimal β-Amyloid Peptide Plaques

IMPORTANCE β-Amyloid peptide (Aβ) plaques are a cardinal neuropathologic feature of Alzheimer disease (AD), yet more than one-third of apolipoprotein E ε4 (APOE4) noncarriers with the clinical diagnosis of mild to moderate Alzheimer dementia may not meet positron emission tomographic criteria for significant cerebral amyloidosis. OBJECTIVES To clarify the percentage of APOE4 carriers and noncarriers with the primary clinical diagnosis of mild to moderate Alzheimer dementia near the end of life and minimal Aβ plaques noted at autopsy and the extent to which these cases are associated with appreciable neurofibrillary degeneration or a primary neuropathologic diagnosis other than AD. DESIGN, SETTING, AND PARTICIPANTS Data on participants included in this study were obtained from the National Alzheimer Coordinating Centers Uniform Data Set, which comprises longitudinal clinical assessments performed at the AD centers funded by the National Institute on Aging. Neuropathology data are available for the subset of participants who died. A total of 100 APOE4 noncarriers and 100 APOE4 carriers had the primary clinical diagnosis of mild to moderate Alzheimer dementia at their last visit, known APOE4 genotype, died within the ensuing 24 months, and underwent neuropathologic evaluation on autopsy. The study was conducted from September 1, 2005, to September 1, 2012; analysis was performed from October 9, 2012, to March 20, 2015. MAIN OUTCOMES AND MEASURES Standardized histopathologic assessments of AD neuropathologic changes were the primary measures of interest in this study, specifically Consortium to Establish a Registry for Alzheimers Disease neuritic plaque density score, diffuse plaque density score, and Braak stage for neurofibrillary degeneration. The distributions of scores for these measures were the primary outcomes. RESULTS Of the 37 APOE4 noncarriers with minimal neuritic plaques, 16 individuals (43.2%) had Braak stages III to VI ratings, and 15 of the others (75.0%) met neuropathologic criteria for other dementia-related diseases. Of the 13 APOE4 carriers with minimal neuritic plaques, 6 individuals (46.2%) had Braak stages III to VI ratings and met neuropathologic criteria for other dementia-related diseases. Similarly, of the 7 APOE4 carriers with minimal neuritic plaques and Braak stages 0 to II, 4 participants (57.1%) were thought to have pathologic changes and alterations resulting from non-AD neuropathologic features. CONCLUSIONS AND RELEVANCE In this study, more than one-third of APOE4 noncarriers with the primary clinical diagnosis of mild to moderate Alzheimer dementia had minimal Aβ plaque accumulation in the cerebral cortex and, thus, may show limited or no benefit from otherwise effective anti-Aβ treatment. Almost half of the participants with a primary clinical diagnosis of mild to moderate Alzheimer dementia and minimal Aβ plaque accumulation had an extensive topographic distribution of neurofibrillary degeneration. Additional studies are needed to better understand and provide treatment for patients with this unexpectedly common cliniconeuropathologic condition.

Comparison of symptomatic and asymptomatic persons with Alzheimer disease neuropathology

Objectives: We sought to identify demographic and clinical features that were associated with expression of symptoms in the presence of Alzheimer disease (AD) neuropathologic changes. Methods: We studied 82 asymptomatic (Clinical Dementia Rating global score = 0) and 824 symptomatic subjects (Clinical Dementia Rating score >0) with low to high AD neuropathologic changes at autopsy who were assessed at 1 of 34 National Institute on Aging–funded Alzheimer’s Disease Centers. All subjects underwent a clinical examination within 1 year of death. Logistic regression was used to evaluate factors associated with the odds of being asymptomatic vs symptomatic. Results: Asymptomatic subjects tended to have low neurofibrillary tangle scores but a wide range of neuritic plaque frequencies. There were, however, a few asymptomatic subjects with very high tangle and neuritic plaque burden, as well as symptomatic subjects with few changes. In the multivariable model, asymptomatic subjects were older (odds ratio [OR] = 1.04; 95% confidence interval [CI] = 1.01–1.07), had lower clinical Hachinski Ischemic Score (OR = 0.82; 95% CI = 0.69–0.97), were less likely to have an APOE ε4 allele (OR = 0.36; 95% CI = 0.16–0.83), and had lower neurofibrillary tangle score (OR = 0.28; 95% CI = 0.17–0.45) compared with symptomatic subjects. Conclusions: Dissociating clinical symptoms from pathologic findings better allows for investigation of preclinical AD. Our results suggest that although the severity of the pathology, particularly neurofibrillary tangles, has a large role in determining the extent of symptoms, other factors, including age, APOE status, and comorbidities such as cerebrovascular disease also explain differences in clinical presentation.

Clinical Features of Alzheimer Disease With and Without Lewy Bodies

IMPORTANCE Lewy bodies are a frequent coexisting pathology in late-onset Alzheimer disease (AD). Previous studies have examined the contribution of Lewy bodies to the clinical phenotype of late-onset AD with variable findings. OBJECTIVE To determine whether the presence of Lewy body pathology influences the clinical phenotype and progression of symptoms in longitudinally assessed participants with AD. DESIGN, SETTING, AND PARTICIPANTS Retrospective clinical and pathological cohort study of 531 deceased participants who met the neuropathologic criteria for intermediate or high likelihood of AD according to the National Institute on Aging-Ronald Reagan Institute guidelines for the neuropathologic diagnosis of AD. All participants had a clinical assessment within 2 years of death. The data were obtained from 34 AD centers maintained by the National Alzheimer Coordinating Center and spanned from September 12, 2005, to April 30, 2013. EXPOSURES Standardized neuropathologic assessment and then brain autopsy after death. MAIN OUTCOMES AND MEASURES Clinical and neuropsychiatric test scores. RESULTS The mean (SD) age at death was statistically significantly younger for participants who had AD with Lewy bodies (77.9 [9.5] years) than for participants who had AD without Lewy bodies (80.2 [11.1] years) (P = .01). The mean (SD) age at onset of dementia symptoms was also younger for participants who had AD with Lewy bodies (70.0 [9.9] years) than for participants who had AD without Lewy bodies (72.2 [12.3] years) (P = .03). More men than women had AD with Lewy bodies (P = .01). The frequency of having at least 1 APOE ε4 allele was higher for participants who had AD with Lewy bodies than for participants who had AD without Lewy bodies (P = .03). After adjusting for age, sex, education, frequency of plaques (neuritic and diffuse), and tangle stage, we found that participants who had AD with Lewy bodies had a statistically significantly higher mean (SD) Neuropsychiatric Inventory Questionnaire score (6.59 [1.44] [95% CI, 3.75-9.42] vs 5.49 [1.39] [95% CI, 2.76-8.23]; P = .04) and a statistically significantly higher mean (SD) Unified Parkinson Disease Rating Scale motor score (0.81 [0.18] [95% CI, 0.45-1.17] vs 0.54 [0.18] [95% CI, 0.19-0.88]; P < .001) than did participants who had AD without Lewy bodies. CONCLUSIONS AND RELEVANCE Participants with both AD and Lewy body pathology have a clinical phenotype that may be distinguished from AD alone. The frequency of Lewy bodies in AD and the association of Lewy bodies with the APOE ε4 allele suggest potential common mechanisms for AD and Lewy body pathologies.