Scholars@Duke
Marie Davidian

Marie Davidian

Adjunct Professor of Biostatistics & Bioinformatics
Biostatistics & Bioinformatics, Division of Biostatistics
davidian@ncsu.edu
Duke Box 3850, Durham, NC 27710
247 Trent Dr, Durham, NC

Selected Publications

The eACT study design and methods: A sequential, multiple assignment, randomized trial of A novel adherence intervention for youth with epilepsy.

Journal Article Contemp Clin Trials · December 2024 BACKGROUND: Epilepsy is a common, chronic pediatric neurological condition predominately treated with anti-seizure medications (ASMs) to control or reduce seizures. Approximately 60 % of youth with epilepsy demonstrate suboptimal adherence to their ASM. Th ... Full text Link to item Cite

Estimation of optimal treatment regimes with electronic medical record data using the residual life value estimator.

Journal Article Biostatistics · October 1, 2024 Clinicians and patients must make treatment decisions at a series of key decision points throughout disease progression. A dynamic treatment regime is a set of sequential decision rules that return treatment decisions based on accumulating patient informat ... Full text Link to item Cite

Datopotamab-deruxtecan plus durvalumab in early-stage breast cancer: the sequential multiple assignment randomized I-SPY2.2 phase 2 trial.

Journal Article Nat Med · September 14, 2024 Sequential adaptive trial designs can help accomplish the goals of personalized medicine, optimizing outcomes and avoiding unnecessary toxicity. Here we describe the results of incorporating a promising antibody-drug conjugate, datopotamab-deruxtecan (Dato ... Full text Link to item Cite

Datopotamab-deruxtecan in early-stage breast cancer: the sequential multiple assignment randomized I-SPY2.2 phase 2 trial.

Journal Article Nat Med · September 14, 2024 Among the goals of patient-centric care are the advancement of effective personalized treatment, while minimizing toxicity. The phase 2 I-SPY2.2 trial uses a neoadjuvant sequential therapy approach in breast cancer to further these goals, testing promising ... Full text Link to item Cite

Interim monitoring of sequential multiple assignment randomized trials using partial information.

Journal Article Biometrics · December 2023 The sequential multiple assignment randomized trial (SMART) is the gold standard trial design to generate data for the evaluation of multistage treatment regimes. As with conventional (single-stage) randomized clinical trials, interim monitoring allows ear ... Full text Link to item Cite

A general framework for subgroup detection via one-step value difference estimation.

Journal Article Biometrics · September 2023 Recent statistical methodology for precision medicine has focused on either identification of subgroups with enhanced treatment effects or estimating optimal treatment decision rules so that treatment is allocated in a way that maximizes, on average, prede ... Full text Link to item Cite

Behavioral cancer pain intervention dosing: results of a Sequential Multiple Assignment Randomized Trial.

Journal Article Pain · September 1, 2023 Behavioral pain management interventions are efficacious for reducing pain in patients with cancer. However, optimal dosing of behavioral pain interventions for pain reduction is unknown, and this hinders routine clinical use. A Sequential Multiple Assignm ... Full text Link to item Cite

Cost-Effectiveness Analysis Evaluating Delivery Strategies for Pain Coping Skills Training in Women With Breast Cancer.

Journal Article J Pain · September 2023 Pain coping skills training (PCST) is efficacious in patients with cancer, but clinical access is limited. To inform implementation, as a secondary outcome, we estimated the cost-effectiveness of 8 dosing strategies of PCST evaluated in a sequential multip ... Full text Link to item Cite

DYNAMIC PREDICTION OF RESIDUAL LIFE WITH LONGITUDINAL COVARIATES USING LONG SHORT-TERM MEMORY NETWORKS.

Journal Article Ann Appl Stat · September 2023 Sepsis, a complex medical condition that involves severe infections with life-threatening organ dysfunction, is a leading cause of death worldwide. Treatment of sepsis is highly challenging. When making treatment decisions, clinicians and patients desire a ... Full text Link to item Cite

Estimation of the odds ratio in a proportional odds model with censored time-lagged outcome in a randomized clinical trial.

Journal Article Biometrics · June 2023 In many randomized clinical trials of therapeutics for COVID-19, the primary outcome is an ordinal categorical variable, and interest focuses on the odds ratio (OR; active agent vs control) under the assumption of a proportional odds model. Although at the ... Full text Link to item Cite

Group sequential methods for interim monitoring of randomized clinical trials with time-lagged outcome.

Journal Article Stat Med · December 10, 2022 The primary analysis in two-arm clinical trials usually involves inference on a scalar treatment effect parameter; for example, depending on the outcome, the difference of treatment-specific means, risk difference, risk ratio, or odds ratio. Most clinical ... Full text Link to item Cite

Estimating vaccine efficacy over time after a randomized study is unblinded.

Journal Article Biometrics · September 2022 The COVID-19 pandemic due to the novel coronavirus SARS CoV-2 has inspired remarkable breakthroughs in the development of vaccines against the virus and the launch of several phase 3 vaccine trials in Summer 2020 to evaluate vaccine efficacy (VE). Trials o ... Full text Link to item Cite

Methods Based on Semiparametric Theory for Analysis in the Presence of Missing Data

Journal Article Annual Review of Statistics and Its Application · March 7, 2022 A statistical model is a class of probability distributions assumed to contain the true distribution generating the data. In parametric models, the distributions are indexed by a finite-dimensional parameter characterizing the scientific question ... Full text Cite

Telehealth and racial disparities in colorectal cancer screening: A pilot study of how virtual clinician characteristics influence screening intentions.

Journal Article J Clin Transl Sci · 2022 INTRODUCTION: Racial disparities in colorectal cancer (CRC) can be addressed through increased adherence to screening guidelines. In real-life encounters, patients may be more willing to follow screening recommendations delivered by a race concordant clini ... Full text Link to item Cite

A Pilot Study Examining the Efficacy of Delivering Colorectal Cancer Screening Messages via Virtual Health Assistants.

Journal Article American journal of preventive medicine · August 2021 IntroductionPatients are more likely to complete colorectal cancer screening when recommended by a race-concordant healthcare provider. Leveraging virtual healthcare assistants to deliver tailored screening interventions may promote adherence to c ... Full text Cite

Sample Size Calculations for SMARTs

Journal Article · June 16, 2019 Sequential Multiple Assignment Randomized Trials (SMARTs) are considered the gold standard for estimation and evaluation of treatment regimes. SMARTs are typically sized to ensure sufficient power for a simple comparison, e.g., the comparison of two fixed ... Link to item Cite

Application of a sequential multiple assignment randomized trial (SMART) design in older patients with chronic lymphocytic leukemia.

Journal Article Ann Oncol · April 2019 BACKGROUND: Ibrutinib therapy is safe and effective in patients with chronic lymphocytic leukemia (CLL). Currently, ibrutinib is administered continuously until disease progression. Combination regimens with ibrutinib are being developed to deepen response ... Full text Link to item Cite

Optimal two-stage dynamic treatment regimes from a classification perspective with censored survival data.

Journal Article Biometrics · December 2018 Clinicians often make multiple treatment decisions at key points over the course of a patient's disease. A dynamic treatment regime is a sequence of decision rules, each mapping a patient's observed history to the set of available, feasible treatment optio ... Full text Link to item Cite

Report of the Editors-2017.

Journal Article Biometrics · March 2018 Full text Link to item Cite

Interpretable Dynamic Treatment Regimes.

Journal Article J Am Stat Assoc · 2018 Precision medicine is currently a topic of great interest in clinical and intervention science. A key component of precision medicine is that it is evidence-based, i.e., data-driven, and consequently there has been tremendous interest in estimation of prec ... Full text Link to item Cite

On Estimation of Optimal Treatment Regimes For Maximizing t-Year Survival Probability.

Journal Article J R Stat Soc Series B Stat Methodol · September 2017 A treatment regime is a deterministic function that dictates personalized treatment based on patients' individual prognostic information. There is increasing interest in finding optimal treatment regimes, which determine treatment at one or more treatment ... Full text Link to item Cite

Biometrics, JABES and the International Biometric Society

Journal Article Journal of Agricultural, Biological and Environmental Statistics · September 2017 Full text Cite

Dynamic treatment regimes, past, present, and future: A conversation with experts.

Journal Article Stat Methods Med Res · August 2017 We asked three leading researchers in the area of dynamic treatment regimes to share their stories on how they became interested in this topic and their perspectives on the most important opportunities and challenges for the future. ... Full text Link to item Cite

Optimizing delivery of a behavioral pain intervention in cancer patients using a sequential multiple assignment randomized trial SMART.

Journal Article Contemp Clin Trials · June 2017 BACKGROUND/AIMS: Pain is common in cancer patients and results in lower quality of life, depression, poor physical functioning, financial difficulty, and decreased survival time. Behavioral pain interventions are effective and nonpharmacologic. Traditional ... Full text Link to item Cite

Survival Benefit of Lung Transplantation in the Modern Era of Lung Allocation.

Journal Article Ann Am Thorac Soc · February 2017 RATIONALE: Lung transplantation is an accepted and increasingly employed treatment for advanced lung diseases, but the anticipated survival benefit of lung transplantation is poorly understood. OBJECTIVES: To determine whether and for which patients lung t ... Full text Link to item Cite

The analysis of multivariate longitudinal data: A review.

Journal Article Stat Methods Med Res · February 2017 Full text Link to item Cite

Using pilot data to size a two-arm randomized trial to find a nearly optimal personalized treatment strategy.

Journal Article Stat Med · April 15, 2016 A personalized treatment strategy formalizes evidence-based treatment selection by mapping patient information to a recommended treatment. Personalized treatment strategies can produce better patient outcomes while reducing cost and treatment burden. Thus, ... Full text Link to item Cite

Properties of Estimators in Exponential Family Settings with Observation-based Stopping Rules.

Journal Article J Biom Biostat · February 2016 Often, sample size is not fixed by design. A key example is a sequential trial with a stopping rule, where stopping is based on what has been observed at an interim look. While such designs are used for time and cost efficiency, and hypothesis testing theo ... Full text Link to item Cite

A Placebo-Controlled, Prospective, Randomized Clinical Trial of Polyethylene Glycol and Methylprednisolone Sodium Succinate in Dogs with Intervertebral Disk Herniation.

Journal Article J Vet Intern Med · 2016 BACKGROUND: Acute intervertebral disk herniation (IVDH) is a common cause of spinal cord injury in dogs and currently there is no proven medical treatment to counter secondary injury effects. Use of methylprednisolone sodium succinate (MPSS) or polyethylen ... Full text Link to item Cite

Using decision lists to construct interpretable and parsimonious treatment regimes.

Journal Article Biometrics · December 2015 A treatment regime formalizes personalized medicine as a function from individual patient characteristics to a recommended treatment. A high-quality treatment regime can improve patient outcomes while reducing cost, resource consumption, and treatment burd ... Full text Link to item Cite

Estimation After a Group Sequential Trial.

Journal Article Stat Biosci · October 2015 Group sequential trials are one important instance of studies for which the sample size is not fixed a priori but rather takes one of a finite set of pre-specified values, dependent on the observed data. Much work has been devoted to the inferential conseq ... Full text Link to item Cite

KAST Study: The Kiva System As a Vertebral Augmentation Treatment-A Safety and Effectiveness Trial: A Randomized, Noninferiority Trial Comparing the Kiva System With Balloon Kyphoplasty in Treatment of Osteoporotic Vertebral Compression Fractures.

Journal Article Spine (Phila Pa 1976) · June 15, 2015 STUDY DESIGN: The KAST (Kiva Safety and Effectiveness Trial) study was a pivotal, multicenter, randomized control trial for evaluation of safety and effectiveness in the treatment of patients with painful, osteoporotic vertebral compression fractures (VCFs ... Full text Link to item Cite

Report of the Editors—2014

Journal Article Biometrics · March 1, 2015 AbstractCo-Editors: Yi-Hau Chen (1 January 2014-31 December 2016)Michael J. Daniels (1 January 2015-31 December 2017)Jeanine Houwing-Duisterm ... Full text Cite

Response to reader reaction.

Journal Article Biometrics · March 2015 Full text Link to item Cite

Painful acute radiation thyroiditis induced by 131I treatment of Graves' disease.

Journal Article BMJ Case Rep · January 9, 2015 A 44-year-old woman, chronic smoker with Graves' disease was treated with radioactive iodine ablation (RAI). One week after the treatment, she presented with severe pain in the anterior neck with radiation to the angle of the jaw associated with fatigue, t ... Full text Link to item Cite

Q- and A-learning Methods for Estimating Optimal Dynamic Treatment Regimes.

Journal Article Stat Sci · November 2014 In clinical practice, physicians make a series of treatment decisions over the course of a patient's disease based on his/her baseline and evolving characteristics. A dynamic treatment regime is a set of sequential decision rules that operationalizes this ... Full text Link to item Cite

Report of the Editors—2013

Journal Article Biometrics · March 2014 Full text Cite

Preface

Book · March 1, 2014 Full text Cite

The analysis of multivariate longitudinal data: a review.

Journal Article Stat Methods Med Res · February 2014 Longitudinal experiments often involve multiple outcomes measured repeatedly within a set of study participants. While many questions can be answered by modeling the various outcomes separately, some questions can only be answered in a joint analysis of al ... Full text Link to item Cite

On random sample size, ignorability, ancillarity, completeness, separability, and degeneracy: sequential trials, random sample sizes, and missing data.

Journal Article Stat Methods Med Res · February 2014 The vast majority of settings for which frequentist statistical properties are derived assume a fixed, a priori known sample size. Familiar properties then follow, such as, for example, the consistency, asymptotic normality, and efficiency of the sample av ... Full text Link to item Cite

Collaboration to meet the statistical needs in the chemistry curriculum

Journal Article Journal of Chemical Education · January 14, 2014 Recent articles have recommended adding statistical topics to the chemistry curriculum. This letter to the editor recommends: (i) collaboration between statisticians and chemists; and (ii) emulating existing successful models to meet the statistical needs ... Full text Cite

SNP_NLMM: A SAS Macro to Implement a Flexible Random Effects Density for Generalized Linear and Nonlinear Mixed Models.

Journal Article J Stat Softw · January 1, 2014 Generalized linear and nonlinear mixed models (GMMMs and NLMMs) are commonly used to represent non-Gaussian or nonlinear longitudinal or clustered data. A common assumption is that the random effects are Gaussian. However, this assumption may be unrealisti ... Full text Link to item Cite

Assessing the causal effect of organ transplantation on the distribution of residual lifetime.

Journal Article Biometrics · December 2013 Because the number of patients waiting for organ transplants exceeds the number of organs available, a better understanding of how transplantation affects the distribution of residual lifetime is needed to improve organ allocation. However, there has been ... Full text Link to item Cite

Moment Adjusted Imputation for Multivariate Measurement Error Data with Applications to Logistic Regression.

Journal Article Comput Stat Data Anal · November 1, 2013 In clinical studies, covariates are often measured with error due to biological fluctuations, device error and other sources. Summary statistics and regression models that are based on mismeasured data will differ from the corresponding analysis based on t ... Full text Link to item Cite

The international year of statistics: A celebration and a call to action

Journal Article Journal of the American Statistical Association · January 1, 2013 Full text Cite

Robust estimation of optimal dynamic treatment regimes for sequential treatment decisions.

Journal Article Biometrika · 2013 A dynamic treatment regime is a list of sequential decision rules for assigning treatment based on a patient's history. Q- and A-learning are two main approaches for estimating the optimal regime, i.e., that yielding the most beneficial outcome in the pati ... Full text Link to item Cite

Variable selection for covariate-adjusted semiparametric inference in randomized clinical trials.

Journal Article Stat Med · December 20, 2012 Extensive baseline covariate information is routinely collected on participants in randomized clinical trials, and it is well recognized that a proper covariate-adjusted analysis can improve the efficiency of inference on the treatment effect. However, suc ... Full text Link to item Cite

A robust method for estimating optimal treatment regimes.

Journal Article Biometrics · December 2012 A treatment regime is a rule that assigns a treatment, among a set of possible treatments, to a patient as a function of his/her observed characteristics, hence "personalizing" treatment to the patient. The goal is to identify the optimal treatment regime ... Full text Link to item Cite

Dose Calibration

Other · August 31, 2012 Abstract Calibration refers broadly to the determination of a variable x on the basis of measurement(s) on another variable ... Full text Cite

Why statistics?

Journal Article Science · April 6, 2012 Full text Link to item Cite

Biometrics. Report of the editors--2011.

Journal Article Biometrics · March 2012 Full text Link to item Cite

Estimating Optimal Treatment Regimes from a Classification Perspective.

Journal Article Stat · January 1, 2012 A treatment regime maps observed patient characteristics to a recommended treatment. Recent technological advances have increased the quality, accessibility, and volume of patient-level data; consequently, there is a growing need for powerful and flexible ... Full text Link to item Cite

Mixed model analysis of censored longitudinal data with flexible random-effects density.

Journal Article Biostatistics · January 2012 Mixed models are commonly used to represent longitudinal or repeated measures data. An additional complication arises when the response is censored, for example, due to limits of quantification of the assay used. While Gaussian random effects are routinely ... Full text Link to item Cite

A moment-adjusted imputation method for measurement error models.

Journal Article Biometrics · December 2011 Studies of clinical characteristics frequently measure covariates with a single observation. This may be a mismeasured version of the "true" phenomenon due to sources of variability like biological fluctuations and device error. Descriptive analyses and ou ... Full text Link to item Cite

Timing of HAART initiation and clinical outcomes in human immunodeficiency virus type 1 seroconverters.

Journal Article Arch Intern Med · September 26, 2011 BACKGROUND: To estimate the clinical benefit of highly active antiretroviral therapy (HAART) initiation vs deferral in a given month in patients with CD4 cell counts less than 800/μL. METHODS: In this observational cohort study of human immunodeficiency vi ... Full text Link to item Cite

Improved doubly robust estimation when data are monotonely coarsened, with application to longitudinal studies with dropout.

Journal Article Biometrics · June 2011 A routine challenge is that of making inference on parameters in a statistical model of interest from longitudinal data subject to dropout, which are a special case of the more general setting of monotonely coarsened data. Considerable recent attention has ... Full text Link to item Cite

Inference on treatment effects from a randomized clinical trial in the presence of premature treatment discontinuation: the SYNERGY trial.

Journal Article Biostatistics · April 2011 The Superior Yield of the New Strategy of Enoxaparin, Revascularization, and GlYcoprotein IIb/IIIa inhibitors (SYNERGY) was a randomized, open-label, multicenter clinical trial comparing 2 anticoagulant drugs on the basis of time-to-event endpoints. In con ... Full text Link to item Cite

Doubly robust estimation of causal effects.

Journal Article Am J Epidemiol · April 1, 2011 Doubly robust estimation combines a form of outcome regression with a model for the exposure (i.e., the propensity score) to estimate the causal effect of an exposure on an outcome. When used individually to estimate a causal effect, both outcome regressio ... Full text Link to item Cite

Report of the Editors-2010

Journal Article Biometrics · January 1, 2011 Full text Cite

Experimental statistics for biological sciences.

Journal Article Methods Mol Biol · 2010 In this chapter, we cover basic and fundamental principles and methods in statistics - from "What are Data and Statistics?" to "ANOVA and linear regression," which are the basis of any statistical thinking and undertaking. Readers can easily find the selec ... Full text Link to item Cite

Demographic and historical findings, including exposure to environmental tobacco smoke, in dogs with chronic cough.

Journal Article J Vet Intern Med · 2010 BACKGROUND: Controlled studies investigating risk factors for the common presenting problem of chronic cough in dogs are lacking. HYPOTHESIS/OBJECTIVES: To identify demographic and historical factors associated with chronic cough in dogs, and associations ... Full text Link to item Cite

EFFECT OF HAART INITIATION ON CLINICAL OUTCOMES IN HIV-1 INFECTED PATIENTS

Conference AMERICAN JOURNAL OF EPIDEMIOLOGY · 2010 Cite

Report of the editors - 2009

Journal Article Biometrics · January 1, 2010 Full text Cite

An inverse problem statistical methodology summary

Chapter · December 1, 2009 We discuss statistical and computational aspects of inverse or parameter estimation problems for deterministic dynamical systems based on Ordinary Least Squares and Generalized Least Squares with appropriate corresponding data noise assumptions of constant ... Full text Cite

Non-linear Models for Longitudinal Data.

Journal Article Am Stat · November 1, 2009 While marginal models, random-effects models, and conditional models are routinely considered to be the three main modeling families for continuous and discrete repeated measures with linear and generalized linear mean structures, respectively, it is less ... Full text Link to item Cite

Improving efficiency and robustness of the doubly robust estimator for a population mean with incomplete data.

Journal Article Biometrika · September 2009 Considerable recent interest has focused on doubly robust estimators for a population mean response in the presence of incomplete data, which involve models for both the propensity score and the regression of outcome on covariates. The usual doubly robust ... Full text Link to item Cite

Latent-model robustness in joint models for a primary endpoint and a longitudinal process.

Journal Article Biometrics · September 2009 Joint modeling of a primary response and a longitudinal process via shared random effects is widely used in many areas of application. Likelihood-based inference on joint models requires model specification of the random effects. Inappropriate model specif ... Full text Link to item Cite

Gene-trait similarity regression for multimarker-based association analysis.

Journal Article Biometrics · September 2009 We propose a similarity-based regression method to detect associations between traits and multimarker genotypes. The model regresses similarity in traits for pairs of "unrelated" individuals on their haplotype similarities, and detects the significance by ... Full text Link to item Cite

A Model for HCMV Infection in Immunosuppressed Patients.

Journal Article Math Comput Model · April 2009 We propose a model for HCMV infection in healthy and immunosuppressed patients. First, we present the biological model and formulate a system of ordinary differential equations to describe the pathogenesis of primary HCMV infection in immunocompetent and i ... Full text Link to item Cite

Report of the Editors - 2008

Journal Article Biometrics · January 1, 2009 Full text Cite

'Smooth' inference for survival functions with arbitrarily censored data.

Journal Article Stat Med · November 20, 2008 We propose a procedure for estimating the survival function of a time-to-event random variable under arbitrary patterns of censoring. The method is predicated on the mild assumption that the distribution of the random variable, and hence the survival funct ... Full text Link to item Cite

Covariate adjustment for two-sample treatment comparisons in randomized clinical trials: a principled yet flexible approach.

Journal Article Stat Med · October 15, 2008 There is considerable debate regarding whether and how covariate-adjusted analyses should be used in the comparison of treatments in randomized clinical trials. Substantial baseline covariate information is routinely collected in such trials, and one goal ... Full text Link to item Cite

Modelling HIV immune response and validation with clinical data.

Journal Article J Biol Dyn · October 2008 A system of ordinary differential equations is formulated to describe the pathogenesis of HIV infection, wherein certain features that have been shown to be important by recent experimental research are incorporated in the model. These include the role of ... Full text Link to item Cite

Improving efficiency of inferences in randomized clinical trials using auxiliary covariates.

Journal Article Biometrics · September 2008 The primary goal of a randomized clinical trial is to make comparisons among two or more treatments. For example, in a two-arm trial with continuous response, the focus may be on the difference in treatment means; with more than two treatments, the compari ... Full text Link to item Cite

Non-linear mixed-effects models

Chapter · August 11, 2008 Full text Cite

"Smooth" semiparametric regression analysis for arbitrarily censored time-to-event data.

Journal Article Biometrics · June 2008 A general framework for regression analysis of time-to-event data subject to arbitrary patterns of censoring is proposed. The approach is relevant when the analyst is willing to assume that distributions governing model components that are ordinarily left ... Full text Link to item Cite

Report of the editors - 2007

Journal Article Biometrics · January 1, 2008 Full text Cite

Likelihood and Pseudo-likelihood Methods for Semiparametric Joint Models for a Primary Endpoint and Longitudinal Data.

Journal Article Comput Stat Data Anal · August 15, 2007 Inference on the association between a primary endpoint and features of longitudinal profiles of a continuous response is of central interest in medical and public health research. Joint models that represent the association through shared dependence of th ... Full text Link to item Cite

Using mathematical modeling and control to develop structured treatment interruption strategies for HIV infection.

Journal Article Drug Alcohol Depend · May 2007 The goal of this article is to suggest that mathematical models describing biological processes taking place within a patient over time can be used to design adaptive treatment strategies. We demonstrate using the key example of treatment strategies for hu ... Full text Link to item Cite

Estimation and prediction with HIV-treatment interruption data.

Journal Article Bull Math Biol · February 2007 We consider longitudinal clinical data for HIV patients undergoing treatment interruptions. We use a nonlinear dynamical mathematical model in attempts to fit individual patient data. A statistically-based censored data method is combined with inverse prob ... Full text Link to item Cite

Smoothing spline-based score tests for proportional hazards models.

Journal Article Biometrics · September 2006 We propose "score-type" tests for the proportional hazards assumption and for covariate effects in the Cox model using the natural smoothing spline representation of the corresponding nonparametric functions of time or covariate. The tests are based on the ... Full text Link to item Cite

HIV dynamics: Modeling, data analysis, and optimal treatment protocols

Journal Article Journal of Computational and Applied Mathematics · December 2005 Full text Cite

Semiparametric Estimation of Treatment Effect in a Pretest-Posttest Study with Missing Data.

Journal Article Stat Sci · August 2005 The pretest-posttest study is commonplace in numerous applications. Typically, subjects are randomized to two treatments, and response is measured at baseline, prior to intervention with the randomized treatment (pretest), and at prespecified follow-up tim ... Full text Link to item Cite

Surgeons' economic profiles: can we get the "right" answers?

Journal Article J Med Syst · April 2005 Hospitals and payers use economic profiling to evaluate physician and surgeon performance. However, there is significant variation in the data sources and analytic methods that are used. We used information from a hospital's cardiac surgery and cost accoun ... Full text Link to item Cite

iometrics

Other · February 15, 2005 AbstractBiometrics is a quarterly journal of the International Biometric Society (IBS), which is a highly regarded outlet for reports on statistical and mathema ... Full text Cite

Stratification and weighting via the propensity score in estimation of causal treatment effects: a comparative study.

Journal Article Stat Med · October 15, 2004 Estimation of treatment effects with causal interpretation from observational data is complicated because exposure to treatment may be confounded with subject characteristics. The propensity score, the probability of treatment exposure conditional on covar ... Full text Link to item Cite

Likelihood and conditional likelihood inference for generalized additive mixed models for clustered data

Journal Article Journal of Multivariate Analysis · October 1, 2004 Lin and Zhang (J. Roy. Statist. Soc. Ser. B 61 (1999) 381) proposed the generalized additive mixed model (GAMM) as a framework for analysis of correlated data, where normally distributed random effects are used to account for correlation in the data, and p ... Full text Cite

Joint modeling of longitudinal and time-to-event data: An overview

Conference Statistica Sinica · July 1, 2004 A common objective in longitudinal studies is to characterize the relationship between a longitudinal response process and a time-to-event. Considerable recent interest has focused on so-called joint models, where models for the event time distribution and ... Cite

Discussion of two important missing data issues

Conference Statistica Sinica · July 1, 2004 Cite

Discussion of joint modeling longitudinal and survival data

Conference Statistica Sinica · July 1, 2004 Cite

Marginal structural models for analyzing causal effects of time-dependent treatments: an application in perinatal epidemiology.

Journal Article Am J Epidemiol · May 15, 2004 Marginal structural models (MSMs) are causal models designed to adjust for time-dependent confounding in observational studies of time-varying treatments. MSMs are powerful tools for assessing causality with complicated, longitudinal data sets but have not ... Full text Link to item Cite

Conditional estimation for generalized linear models when covariates are subject-specific parameters in a mixed model for longitudinal measurements.

Journal Article Biometrics · March 2004 The relationship between a primary endpoint and features of longitudinal profiles of a continuous response is often of interest, and a relevant framework is that of a generalized linear model with covariates that are subject-specific random effects in a li ... Full text Link to item Cite

Differential treatment benefit of platelet glycoprotein IIb/IIIa inhibition with percutaneous coronary intervention versus medical therapy for acute coronary syndromes: exploration of methods.

Journal Article Circulation · February 10, 2004 BACKGROUND: Although many believe that platelet glycoprotein IIb/IIIa inhibitors should be used only in acute coronary syndrome patients undergoing percutaneous coronary intervention, supporting data from randomized clinical trials are tenuous. The assumpt ... Full text Link to item Cite

Nonlinear models for repeated measurement data: An overview and update

Journal Article Journal of Agricultural, Biological, and Environmental Statistics · December 2003 Full text Cite

Robust two-stage approach to repeated measurements analysis of chronic ozone exposure in rats

Journal Article Journal of Agricultural, Biological, and Environmental Statistics · December 2003 Full text Cite

Semiparametric estimation of treatment effect in a pretest-posttest study.

Journal Article Biometrics · December 2003 Inference on treatment effects in a pretest-posttest study is a routine objective in medicine, public health, and other fields. A number of approaches have been advocated. We take a semiparametric perspective, making no assumptions about the distributions ... Full text Link to item Cite

An estimator for the proportional hazards model with multiple longitudinal covariates measured with error.

Journal Article Biostatistics · December 2002 In many longitudinal studies, it is of interest to characterize the relationship between a time-to-event (e.g. survival) and several time-dependent and time-independent covariates. Time-dependent covariates are generally observed intermittently and with er ... Full text Link to item Cite

A semiparametric likelihood approach to joint modeling of longitudinal and time-to-event data.

Journal Article Biometrics · December 2002 Joint models for a time-to-event (e.g., survival) and a longitudinal response have generated considerable recent interest. The longitudinal data are assumed to follow a mixed effects model, and a proportional hazards model depending on the longitudinal ran ... Full text Link to item Cite

Randomized COMparison of platelet inhibition with abciximab, tiRofiban and eptifibatide during percutaneous coronary intervention in acute coronary syndromes: the COMPARE trial. Comparison Of Measurements of Platelet aggregation with Aggrastat, Reopro, and Eptifibatide.

Journal Article Circulation · September 17, 2002 BACKGROUND: The relative anti-aggregatory effects of currently prescribed platelet glycoprotein IIb/IIIa receptor antagonists during and after percutaneous coronary intervention for acute coronary syndromes have not been established. METHODS AND RESULTS: W ... Full text Link to item Cite

A Monte Carlo EM algorithm for generalized linear mixed models with flexible random effects distribution.

Journal Article Biostatistics · September 2002 A popular way to represent clustered binary, count, or other data is via the generalized linear mixed model framework, which accommodates correlation through incorporation of random effects. A standard assumption is that the random effects follow a paramet ... Full text Link to item Cite

Estimation of survival distributions of treatment policies in two-stage randomization designs in clinical trials.

Journal Article Biometrics · March 2002 Some clinical trials follow a design where patients are randomized to a primary therapy at entry followed by another randomization to maintenance therapy contingent upon disease remission. Ideally, analysis would allow different treatment policies, i.e., c ... Full text Link to item Cite

Constrained four parameter logistic model.

Journal Article Dev Biol (Basel) · 2002 The constrained four parameter logistic model has found wide application in describing dose response relationships across many assay systems. This discussion examines the basic model and its practical application to potency testing in the context of the 96 ... Link to item Cite

Linear mixed models with flexible distributions of random effects for longitudinal data.

Journal Article Biometrics · September 2001 Normality of random effects is a routine assumption for the linear mixed model, but it may be unrealistic, obscuring important features of among-individual variation. We relax this assumption by approximating the random effects density by the seminonparame ... Full text Link to item Cite

Robust two-stage estimation in hierarchical nonlinear models.

Journal Article Biometrics · March 2001 Hierarchical models encompass two sources of variation, namely within and among individuals in the population; thus, it is important to identify outliers that may arise at each sampling level. A two-stage approach to analyzing nonlinear repeated measuremen ... Full text Link to item Cite

Differences in viral dynamics between genotypes 1 and 2 of hepatitis C virus.

Journal Article J Infect Dis · July 2000 Many studies have shown that patients infected with hepatitis C virus (HCV) of genotype 2 have better response to interferon (IFN)-alpha treatment than genotype 1 patients; however, the mechanisms responsible for this difference are not understood. In this ... Full text Link to item Cite

Correcting for measurement error in individual-level covariates in nonlinear mixed effects models.

Journal Article Biometrics · June 2000 The nonlinear mixed effects model is used to represent data in pharmacokinetics, viral dynamics, and other areas where an objective is to elucidate associations among individual-specific model parameters and covariates; however, covariates may be measured ... Full text Link to item Cite

Estimating data transformations in nonlinear mixed effects models.

Journal Article Biometrics · March 2000 A routine practice in the analysis of repeated measurement data is to represent individual responses by a mixed effects model on some transformed scale. For example, for pharmacokinetic, growth, and other data, both the response and the regression model ar ... Full text Link to item Cite

Consequences of misspecifying assumptions in nonlinear mixed effects models

Journal Article Computational Statistics and Data Analysis · January 1, 2000 The nonlinear mixed effects model provides a framework for inference in a number of applications, most notably pharmacokinetics and pharmacodynamics, but also in HIV and other disease dynamics and in a host of other longitudinal-data settings. In these mod ... Full text Cite

Human immunodeficiency virus type 1-specific cytotoxic T lymphocyte activity is inversely correlated with HIV type 1 viral load in HIV type 1-infected long-term survivors.

Journal Article AIDS Res Hum Retroviruses · September 1, 1999 HIV-1-specific cytotoxic T cell (CTL) activity has been suggested to correlate with protection from progression to AIDS. We have examined the relationship between HIV-specific CTL activity and maintenance of peripheral blood CD4+ T lymphocyte counts and co ... Full text Link to item Cite

Laser scanning cytometry quantification of estrogen receptors in breast cancer.

Journal Article Anal Quant Cytol Histol · December 1998 OBJECTIVE: To describe the laser scanning cytometry (LSC) processing and analysis developed for the quantitative analysis of estrogen receptor (ER) content in routine paraffin sections of breast carcinomas. STUDY DESIGN: Histologic sections of archival, pa ... Link to item Cite

Estimating the parameters in the Cox model when covariate variables are measured with error.

Journal Article Biometrics · December 1998 The Cox proportional hazards model is commonly used to model survival data as a function of covariates. Because of the measuring mechanism or the nature of the environment, covariates are often measured with error and are not directly observable. A naive a ... Link to item Cite

The effect of serial dilution error on calibration inference in immunoassay.

Journal Article Biometrics · March 1998 A common practice in immunoassay is the use of sequential dilutions of an initial stock solution of the antigen of interest to obtain standard samples in a desired concentration range. Nonlinear, heteroscedastic regression models are a common framework for ... Link to item Cite

Calibration inference based on multiple runs of an immunoassay.

Journal Article Biometrics · December 1997 Several authors have documented the poor performance of usual large-sample, individual calibration confidence intervals based on a single run of an immunoassay. Inaccuracy of these intervals may be attributed to the paucity of information on model paramete ... Link to item Cite

Testing homogeneity of intra-run variance parameters in immunoassay.

Journal Article Stat Med · August 15, 1997 A common assumption in the analysis of immunoassay data is a similar pattern of within-run variation across runs of the assays. One makes this assumption without formal investigation of its validity, despite the widely acknowledged fact that accurate under ... Full text Link to item Cite

Bootstrap-Adjusted Calibration Confidence Intervals for Immunoassay

Journal Article Journal of the American Statistical Association · March 1997 Full text Cite

Bootstrap-Adjusted Calibration Confidence Intervals for Immunoassay

Journal Article Journal of the American Statistical Association · March 1997 Full text Cite

Organic Matter Decomposition following Harvesting and Site Preparation of a Forested Wetland

Journal Article Soil Science Society of America Journal · November 1996 AbstractOrganic matter accumulation is an important process that affects ecosystem function in many northern wetlands. The cotton strip assay (CSA) was used to measure the effect of harvesting and two different site prepara ... Full text Cite

Adenocarcinoma of the retinal pigment epithelium: a diagnostic and therapeutic challenge.

Journal Article Graefes Arch Clin Exp Ophthalmol · August 1996 BACKGROUND: Adenocarcinoma of the retinal pigment epithelium (RPE) is an uncommon intraocular tumor which has been rarely if ever diagnosed prior to enucleation. Our review of the literature suggests that when a melanotic and tuberous-shaped tumor presents ... Full text Link to item Cite

Pyrimethamine pharmacokinetics in human immunodeficiency virus-positive patients seropositive for Toxoplasma gondii.

Journal Article Antimicrob Agents Chemother · June 1996 Pyrimethamine pharmacokinetics were studied in 11 human immunodeficiency virus (HIV)-positive patients who were seropositive for exposure to Toxoplasma gondii and were taking zidovudine (AIDS Clinical Trials Group Protocol 102). Pyrimethamine was administe ... Full text Link to item Cite

The effect of variance function estimation on nonlinear calibration inference in immunoassay data.

Journal Article Biometrics · March 1996 Often with data from immunoassays, the concentration-response relationship is nonlinear and intra-assay response variance is heterogeneous. Estimation of the standard curve is usually based on a nonlinear heteroscedastic regression model for concentration- ... Link to item Cite

Denaturation and Aggregation of Chicken Myosin Isoforms

Journal Article Journal of Agricultural and Food Chemistry · January 1, 1996 Full text Cite

Therapeutic effects of diethylcarbamazine and 3'-azido-3'-deoxythymidine on feline leukemia virus lymphoma formation.

Journal Article Vet Immunol Immunopathol · May 1995 Twenty-four specific pathogen-free kittens were infected with the Rickard strain of feline leukemia virus (FeLVR). The kittens were divided into four equal groups and were orally administered either a high dose of diethylcarbamazine (DECH, 12 mg kg-1), a l ... Full text Link to item Cite

Assays for recombinant proteins: a problem in non-linear calibration.

Journal Article Stat Med · June 15, 1994 Quantification of protein levels in biological matrices such as serum or plasma frequently relies on the techniques of immunoassay or bioassay. The relevant statistical problem is that of non-linear calibration, where one estimates analyte concentration in ... Full text Link to item Cite

Population pharmacokinetic/pharmacodynamic methodology and applications: a bibliography.

Journal Article Biometrics · June 1994 This bibliography lists all published methodological works (statistical methodology, implementation methodology, review papers, descriptions of software) in the area of population pharmacokinetics/pharmacodynamics up to 1993 and all published works describ ... Link to item Cite

The nonlinear mixed effects model with a smooth random effects density

Journal Article Biometrika · September 1, 1993 SUMMARY: The fixed parameters of the nonlinear mixed effects model and the density of the random effects are estimated jointly by maximum likelihood. The density of the random effects is assumed to be smooth but is otherwise unrestricted. The method uses a ... Full text Cite

Analysis of repeated measurement data using the nonlinear mixed effects model

Journal Article Chemometrics and Intelligent Laboratory Systems · August 1993 Full text Cite

Morphological and physiological changes in the urinary tract associated with ureteral dilation and ureteropyeloscopy: an experimental study.

Journal Article J Urol · June 1993 The gross and microscopic effects of four common modes of ureteral dilation and ureteroscopy were examined in 26 renoureteral units in 13 minipigs. Acutely, ureters subjected to mechanical (bougie, Teflon, or balloon) ureteral dilation and ureteropyeloscop ... Full text Link to item Cite

Some general estimation methods for nonlinear mixed-effects models.

Journal Article J Biopharm Stat · March 1993 A nonlinear mixed-effects model suitable for characterizing repeated measurement data is described. The model allows dependence of random coefficients on covariate information and accommodates general specifications of a common intraindividual covariance s ... Full text Link to item Cite

Smooth nonparametric maximum likelihood estimation for population pharmacokinetics, with application to quinidine.

Journal Article J Pharmacokinet Biopharm · October 1992 The seminonparametric (SNP) method, popular in the econometrics literature, is proposed for use in population pharmacokinetic analysis. For data that can be described by the nonlinear mixed effects model, the method produces smooth nonparametric estimates ... Full text Link to item Cite

THE USE OF REGRESSION-ANALYSIS IN NONWOVENS RESEARCH

Conference 1991 NONWOVENS CONFERENCE · 1991 Cite

Regression and calibration with nonconstant error variance

Journal Article Chemometrics and Intelligent Laboratory Systems · December 1990 Full text Cite

Gastrointestinal milk intolerance of infancy.

Journal Article Am J Dis Child · March 1989 During a period of 30 months, cow's milk- or soy protein-induced colitis was diagnosed in 22 infants. All patients presented with hematochezia. Only three patients had substantial diarrhea. Colonoscopic evaluations demonstrated a characteristic mucosal app ... Full text Link to item Cite

Electrocardiographic pseudo-myocardial infarct pattern in malignant cardiac disease.

Journal Article Cancer · March 1, 1989 A patient with disseminated diffuse histiocytic lymphoma had persistent electrocardiographic (ECG) signs of acute myocardial infarction without clinical, enzymatic, or hemodynamic evidence of myocardial necrosis. The ECG findings were felt to be secondary ... Full text Link to item Cite

Reduced cardiac selenium content in the acquired immunodeficiency syndrome.

Journal Article JPEN J Parenter Enteral Nutr · 1989 Selenium deficiency has been implicated in the pathogenesis of a dilated congestive cardiomyopathy in areas of China (Keshan disease) and in several patients on long-term total parenteral nutrition. Recently a clinically and pathologically similar cardiomy ... Full text Link to item Cite

Progesterone receptors in the human heart and great vessels.

Journal Article Lab Invest · September 1988 Progesterone receptors (PgR) were identified in 31 of 50 specimens of human (men and women) thoracic ascending aorta, internal carotid, coronary artery, and left atrial appendage. This was accomplished with a peroxidase-antiperoxidase immunocytochemical as ... Link to item Cite

A Note on Extended Quasi-Likelihood

Journal Article Journal of the Royal Statistical Society Series B: Statistical Methodology · September 1, 1988 SUMMARYWe study the method of extended quasi-likelihood estimation and inference of a variance function recently proposed by Nelder and Pregibon. The estimates are inconsistent in general, and the test level ... Full text Cite

Intestinal duplication in a patient with neurofibromatosis: aid of ultrasound and CT scan in diagnosis.

Journal Article J Pediatr Gastroenterol Nutr · 1988 A 5-year-old boy with neurofibromatosis is described, whose symptoms of abdominal pain and vomiting were due to an intestinal duplication. Intestinal duplication has not been previously reported as a cause of gastrointestinal symptoms in neurofibromatosis. ... Full text Link to item Cite

Variance Function Estimation

Journal Article Journal of the American Statistical Association · December 1987 Full text Cite

Life-threatening dysrhythmias in varicella myocarditis.

Journal Article Clin Pediatr (Phila) · September 1987 Varicella myocarditis is an unusual complication of a common childhood disease. Two patients with life-threatening dysrhythmias and circulatory failure are reported. One patient required permanent pacemaker implantation for acquired complete heart block, n ... Full text Link to item Cite

Optimal Dynamic Treatment Regimes

Other AbstractA dynamic treatment regime is a set of sequential decision rules, each corresponding to a key decision point in a disease or disorder process that dictates the next treatment for a patient based on accrue ... Full text Cite

‐Learning

Other AbstractQ‐learning is a regression‐based approximate dynamic programming algorithm that is commonly used to estimate sequences of decision rules that maximizes mean utility when applied to the population of interest. Becaus ... Full text Cite