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Total 793 results found since Jan 2013.

Minimal sufficient balance--a new strategy to balance baseline covariates and preserve randomness of treatment allocation
In many clinical trials, baseline covariates could affect the primary outcome. Commonly used strategies to balance baseline covariates include stratified constrained randomization and minimization. Stratification is limited to few categorical covariates. Minimization lacks the randomness of treatment allocation. Both apply only to categorical covariates. As a result, serious imbalances could occur in important baseline covariates not included in the randomization algorithm. Furthermore, randomness of treatment allocation could be significantly compromised because of the high proportion of deterministic assignments associat...
Source: Statistical Methods in Medical Research - November 26, 2015 Category: Statistics Authors: Zhao, W., Hill, M. D., Palesch, Y. Tags: Articles Source Type: research

The choice of prior distribution for a covariance matrix in multivariate meta‐analysis: a simulation study
Bayesian meta‐analysis is an increasingly important component of clinical research, with multivariate meta‐analysis a promising tool for studies with multiple endpoints. Model assumptions, including the choice of priors, are crucial aspects of multivariate Bayesian meta‐analysis (MBMA) models. In a given model, two different prior distributions can lead to different inferences about a particular parameter. A simulation study was performed in which the impact of families of prior distributions for the covariance matrix of a multivariate normal random effects MBMA model was analyzed. Inferences about effect sizes were ...
Source: Statistics in Medicine - August 24, 2015 Category: Statistics Authors: Sandra M. Hurtado Rúa, Madhu Mazumdar, Robert L. Strawderman Tags: Research Article Source Type: research

Leveraging prognostic baseline variables to gain precision in randomized trials
We focus on estimating the average treatment effect in a randomized trial. If baseline variables are correlated with the outcome, then appropriately adjusting for these variables can improve precision. An example is the analysis of covariance (ANCOVA) estimator, which applies when the outcome is continuous, the quantity of interest is the difference in mean outcomes comparing treatment versus control, and a linear model with only main effects is used. ANCOVA is guaranteed to be at least as precise as the standard unadjusted estimator, asymptotically, under no parametric model assumptions and also is locally semiparametric ...
Source: Statistics in Medicine - April 15, 2015 Category: Statistics Authors: Elizabeth Colantuoni, Michael Rosenblum Tags: Research Article Source Type: research

Surveillance of cardiovascular diseases using a multivariate dynamic screening system
In the SHARe Framingham Heart Study of the National Heart, Lung and Blood Institute, one major task is to monitor several health variables (e.g., blood pressure and cholesterol level) so that their irregular longitudinal pattern can be detected as soon as possible and some medical treatments applied in a timely manner to avoid some deadly cardiovascular diseases (e.g., stroke). To handle this kind of applications effectively, we propose a new statistical methodology called multivariate dynamic screening system (MDySS) in this paper. The MDySS method combines the major strengths of the multivariate longitudinal data analysi...
Source: Statistics in Medicine - March 11, 2015 Category: Statistics Authors: Peihua Qiu, Dongdong Xiang Tags: Research Article Source Type: research

Mathematical model of the effect of ischemia-reperfusion on brain capillary collapse and tissue swelling.
Abstract Restoration of an adequate cerebral blood supply after an ischemic attack is a primary clinical goal. However, the blood-brain barrier may break down after a prolonged ischemia causing the fluid in the blood plasma to filtrate and accumulate into the cerebral tissue interstitial space. Accumulation of this filtration fluid causes the cerebral tissue to swell, a condition known as vasogenic oedema. Tissue swelling causes the cerebral microvessels to be compressed, which may further obstruct the blood flow into the tissue, thus leading to the no-reflow phenomenon or a secondary ischemic stroke. The actual m...
Source: Mathematical Biosciences - March 3, 2015 Category: Statistics Authors: Mohamed Mokhtarudin MJ, Payne SJ Tags: Math Biosci Source Type: research

Evaluating hospital performance based on excess cause‐specific incidence
Formal evaluation of hospital performance in specific types of care is becoming an indispensable tool for quality assurance in the health care system. When the prime concern lies in reducing the risk of a cause‐specific event, we propose to evaluate performance in terms of an average excess cumulative incidence, referring to the center's observed patient mix. Its intuitive interpretation helps give meaning to the evaluation results and facilitates the determination of important benchmarks for hospital performance. We apply it to the evaluation of cerebrovascular deaths after stroke in Swedish stroke centers, using data f...
Source: Statistics in Medicine - January 16, 2015 Category: Statistics Authors: Bart Van Rompaye, Marie Eriksson, Els Goetghebeur Tags: Research Article Source Type: research

National hospital discharge survey: 2006 annual summary
This report presents 2006 national estimates and selected trend data on the use of nonfederal short-stay hospitals in the United States. Estimates are provided by selected patient and hospital characteristics, diagnoses, and surgical and nonsurgical procedures performed. Estimates of diagnoses and procedures are presented according to the International Classification of Diseases, Ninth Revision, Clinical Modification codes. Methods-The estimates are based on data collected through the National Hospital Discharge Survey (NHDS). The survey has been conducted annually since 1965. In 2006, data were collected for approximately...
Source: Vital Health Statistics Series 13 - October 1, 2014 Category: Statistics Authors: Verita C Buie Maria F Owings Carol J DeFrances Alexander Golosinskiy Source Type: research