Download or read book Evaluating New Matrix Pooled Testing Methods for Detecting HIV Treatment Failure with and Without Covariate Information written by Adam Brand and published by . This book was released on 2016 with total page 83 pages. Available in PDF, EPUB and Kindle. Book excerpt: University of Washington Abstract Evaluating New Matrix Pooled Testing Methods for Detecting HIV Treatment Failure with and without Covariate Information Adam Brand Chair of the Supervisory Committee: Susanne May, Associate Professor Department of Biostatistics Antiretroviral treatment for HIV has proven to lengthen and improve patients’ lives, and greatly reduce the risk of transmission. Patients receiving antiretroviral treatment for HIV must be monitored for treatment failure, so the treatment regimen can be altered to maintain low HIV viral load levels. Monitoring/testing treated HIV patients requires resources not available to resource-limited regions most in need. It has been shown that matrix pooled testing can be efficient compared to individual testing under certain conditions however, further improvements are needed. The current best-performing matrix pooled testing method for detecting HIV treatment failure does not use covariate information. Other methods which do use covariate information have not yet been shown to outperform this method in settings with realistic, skewed viral load values. We propose new methods of matrix pooled testing, some of which use covariate information, and evaluate method performance with respect to relative efficiency, sensitivity and number of testing rounds. Based on simulation results we identify a method which incorporates covariate information and outperforms the current best-performing method in settings using realistic, skewed viral load values when we have access to a predictor(s) of virologic failure.
Download or read book Biostatistical Methods for HIV Monitoring and Prevention written by Brett S. Hanscom and published by . This book was released on 2014 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pooled-testing methods can greatly reduce the number of tests needed to identify failures in a collection of samples. Existing methodology has focused primarily on binary tests, but there is a clear need for improved efficiency when using expensive quantitative tests, such as tests for HIV viral load in resource-limited settings. We propose a matrix-pooling method which uses the EM algorithm to identify individual samples most likely to be failures. Simulation studies show that the proposed method can improve testing efficiency by a modest amount, and dramatically reduce the total number of testing rounds needed to identify all failures. In settings where the turn-around time for testing services is significant, the EM method can substantial time savings. The EM method does not perform as well when the measurements of interest are highly skewed, as is often the case with viral load concentrations. We therefore propose a second method that accommodates situations where target quantities do not follow a normal distribution. This approach uses Markov Chain Monte Carlo (MCMC) sampling to identify the failure status of individual samples, and is highly flexible in terms of assumptions regarding the distributions of both target quantities and measurement error. This method is further extended to include covariate information. Simulation studies show that the proposed method can substantially reduce turn-around time as compared to existing group-testing methods, particularly when covariate data is available that are highly predictive of failure. The proposed method did not perform as well when applied to a series of real datasets taken from actual pooled specimens. This may be due to measurement error variances for viral load testing that are much higher than anticipated. Discordant partner studies are commonly used to quantify per-act infectivity rates for HIV. Statistical models used to estimate these rates depend on self-reported sexual activity, which is notoriously unreliable. The degree to which misreported sexual activity can affect infectivity estimates has not previously been reported. By using a basic transmission model in the context of measurement error, we show that infectivity estimates can be severely biased, and that the size and direction of bias depends on the underlying infectivity rate and on the mean number of sex acts occurring in the observation window. We show that by modifying the size of this window, in certain circumstances it is possible to avoid measurement-error bias without having to use a more sophisticated statistical model. We also show that, when misreporting is ignored, covariate parameter estimates can be biased, particularly when subgroup differences are large or when sexual frequency is heterogeneous. Recent discordant partner studies have begun collecting sexual history data from both partners. We propose a latent-variable transmission model which incorporates data from both partners, and accounts for the mis-reporting of sex acts as well as non-overlapping recall periods. Bayes-MCMC methods are used to generate parameter estimates. Simulation studies demonstrate that the proposed method can dramatically reduce measurement-error bias for per-act infectivity estimation. We then apply this method to the Partners PrEP study dataset and show that HIV infectivity may be 25% higher than would be estimated with a naive model.
Download or read book Guidelines on Hepatitis B and C Testing written by World Health Organization and published by World Health Organization. This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Testing and diagnosis of hepatitis B (HBV) and C (HCV) infection is the gateway for access to both prevention and treatment services, and is a crucial component of an effective response to the hepatitis epidemic. Early identification of persons with chronic HBV or HCV infection enables them to receive the necessary care and treatment to prevent or delay progression of liver disease. Testing also provides an opportunity to link people to interventions to reduce transmission, through counselling on risk behaviors and provision of prevention commodities (such as sterile needles and syringes) and hepatitis B vaccination. These are the first WHO guidelines on testing for chronic HBV and HCV infection and complement published guidance by WHO on the prevention, care and treatment of chronic hepatitis C and hepatitis B infection. These guidelines outline the public health approach to strengthening and expanding current testing practices for HBV and HCV, and are intended for use across age groups and populations.
Download or read book Registries for Evaluating Patient Outcomes written by Agency for Healthcare Research and Quality/AHRQ and published by Government Printing Office. This book was released on 2014-04-01 with total page 385 pages. Available in PDF, EPUB and Kindle. Book excerpt: This User’s Guide is intended to support the design, implementation, analysis, interpretation, and quality evaluation of registries created to increase understanding of patient outcomes. For the purposes of this guide, a patient registry is an organized system that uses observational study methods to collect uniform data (clinical and other) to evaluate specified outcomes for a population defined by a particular disease, condition, or exposure, and that serves one or more predetermined scientific, clinical, or policy purposes. A registry database is a file (or files) derived from the registry. Although registries can serve many purposes, this guide focuses on registries created for one or more of the following purposes: to describe the natural history of disease, to determine clinical effectiveness or cost-effectiveness of health care products and services, to measure or monitor safety and harm, and/or to measure quality of care. Registries are classified according to how their populations are defined. For example, product registries include patients who have been exposed to biopharmaceutical products or medical devices. Health services registries consist of patients who have had a common procedure, clinical encounter, or hospitalization. Disease or condition registries are defined by patients having the same diagnosis, such as cystic fibrosis or heart failure. The User’s Guide was created by researchers affiliated with AHRQ’s Effective Health Care Program, particularly those who participated in AHRQ’s DEcIDE (Developing Evidence to Inform Decisions About Effectiveness) program. Chapters were subject to multiple internal and external independent reviews.
Download or read book Scale Development written by Robert F. DeVellis and published by SAGE Publications. This book was released on 2016-03-30 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the Fourth Edition of Scale Development, Robert F. DeVellis demystifies measurement by emphasizing a logical rather than strictly mathematical understanding of concepts. The text supports readers in comprehending newer approaches to measurement, comparing them to classical approaches, and grasping more clearly the relative merits of each. This edition addresses new topics pertinent to modern measurement approaches and includes additional exercises and topics for class discussion. Available with Perusall—an eBook that makes it easier to prepare for class Perusall is an award-winning eBook platform featuring social annotation tools that allow students and instructors to collaboratively mark up and discuss their SAGE textbook. Backed by research and supported by technological innovations developed at Harvard University, this process of learning through collaborative annotation keeps your students engaged and makes teaching easier and more effective. Learn more.
Download or read book Public Health Service Publication written by and published by . This book was released on with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Econometric Analysis of Cross Section and Panel Data second edition written by Jeffrey M. Wooldridge and published by MIT Press. This book was released on 2010-10-01 with total page 1095 pages. Available in PDF, EPUB and Kindle. Book excerpt: The second edition of a comprehensive state-of-the-art graduate level text on microeconometric methods, substantially revised and updated. The second edition of this acclaimed graduate text provides a unified treatment of two methods used in contemporary econometric research, cross section and data panel methods. By focusing on assumptions that can be given behavioral content, the book maintains an appropriate level of rigor while emphasizing intuitive thinking. The analysis covers both linear and nonlinear models, including models with dynamics and/or individual heterogeneity. In addition to general estimation frameworks (particular methods of moments and maximum likelihood), specific linear and nonlinear methods are covered in detail, including probit and logit models and their multivariate, Tobit models, models for count data, censored and missing data schemes, causal (or treatment) effects, and duration analysis. Econometric Analysis of Cross Section and Panel Data was the first graduate econometrics text to focus on microeconomic data structures, allowing assumptions to be separated into population and sampling assumptions. This second edition has been substantially updated and revised. Improvements include a broader class of models for missing data problems; more detailed treatment of cluster problems, an important topic for empirical researchers; expanded discussion of "generalized instrumental variables" (GIV) estimation; new coverage (based on the author's own recent research) of inverse probability weighting; a more complete framework for estimating treatment effects with panel data, and a firmly established link between econometric approaches to nonlinear panel data and the "generalized estimating equation" literature popular in statistics and other fields. New attention is given to explaining when particular econometric methods can be applied; the goal is not only to tell readers what does work, but why certain "obvious" procedures do not. The numerous included exercises, both theoretical and computer-based, allow the reader to extend methods covered in the text and discover new insights.
Download or read book Analysis of Observational Health Care Data Using SAS written by Douglas E. Faries and published by SAS Press. This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book guides researchers in performing and presenting high-quality analyses of all kinds of non-randomized studies, including analyses of observational studies, claims database analyses, assessment of registry data, survey data, pharmaco-economic data, and many more applications. The text is sufficiently detailed to provide not only general guidance, but to help the researcher through all of the standard issues that arise in such analyses. Just enough theory is included to allow the reader to understand the pros and cons of alternative approaches and when to use each method. The numerous contributors to this book illustrate, via real-world numerical examples and SAS code, appropriate implementations of alternative methods. The end result is that researchers will learn how to present high-quality and transparent analyses that will lead to fair and objective decisions from observational data. This book is part of the SAS Press program.
Download or read book Statistical Methods in Water Resources written by D.R. Helsel and published by Elsevier. This book was released on 1993-03-03 with total page 539 pages. Available in PDF, EPUB and Kindle. Book excerpt: Data on water quality and other environmental issues are being collected at an ever-increasing rate. In the past, however, the techniques used by scientists to interpret this data have not progressed as quickly. This is a book of modern statistical methods for analysis of practical problems in water quality and water resources.The last fifteen years have seen major advances in the fields of exploratory data analysis (EDA) and robust statistical methods. The 'real-life' characteristics of environmental data tend to drive analysis towards the use of these methods. These advances are presented in a practical and relevant format. Alternate methods are compared, highlighting the strengths and weaknesses of each as applied to environmental data. Techniques for trend analysis and dealing with water below the detection limit are topics covered, which are of great interest to consultants in water-quality and hydrology, scientists in state, provincial and federal water resources, and geological survey agencies.The practising water resources scientist will find the worked examples using actual field data from case studies of environmental problems, of real value. Exercises at the end of each chapter enable the mechanics of the methodological process to be fully understood, with data sets included on diskette for easy use. The result is a book that is both up-to-date and immediately relevant to ongoing work in the environmental and water sciences.
Download or read book Proceedings written by and published by . This book was released on 1963 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Computers Electrocardiography and Public Health written by United States. Public Health Service and published by . This book was released on 1967 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Computers Electrocardiography and Public Health written by Medical Systems Development Laboratory and published by . This book was released on 1967 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Survival Analysis written by John P. Klein and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 508 pages. Available in PDF, EPUB and Kindle. Book excerpt: Making complex methods more accessible to applied researchers without an advanced mathematical background, the authors present the essence of new techniques available, as well as classical techniques, and apply them to data. Practical suggestions for implementing the various methods are set off in a series of practical notes at the end of each section, while technical details of the derivation of the techniques are sketched in the technical notes. This book will thus be useful for investigators who need to analyse censored or truncated life time data, and as a textbook for a graduate course in survival analysis, the only prerequisite being a standard course in statistical methodology.
Download or read book European Guidelines for Quality Assurance in Cervical Cancer Screening written by Marc Arbyn and published by . This book was released on 2008 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recoge: 1. Epidemiological guidelines for quality assurance in cervical cancer screening - 2. Methods for screening and diagnosis - 3. Laboratory guidelines and quality assurance practices for cytology - 4. Techniques and quality assurance guidelines for histopathology - 5. Management of abnormal cervical cytology - 6. Key performance indicators - 7. Annexes.
Download or read book Testing Structural Equation Models written by Kenneth A. Bollen and published by SAGE. This book was released on 1993-02 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt: What is the role of fit measures when respecifying a model? Should the means of the sampling distributions of a fit index be unrelated to the size of the sample? Is it better to estimate the statistical power of the chi-square test than to turn to fit indices? Exploring these and related questions, well-known scholars examine the methods of testing structural equation models (SEMS) with and without measurement error, as estimated by such programs as EQS, LISREL and CALIS.
Download or read book Data Acquisition and Processing in Biology and Medicine written by Kurt Enslein and published by . This book was released on 1964 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Pharmacokinetic Pharmacodynamic Modeling and Simulation written by Peter L. Bonate and published by Springer Science & Business Media. This book was released on 2011-07-01 with total page 634 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is a second edition to the original published by Springer in 2006. The comprehensive volume takes a textbook approach systematically developing the field by starting from linear models and then moving up to generalized linear and non-linear mixed effects models. Since the first edition was published the field has grown considerably in terms of maturity and technicality. The second edition of the book therefore considerably expands with the addition of three new chapters relating to Bayesian models, Generalized linear and nonlinear mixed effects models, and Principles of simulation. In addition, many of the other chapters have been expanded and updated.
