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Stochastic Variation In Network Epidemic Models: Implications For The Design Of Community Level Hiv Prevention Trials, David Boren, Patrick Sullivan, Chris Beyrer, Stefan Baral, Linda-Gail Becker, Ron Brookmeyer Sep 2014

Stochastic Variation In Network Epidemic Models: Implications For The Design Of Community Level Hiv Prevention Trials, David Boren, Patrick Sullivan, Chris Beyrer, Stefan Baral, Linda-Gail Becker, Ron Brookmeyer

Ron Brookmeyer

Important sources of variation in the spread of HIV in communities arise from overlapping sexual networks and heterogeneity in biological and behavioral risk factors in populations. These sources of variation are not routinely accounted for in the design of HIV prevention trials. In this paper, we use agent based models to account for these sources of variation. We illustrate the approach with an agent based model for the spread of HIV infection among men who have sex with men (MSM) in South Africa. We find that traditional sample size approaches that rely on binomial (or Poisson) models are inadequate and …


A Serial Risk Score Approach To Disease Classification That Accounts For Accuracy And Cost, Ron Brookmeyer, Dat Huynh, Oliver Laeyendecker Dec 2013

A Serial Risk Score Approach To Disease Classification That Accounts For Accuracy And Cost, Ron Brookmeyer, Dat Huynh, Oliver Laeyendecker

Ron Brookmeyer

The performance of diagnostic tests for disease classification is often measured by accuracy (e.g., sensitivity or specificity); however, costs of the diagnostic test are a concern as well. Combinations of multiple diagnostic tests may improve accuracy, but incur additional costs. Here, we consider serial testing approaches that maintain accuracy while controlling costs of the diagnostic tests. We present a serial risk score classification approach. The basic idea is to sequentially test with additional diagnostic tests just until persons are classified. In this way, it is not necessary to test all persons with all tests. The methods are studied in simulations …


Cross-Sectional Hiv Incidence Estimation In Hiv Prevention Research, Ron Brookmeyer, Oliver Laeyendecker, Deborah Donnell, Susan H. Eshleman Dec 2012

Cross-Sectional Hiv Incidence Estimation In Hiv Prevention Research, Ron Brookmeyer, Oliver Laeyendecker, Deborah Donnell, Susan H. Eshleman

Ron Brookmeyer

Accurate methods for estimating HIV incidence from cross-sectional samples would have great utility in prevention research. This report describes recent improvements in cross-sectional methods that significantly improve their accuracy. These improvements are based on the use of multiple biomarkers to identify recent HIV infections. These multiassay algorithms (MAAs) use assays in a hierarchical approach for testing that minimizes the effort and cost of incidence estimation. These MAAs do not require mathematical adjustments for accurate estimation of the incidence rates in study populations in the year before sample collection. MAAs provide a practical, accurate, and cost-effective approach for cross-sectional HIV incidence …


National Estimates Of The Prevalence Of Alzheimer's Disease In The United States, Ron Brookmeyer, Denis Evans, Liesi Hebert, Langa Kenneth, Heeringa Steven, Plassman Brenda, Kukull Kenneth Dec 2010

National Estimates Of The Prevalence Of Alzheimer's Disease In The United States, Ron Brookmeyer, Denis Evans, Liesi Hebert, Langa Kenneth, Heeringa Steven, Plassman Brenda, Kukull Kenneth

Ron Brookmeyer

Several methods of estimating prevalence of dementia are presented in this article. For both Brookmeyer and the Chicago Health and Aging project (CHAP), the estimates of prevalence are derived statistically, forward calculating from incidence and survival figures. The choice of incidence rates on which to build the estimates may be critical. Brookmeyer used incidence rates from several published studies, whereas the CHAP investigators applied the incidence rates observed in their own cohort. The Aging, Demographics, and Memory Study (ADAMS) and the East Boston Senior Health Project (EBSHP) were sample surveys designed to ascertain the prevalence of Alzheimer’s disease and dementia. …


Statistical Considerations In Determining Hiv Incidence From Changes In Hiv Prevalence, Ron Brookmeyer, Jacob Konikoff Dec 2010

Statistical Considerations In Determining Hiv Incidence From Changes In Hiv Prevalence, Ron Brookmeyer, Jacob Konikoff

Ron Brookmeyer

The development of methods for estimating HIV incidence is critical for tracking the epidemic and for designing, targeting and evaluating HIV prevention efforts. One method for estimating incidence is based on changes in HIV prevalence. That method is attracting increased attention because national population-based HIV prevalence surveys, such as Demographic and Health Surveys, are being conducted throughout the world. Here, we consider some statistical issues associated with estimating HIV incidence from two population-based HIV prevalence surveys conducted at two different points in time. We show that the incidence estimator depends on the relative survival rate. We evaluate the sensitivity of …


On The Statistical Accuracy Of Biomarker Assays Of Hiv Incidence, Ron Brookmeyer Dec 2009

On The Statistical Accuracy Of Biomarker Assays Of Hiv Incidence, Ron Brookmeyer

Ron Brookmeyer

Objective: To evaluate the statistical accuracy of estimates of current HIV incidence rates from cross-sectional surveys, and to identify characteristics of assays that improve accuracy.

Methods: Performed mathematical and statistical analysis of the cross-sectional estimator of HIV incidence to evaluate bias and variance. Developed probability models to evaluate impact of long tails of the window period distribution on accuracy.

Results: The standard cross-sectional estimate of HIV incidence rate is estimating a time-lagged incidence where the lag time, called the shadow, depends on the mean and the coefficient of variation of window periods. Equations show how the shadow increases with the …


Should Biomarker Estimates Of Hiv Incidence Be Adjusted?, Ron Brookmeyer Dec 2008

Should Biomarker Estimates Of Hiv Incidence Be Adjusted?, Ron Brookmeyer

Ron Brookmeyer

Objective: To evaluate adjustment procedures that have been proposed to correct HIV incidence rates derived from cross-sectional surveys of biomarkers (BED). These procedures were motivated by some reports that the biomarker BED approach overestimates incidence when compared to cohort studies.

Design: Considered the Hargrove and McDougal adjustment procedures that adjust biomarker estimates of HIV incidence rates for misclassification with respect to the timing of infections.

Methods: Performed mathematical and statistical analysis of the adjustment formulas. Evaluated sources of error in cohort studies of incidence that could also explain discrepancies between cohort and biomarker estimates.

Results: The McDougal adjustment has no …


The Effects Of Herd Immunity On The Power Of Vaccine Trials, Blake Charvat, Ron Brookmeyer, Jay Herson Dec 2008

The Effects Of Herd Immunity On The Power Of Vaccine Trials, Blake Charvat, Ron Brookmeyer, Jay Herson

Ron Brookmeyer

We evaluate the effects of herd immunity on the power of vaccine trials. We consider large-scale trials in which persons are individually randomized to either placebo or vaccine. We evaluate the adequacy of naive power calculations that ignore the effects of herd immunity such as those based on the comparison of two independent binomials. We developed a simulation design to evaluate the quantitative effects of herd immunity on power. The simulation design accounted for nonhomogeneous mixing. We found that naive power calculations that ignore the effects of herd immunity can seriously overestimate power. In fact, we found that as sample …


Modeling The Effect Of Alzheimer's Disease On Mortality, Elizabeth Johnson, Ron Brookmeyer, Kathryn Ziegler-Graham Dec 2006

Modeling The Effect Of Alzheimer's Disease On Mortality, Elizabeth Johnson, Ron Brookmeyer, Kathryn Ziegler-Graham

Ron Brookmeyer

Mortality rate ratios and the associated proportional hazards models have been used to summarize the effect of Alzheimer's disease on longevity. However, the mortality rate ratios vary by age and therefore do not provide a simple parsimonious summary of the effect of the disease on lifespan. Instead, we propose a new parameter that is defined by an additive multistate model. The proposed multistate model accounts for different stages of disease progression. The underlying assumption of the model is that the effect of disease on mortality is to add a constant amount to death rates once the disease progresses from an …


Modeling The Incubation Period Of Anthrax, Ron Brookmeyer, Elizabeth Johnson, Sarah Barry Dec 2006

Modeling The Incubation Period Of Anthrax, Ron Brookmeyer, Elizabeth Johnson, Sarah Barry

Ron Brookmeyer

Models of the incubation period of anthrax are important to public health planners because they can be used to predict the delay before outbreaks are detected, the size of an outbreak and the duration of time that persons should remain on antibiotics to prevent disease. The difficulty is that there is little direct data about the incubation period in humans. The objective of this paper is to develop and apply models for the incubation period of anthrax. Mechanistic models that account for the biology of spore clearance and germination are developed based on a competing risks formulation. The models predict …


Modeling An Outbreak Of Anthrax, Ron Brookmeyer Nov 2006

Modeling An Outbreak Of Anthrax, Ron Brookmeyer

Ron Brookmeyer

Introduction

On October 2, 2001 a sixty-three-year-old Florida man who worked as a photo editor at a media publishing company was admitted to an emergency department complaining of nausea, vomiting, and fever. His symptoms began four days earlier on a recreational trip to North Carolina. The man died shortly thereafter. An astute clinician quickly made the surprising diagnosis of inhalational anthrax, which is a serious and deadly disease. The diagnosis was surprising because inhalational anthrax is extremely rare; only 18 cases were reported in the United States between 1900 and 1978. Public health officials at first believed that the Florida …


Biosecurity And The Role Of Statisticians, Ron Brookmeyer Nov 2005

Biosecurity And The Role Of Statisticians, Ron Brookmeyer

Ron Brookmeyer

No abstract provided.


Aging And The Public Health Impact Of Dementia, Ron Brookmeyer, Claudia Kawas Nov 2001

Aging And The Public Health Impact Of Dementia, Ron Brookmeyer, Claudia Kawas

Ron Brookmeyer

No abstract provided.