Florey Department of Neuroscience and Mental Health - Research Publications
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ItemNo Preview AvailableCenTauR: Toward a universal scale and masks for standardizing tau imaging studies(WILEY, 2023-07)INTRODUCTION: Recently, an increasing number of tau tracers have become available. There is a need to standardize quantitative tau measures across tracers, supporting a universal scale. We developed several cortical tau masks and applied them to generate a tau imaging universal scale. METHOD: One thousand forty-five participants underwent tau scans with either 18F-flortaucipir, 18F-MK6240, 18F-PI2620, 18F-PM-PBB3, 18F-GTP1, or 18F-RO948. The universal mask was generated from cognitively unimpaired amyloid beta (Aβ)- subjects and Alzheimer's disease (AD) patients with Aβ+. Four additional regional cortical masks were defined within the constraints of the universal mask. A universal scale, the CenTauRz, was constructed. RESULTS: None of the regions known to display off-target signal were included in the masks. The CenTauRz allows robust discrimination between low and high levels of tau deposits. DISCUSSION: We constructed several tau-specific cortical masks for the AD continuum and a universal standard scale designed to capture the location and degree of abnormality that can be applied across tracers and across centers. The masks are freely available at https://www.gaain.org/centaur-project.
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ItemNationally Informed Recommendations on Approaching the Detection, Assessment, and Management of Mild Cognitive Impairment(IOS PRESS, 2022)Prior to the usual clinical symptoms of dementia, there can be subtle changes in cognitive function that differ from the normal age-related cognitive decline, which has been termed mild cognitive impairment (MCI). The increase in the numbers of individuals with possible MCI presenting to health care professionals, notably, General Practitioners (GPs), is going to rise dramatically in the coming years. With ever increasing demands on GPs, it is therefore timely to provide information that can be accessed by health care professionals to assist them in making appropriate diagnoses and to provide the most relevant, evidence-based treatment options. We have provided a comprehensive list of recommendations that aim to address key aspects of MCI in primary care. Specifically, these relate to detection and diagnosis; sharing the diagnosis, monitoring, and follow up; practical interventions to potentially delay progression; and personalizing care-planning, engagement, and patient motivation for the long term.
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Itemβ-amyloid PET harmonisation across longitudinal studies: Application to AIBL, ADNI and OASIS3(ACADEMIC PRESS INC ELSEVIER SCIENCE, 2022-11-15)INTRODUCTION: The Centiloid scale was developed to harmonise the quantification of β-amyloid (Aβ) PET images across tracers, scanners, and processing pipelines. However, several groups have reported differences across tracers and scanners even after centiloid conversion. In this study, we aim to evaluate the impact of different pre and post-processing harmonisation steps on the robustness of longitudinal Centiloid data across three large international cohort studies. METHODS: All Aβ PET data in AIBL (N = 3315), ADNI (N = 3442) and OASIS3 (N = 1398) were quantified using the MRI-based Centiloid standard SPM pipeline and the PET-only pipeline CapAIBL. SUVR were converted into Centiloids using each tracer's respective transform. Global Aβ burden from pre-defined target cortical regions in Centiloid units were quantified for both raw PET scans and PET scans smoothed to a uniform 8 mm full width half maximum (FWHM) effective smoothness. For Florbetapir, we assessed the performance of using both the standard Whole Cerebellum (WCb) and a composite white matter (WM)+WCb reference region. Additionally, our recently proposed quantification based on Non-negative Matrix Factorisation (NMF) was applied to all spatially and SUVR normalised images. Correlation with clinical severity measured by the Mini-Mental State Examination (MMSE) and effect size, as well as tracer agreement in 11C-PiB-18F-Florbetapir pairs and longitudinal consistency were evaluated. RESULTS: The smoothing to a uniform resolution partially reduced longitudinal variability, but did not improve inter-tracer agreement, effect size or correlation with MMSE. Using a Composite reference region for 18F-Florbetapir improved inter-tracer agreement, effect size, correlation with MMSE, and longitudinal consistency. The best results were however obtained when using the NMF method which outperformed all other quantification approaches in all metrics used. CONCLUSIONS: FWHM smoothing has limited impact on longitudinal consistency or outliers. A Composite reference region including subcortical WM should be used for computing both cross-sectional and longitudinal Florbetapir Centiloid. NMF improves Centiloid quantification on all metrics examined.
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ItemAmyloid and tau PET-positive cognitively unimpaired individuals are at high risk for future cognitive decline.(Springer Science and Business Media LLC, 2022-11)A major unanswered question in the dementia field is whether cognitively unimpaired individuals who harbor both Alzheimer's disease neuropathological hallmarks (that is, amyloid-β plaques and tau neurofibrillary tangles) can preserve their cognition over time or are destined to decline. In this large multicenter amyloid and tau positron emission tomography (PET) study (n = 1,325), we examined the risk for future progression to mild cognitive impairment and the rate of cognitive decline over time among cognitively unimpaired individuals who were amyloid PET-positive (A+) and tau PET-positive (T+) in the medial temporal lobe (A+TMTL+) and/or in the temporal neocortex (A+TNEO-T+) and compared them with A+T- and A-T- groups. Cox proportional-hazards models showed a substantially increased risk for progression to mild cognitive impairment in the A+TNEO-T+ (hazard ratio (HR) = 19.2, 95% confidence interval (CI) = 10.9-33.7), A+TMTL+ (HR = 14.6, 95% CI = 8.1-26.4) and A+T- (HR = 2.4, 95% CI = 1.4-4.3) groups versus the A-T- (reference) group. Both A+TMTL+ (HR = 6.0, 95% CI = 3.4-10.6) and A+TNEO-T+ (HR = 7.9, 95% CI = 4.7-13.5) groups also showed faster clinical progression to mild cognitive impairment than the A+T- group. Linear mixed-effect models indicated that the A+TNEO-T+ (β = -0.056 ± 0.005, T = -11.55, P < 0.001), A+TMTL+ (β = -0.024 ± 0.005, T = -4.72, P < 0.001) and A+T- (β = -0.008 ± 0.002, T = -3.46, P < 0.001) groups showed significantly faster longitudinal global cognitive decline compared to the A-T- (reference) group (all P < 0.001). Both A+TNEO-T+ (P < 0.001) and A+TMTL+ (P = 0.002) groups also progressed faster than the A+T- group. In summary, evidence of advanced Alzheimer's disease pathological changes provided by a combination of abnormal amyloid and tau PET examinations is strongly associated with short-term (that is, 3-5 years) cognitive decline in cognitively unimpaired individuals and is therefore of high clinical relevance.
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ItemPlasma p-tau181/A beta(1-42) ratio predicts A beta-PET status and correlates with CSF-p-tau181/A beta(1-42) and future cognitive decline(WILEY, 2022-01-01)BACKGROUND: In Alzheimer's disease (AD), plasma amyloid beta (Aβ)1-42 and phosphorylated tau (p-tau) predict high amyloid status from Aβ positron emission tomography (PET); however, the extent to which combination of these plasma assays can predict remains unknown. METHODS: Prototype Simoa assays were used to measure plasma samples from participants who were either cognitively normal (CN) or had mild cognitive impairment (MCI)/AD in the Australian Imaging, Biomarkers and Lifestyle (AIBL) study. RESULTS: The p-tau181/Aβ1-42 ratio showed the best prediction of Aβ-PET across all participants (area under the curve [AUC] = 0.905, 95% confidence interval [CI]: 0.86-0.95) and in CN (AUC = 0.873; 0.80-0.94), and symptomatic (AUC = 0.908; 0.82-1.00) adults. Plasma p-tau181/Aβ1-42 ratio correlated with cerebrospinal fluid (CSF) p-tau181 (Elecsys, Spearman's ρ = 0.74, P < 0.0001) and predicted abnormal CSF Aβ (AUC = 0.816; 0.74-0.89). The p-tau181/Aβ1-42 ratio also predicted future rates of cognitive decline assessed by AIBL Preclinical Alzheimer Cognitive Composite or Clinical Dementia Rating Sum of Boxes (P < 0.0001). DISCUSSION: Plasma p-tau181/Aβ1-42 ratio predicted both Aβ-PET status and cognitive decline, demonstrating potential as both a diagnostic aid and as a screening and prognostic assay for preclinical AD trials.
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ItemMethadone treatment and patient-directed hospital discharges among patients with opioid use disorder: Observations from general medicine services at an urban, safety-net hospital.(Elsevier BV, 2022-06)INTRODUCTION: People with opioid use disorder (OUD) have high rates of discharge against medical advice from the hospital. Interventions for addressing these patient-directed discharges (PDDs) are lacking. We sought to explore the impact of methadone treatment for OUD on PDD. METHODS: Using electronic record and billing data from an urban safety-net hospital, we retrospectively examined the first hospitalization on a general medicine service for adults with OUD from January 2016 through June 2018. Associations with PDD compared to planned discharge were examined using multivariable logistic regression. Administration patterns of maintenance therapy versus new in-hospital initiation of methadone were examined using bivariate tests. RESULTS: During the study time period, 1,195 patients with OUD were hospitalized. 60.6% of patients received medication for OUD, of which 92.8% was methadone. Patients who received no treatment for OUD had a 19.1% PDD rate while patients initiated on methadone in-hospital had a 20.5% PDD rate and patients on maintenance methadone during the hospitalization had a 8.6% PDD rate. In multivariable logistic regression, methadone maintenance was associated with lower odds of PDD compared to no treatment (aOR 0.53, 95% CI 0.34-0.81), while methadone initiation was not (aOR 0.89, 95% CI 0.56-1.39). About 60% of patients initiated on methadone received 30 mg or less per day. CONCLUSIONS: In this study sample, maintenance methadone was associated with nearly a 50% reduction in the odds of PDD. More research is needed to assess the impact of higher hospital methadone initiation dosing on PDD and if there is an optimal protective dose.
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ItemEvaluating buprenorphine prescribing and opioid-related health outcomes following the expansion the buprenorphine waiver program.(Elsevier BV, 2022-01)AIMS: To evaluate associations between new types of buprenorphine waivers (nurse practitioner and physician assistant [NP/PA]; 275-patient limit [MD/DO-275]) and both buprenorphine prescribing and health outcomes. METHODS: Using comprehensive county-level data from California 2010-2018, we modeled quarterly associations between numbers of NP/PA and MD/DO-275 waivers and rates of buprenorphine prescribing, opioid-related deaths, emergency department (ED) visits, and hospitalizations among all counties and separately among metropolitan and nonmetropolitan counties using Poisson regression models with county and quarter fixed effects and adjusting for time-varying covariates. RESULTS: Each additional NP/PA and MD/DO-275 waiver was associated with a 2.6% (95%CI: 1.1-4.1%) and 5.8% (4.1-7.4%) increase in buprenorphine prescribing among nonmetropolitan counties, respectively. Each additional MD/DO-275 waiver was associated with a 2.8% (1.0%-4.6%) increase in buprenorphine among metropolitan counties. There were no statistically significant associations between NP/PA waivers and buprenorphine prescribing among metropolitan counties or among either waiver type and opioid-related health outcomes. CONCLUSIONS: NP/PA waivers were associated with increased buprenorphine prescribing among nonmetropolitan counties and MD/DO-275 waivers were associated with increased buprenorphine prescribing among both metropolitan and nonmetropolitan counties.
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ItemNo Preview AvailableLeukocyte surface biomarkers implicate deficits of innate immunity in sporadic Alzheimer's disease(WILEY, 2022-11-09)INTRODUCTION: Blood-based diagnostics and prognostics in sporadic Alzheimer's disease (AD) are important for identifying at-risk individuals for therapeutic interventions. METHODS: In three stages, a total of 34 leukocyte antigens were examined by flow cytometry immunophenotyping. Data were analyzed by logistic regression and receiver operating characteristic (ROC) analyses. RESULTS: We identified leukocyte markers differentially expressed in the patients with AD. Pathway analysis revealed a complex network involving upregulation of complement inhibition and downregulation of cargo receptor activity and Aβ clearance. A proposed panel including four leukocyte markers - CD11c, CD59, CD91, and CD163 - predicts patients' PET Aβ status with an area under the curve (AUC) of 0.93 (0.88 to 0.97). CD163 was the top performer in preclinical models. These findings have been validated in two independent cohorts. CONCLUSION: Our finding of changes on peripheral leukocyte surface antigens in AD implicates the deficit in innate immunity. Leukocyte-based biomarkers prove to be both sensitive and practical for AD screening and diagnosis.
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ItemNo Preview AvailableAssociation of Elevated Amyloid and Tau Positron Emission Tomography Signal With Near-Term Development of Alzheimer Disease Symptoms in Older Adults Without Cognitive Impairment(AMER MEDICAL ASSOC, 2022-10)IMPORTANCE: National Institute on Aging-Alzheimer's Association (NIA-AA) workgroups have proposed biological research criteria intended to identify individuals with preclinical Alzheimer disease (AD). OBJECTIVE: To assess the clinical value of these biological criteria to identify older individuals without cognitive impairment who are at near-term risk of developing symptomatic AD. DESIGN, SETTING, AND PARTICIPANTS: This longitudinal cohort study used data from 4 independent population-based cohorts (PREVENT-AD, HABS, AIBL, and Knight ADRC) collected between 2003 and 2021. Participants were older adults without cognitive impairment with 1 year or more of clinical observation after amyloid β and tau positron emission tomography (PET). Median clinical follow-up after PET ranged from 1.94 to 3.66 years. EXPOSURES: Based on binary assessment of global amyloid burden (A) and a composite temporal region of tau PET uptake (T), participants were stratified into 4 groups (A+T+, A+T-, A-T+, A-T-). Presence (+) or absence (-) of neurodegeneration (N) was assessed using temporal cortical thickness. MAIN OUTCOMES AND MEASURES: Each cohort was analyzed separately. Primary outcome was clinical progression to mild cognitive impairment (MCI), identified by a Clinical Dementia Rating score of 0.5 or greater in Knight ADRC and by consensus committee review in the other cohorts. Clinical raters were blind to imaging, genetic, and fluid biomarker data. A secondary outcome was cognitive decline, based on a slope greater than 1.5 SD below the mean of an independent subsample of individuals without cognitive impairment. Outcomes were compared across the biomarker groups. RESULTS: Among 580 participants (PREVENT-AD, 128; HABS, 153; AIBL, 48; Knight ADRC, 251), mean (SD) age ranged from 67 (5) to 76 (6) years across cohorts, with between 55% (137/251) and 74% (95/128) female participants. Across cohorts, 33% to 83% of A+T+ participants progressed to MCI during follow-up (mean progression time, 2-2.72 years), compared with less than 20% of participants in other biomarker groups. Progression further increased to 43% to 100% when restricted to A+T+(N+) individuals. Cox proportional hazard ratios for progression to MCI in the A+T+ group vs other biomarker groups were all 5 or greater. Many A+T+ nonprogressors also showed longitudinal cognitive decline, while cognitive trajectories in other groups remained predominantly stable. CONCLUSIONS AND RELEVANCE: The clinical prognostic value of NIA-AA research criteria was confirmed in 4 independent cohorts, with most A+T+(N+) older individuals without cognitive impairment developing AD symptoms within 2 to 3 years.
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ItemCerebrospinal fluid levels of fatty acid-binding protein 3 are associated with likelihood of amyloidopathy in cognitively healthy individuals(WILEY, 2022)INTRODUCTION: Fatty acid-binding protein 3 (FABP3) is a biomarker of neuronal membrane disruption, associated with lipid dyshomeostasis-a notable Alzheimer's disease (AD) pathophysiological change. We assessed the association of cerebrospinal fluid (CSF) FABP3 levels with brain amyloidosis and the likelihood/risk of developing amyloidopathy in cognitively healthy individuals. METHODS: FABP3 levels were measured in CSF samples of cognitively healthy participants, > 60 years of age (n = 142), from the Australian Imaging, Biomarkers & Lifestyle Flagship Study of Ageing (AIBL). RESULTS: FABP3 levels were positively associated with baseline brain amyloid beta (Aβ) load as measured by standardized uptake value ratio (SUVR, standardized β = 0.22, P = .009) and predicted the change in brain Aβ load (standardized β = 0.32, P = .004). Higher levels of CSF FABP3 (above median) were associated with a likelihood of amyloidopathy (odds ratio [OR] 2.28, 95% confidence interval [CI] 1.12 to 4.65, P = .023). DISCUSSION: These results support inclusion of CSF FABP3 as a biomarker in risk-prediction models of AD.