258 research outputs found
The Bayesian Analysis of Complex, High-Dimensional Models: Can It Be CODA?
We consider the Bayesian analysis of a few complex, high-dimensional models
and show that intuitive priors, which are not tailored to the fine details of
the model and the estimated parameters, produce estimators which perform poorly
in situations in which good, simple frequentist estimators exist. The models we
consider are: stratified sampling, the partial linear model, linear and
quadratic functionals of white noise and estimation with stopping times. We
present a strong version of Doob's consistency theorem which demonstrates that
the existence of a uniformly -consistent estimator ensures that the
Bayes posterior is -consistent for values of the parameter in subsets
of prior probability 1. We also demonstrate that it is, at least, in principle,
possible to construct Bayes priors giving both global and local minimax rates,
using a suitable combination of loss functions. We argue that there is no
contradiction in these apparently conflicting findings.Comment: Published in at http://dx.doi.org/10.1214/14-STS483 the Statistical
Science (http://www.imstat.org/sts/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Charting the complete elastic properties of inorganic crystalline compounds
The elastic constant tensor of an inorganic compound provides a complete description of the response of the material to external stresses in the elastic limit. It thus provides fundamental insight into the nature of the bonding in the material, and it is known to correlate with many mechanical properties. Despite the importance of the elastic constant tensor, it has been measured for a very small fraction of all known inorganic compounds, a situation that limits the ability of materials scientists to develop new materials with targeted mechanical responses. To address this deficiency, we present here the largest database of calculated elastic properties for inorganic compounds to date. The database currently contains full elastic information for 1,181 inorganic compounds, and this number is growing steadily. The methods used to develop the database are described, as are results of tests that establish the accuracy of the data. In addition, we document the database format and describe the different ways it can be accessed and analyzed in efforts related to materials discovery and design
Effect of Chronic Kidney Diseases on Mortality among Digoxin Users Treated for Non-Valvular Atrial Fibrillation: A Nationwide Register-Based Retrospective Cohort Study.
PURPOSE: This study investigated the impact of chronic kidney disease on all-causes and cardiovascular mortality in patients with atrial fibrillation treated with digoxin. METHODS: All patients with non-valvular atrial fibrillation and/or atrial flutter as hospitalization diagnosis from January 1, 1997 to December 31, 2012 were identified in Danish nationwide administrative registries. Cox proportional hazard model was used to compare the adjusted risk of all-causes and cardiovascular mortality among patients with and without chronic kidney disease and among patients with different chronic kidney disease stages within 180 days and 2 years from the first digoxin prescription. RESULTS: We identified 37,981 patients receiving digoxin; 1884 patients had the diagnosis of chronic kidney disease. Cox regression analysis showed no statistically significant differences in all-causes (Hazard Ratio, HR 0.89; 95% confident interval, CI 0.78-1.03) and cardiovascular mortality (HR 0.88; 95%CI 0.74-1.05) among patients with and without chronic kidney disease within 180 days of follow-up period. No statistically significant differences was found using a 2 years follow-up period neither for all causes mortality (HR 0.90; 95%CI 0.79-1.03), nor for cardiovascular mortality (HR 0.87; 95%CI 0.74-1.02). No statistically significant differences was found comparing patients with and without estimated Glomerular Filtration Rate <30ml/min/1.73m2 and patients with different stages of chronic kidney disease, for all-causes and cardiovascular mortality within 180 days and 2 years from the first digoxin prescription. CONCLUSIONS: This study suggest no direct effect of chronic kidney disease and chronic kidney disease stages on all-causes and cardiovascular mortality within both 180 days and 2 years from the first digoxin prescription in patients treatment-naïve with digoxin for non-valvular atrial fibrillation
Assessment of Application Technology of Natural User Interfaces in the Creation of a Virtual Chemical Laboratory
The Impact of Moving from EQ-5D-3L to -5L in NICE Technology Appraisals
Background: The EuroQol-5 Dimension (EQ-5D) instrument is the National Institute for Health and Care Excellence (NICE)’s preferred measure of health-related quality of life (QoL) in adults. The three-level (3L) value set is currently recommended for use, but the five-level (5L) set is increasingly being used in practice. Objective: We aimed to explore the impact of moving from 3L to 5L in NICE appraisals. Methods: We adapted our existing mapping for use with health state utility values derived from a population where the original distribution of utilities was unknown. We used this mapping to estimate 5L utilities for 21 comparisons of interventions from models used in NICE technology appraisal decision making, covering a range of disease areas. Results: All utilities increased using 5L, and the differences between highest and lowest utilities decreased. In ten oncology comparisons, using 5L generally increased the incremental quality-adjusted life-years (QALYs) as the benefit from improving survival increased. In four non-oncology comparisons where the intervention improved QoL only, the incremental QALYs decreased as the benefit of improving QoL was reduced. In seven non-oncology comparisons where interventions improved survival and QoL, there was a trade-off between increasing the benefit from survival and decreasing the benefit from improving QoL. Conclusion: 3L and 5L lead to substantially different estimates of incremental QALYs and cost effectiveness. The direction and magnitude of the change is not consistent across case studies. Using 5L instead of 3L may lead to different reimbursement decisions. NICE will face inconsistencies in decision making if it uses 3L and 5L concurrently
A multicenter assessment of interreader reliability of LI-RADS version 2018 for MRI and CT
Background: Various limitations have impacted research evaluating reader agreement
for Liver Imaging-Reporting and Data System (LI-RADS).
Purpose: To assess reader agreement of LI-RADS in an international multi-center, multireader setting using scrollable images.
Materials and Methods: This retrospective study used de-identified clinical multiphase
CT and MRI examinations and reports with at least one untreated observation from six
institutions and three countries; only qualifying examinations were submitted.
Examination dates were October 2017 – August 2018 at the coordinating center. One
untreated observation per examination was randomly selected using observation
identifiers, and its clinically assigned features were extracted from the report. The
corresponding LI-RADS v2018 category was computed as a re-scored clinical read. Each
examination was randomly assigned to two of 43 research readers who independently
scored the observation. Agreement for an ordinal modified four-category LI-RADS scale
(LR-1/2, LR-3, LR-4, LR-5/M/tumor in vein) was computed using intra-class correlation
coefficients (ICC). Agreement was also computed for dichotomized malignancy (LR-4/LR5/LR-M/LR-tumor in vein), LR-5, and LR-M. Agreement was compared between researchversus-research reads and research-versus-clinical reads.
Results: 484 patients (mean age, 62 years ±10 [SD]; 156 women; 93 CT, 391 MRI) were
included. ICCs for ordinal LI-RADS, dichotomized malignancy, LR-5, and LR-M were 0.68
(95% CI: 0.62, 0.74), 0.63 (95% CI: 0.56, 0.71), 0.58 (95% CI: 0.50, 0.66), and 0.46 (95%
CI: 0.31, 0.61) respectively. Research-versus-research reader agreement was higher
than research-versus-clinical agreement for modified four-category LI-RADS (ICC, 0.68
vs. 0.62, P = .03) and for dichotomized malignancy (ICC, 0.63 vs. 0.53, P = .005), but not
for LR-5 (P = .14) or LR-M (P = .94).
Conclusion: There was moderate agreement for Liver Imaging-Reporting and Data
System v2018 overall. For some comparisons, research-versus-research reader
agreement was higher than research-versus-clinical reader agreement, indicating
differences between the clinical and research environments that warrant further study
HIV-associated neurocognitive disorders before and during the era of combination antiretroviral therapy: differences in rates, nature, and predictors
Combination antiretroviral therapy (CART) has greatly reduced medical morbidity and mortality with HIV infection, but high rates of HIV-associated neurocognitive disorders (HAND) continue to be reported. Because large HIV-infected (HIV+) and uninfected (HIV−) groups have not been studied with similar methods in the pre-CART and CART eras, it is unclear whether CART has changed the prevalence, nature, and clinical correlates of HAND. We used comparable methods of subject screening and assessments to classify neurocognitive impairment (NCI) in large groups of HIV + and HIV − participants from the pre-CART era (1988–1995; N = 857) and CART era (2000–2007; N = 937). Impairment rate increased with successive disease stages (CDC stages A, B, and C) in both eras: 25%, 42%, and 52% in pre-CART era and 36%, 40%, and 45% in CART era. In the medically asymptomatic stage (CDC-A), NCI was significantly more common in the CART era. Low nadir CD4 predicted NCI in both eras, whereas degree of current immunosuppression, estimated duration of infection, and viral suppression in CSF (on treatment) were related to impairment only pre-CART. Pattern of NCI also differed: pre-CART had more impairment in motor skills, cognitive speed, and verbal fluency, whereas CART era involved more memory (learning) and executive function impairment. High rates of mild NCI persist at all stages of HIV infection, despite improved viral suppression and immune reconstitution with CART. The consistent association of NCI with nadir CD4 across eras suggests that earlier treatment to prevent severe immunosuppression may also help prevent HAND. Clinical trials targeting HAND prevention should specifically examine timing of ART initiation
Graphical methods for multivariate linear models in psychological research: An R tutorial
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