abstract：:Multivariate finite mixture models have been applied to the identification of dietary patterns. These models are known to have many parameters, and consequently large samples are usually required. We present a special case of a multivariate mixture model that reduces the number of parameters to be estimated and seems ...

journal_title：Statistics in medicine

authors： Rita Gaio A,Costa JP,Santos AC,Ramos E,Lopes C

更新日期：2012-08-30 00:00:00

abstract：:There is a single-minded focus on events in survival analysis, and we often ignore longitudinal data that are collected together with the event data. This is due to a lack of methodology but also a result of the artificial distinction between survival and longitudinal data analyses. Understanding the dynamics of such ...

journal_title：Statistics in medicine

authors： Aalen OO

更新日期：2012-08-15 00:00:00

abstract：:Biomarkers, increasingly used in biomedical studies for the diagnosis and prognosis of acute and chronic diseases, provide insight into the effectiveness of treatments and potential pathways that can be used to guide future treatment targets. The measurement of these markers is often limited by the sensitivity of the ...

journal_title：Statistics in medicine

authors： Lee M,Kong L,Weissfeld L

更新日期：2012-07-30 00:00:00

abstract：:Meta-analyses pooling continuous outcomes can use mean differences (MD), standardized MD (MD in pooled standard deviation units, SMD), or ratio of arithmetic means (RoM). Recently, ratio of geometric means using ad hoc (RoGM (ad hoc) ) or Taylor series (RoGM (Taylor) ) methods for estimating variances have been propos...

journal_title：Statistics in medicine

authors： Friedrich JO,Adhikari NK,Beyene J

更新日期：2012-07-30 00:00:00

abstract：:There is growing interest in how best to adapt and readapt treatments to individuals to maximize clinical benefit. In response, adaptive treatment strategies (ATS), which operationalize adaptive, sequential clinical decision making, have been developed. From a patient's perspective an ATS is a sequence of treatments, ...

journal_title：Statistics in medicine

authors： Almirall D,Compton SN,Gunlicks-Stoessel M,Duan N,Murphy SA

更新日期：2012-07-30 00:00:00

abstract：:Missing data arise in crossover trials, as they do in any form of clinical trial. Several papers have addressed the problems that missing data create, although almost all of these assume that the probability that a planned observation is missing does not depend on the value that would have been observed; that is, the ...

journal_title：Statistics in medicine

authors： Ho WK,Matthews JN,Henderson R,Farewell D,Rodgers LR

更新日期：2012-07-20 00:00:00

abstract：:We present an approach for inference on contrasts of clinically meaningful functionals of a survivor distribution (e.g., restricted mean, quantiles) that can avoid strong parametric or semiparametric assumptions on the underlying structure of the data. In this multistage approach, we first use an adaptive predictive m...

journal_title：Statistics in medicine

authors： Rudser KD,LeBlanc ML,Emerson SS

更新日期：2012-07-20 00:00:00

abstract：:Tree-based methods have become popular for analyzing complex data structures where the primary goal is risk stratification of patients. Ensemble techniques improve the accuracy in prediction and address the instability in a single tree by growing an ensemble of trees and aggregating. However, in the process, individua...

journal_title：Statistics in medicine

authors： Banerjee M,Ding Y,Noone AM

更新日期：2012-07-10 00:00:00

abstract：:Hospital length of stay (LOS) is an important measure of healthcare utilization and is generally positively skewed and heterogeneous. We fit a Coxian phase-type distribution to LOS and identify the hidden states of the underlying latent homogeneous Markov model. We demonstrate that selecting an appropriate number of p...

journal_title：Statistics in medicine

authors： Tang X,Luo Z,Gardiner JC

更新日期：2012-06-30 00:00:00

abstract：:Bioequivalence or interaction trials are commonly studied in crossover design and can be analysed by nonlinear mixed effects models as an alternative to noncompartmental approach. We propose an extension of the population Fisher information matrix in nonlinear mixed effects models to design crossover pharmacokinetic t...

journal_title：Statistics in medicine

authors： Nguyen TT,Bazzoli C,Mentré F

更新日期：2012-05-20 00:00:00

abstract：:Quality of life (QOL) assessment is a key component of many clinical studies and frequently requires the use of single global summary measures that capture the overall balance of findings from a potentially wide-ranging assessment of QOL issues. We propose and evaluate an irregular multilevel latent variable model sui...

journal_title：Statistics in medicine

authors： Kifley A,Heller GZ,Beath KJ,Bulger D,Ma J,Gebski V

更新日期：2012-05-20 00:00:00

abstract：:For genome-wide association studies, we propose a new method for identifying significant biological pathways. In this approach, we aggregate data across single-nucleotide polymorphisms to obtain summary measures at the gene level. We then use a hierarchical Bayesian model, which takes the gene-level summary measures a...

journal_title：Statistics in medicine

authors： Shahbaba B,Shachaf CM,Yu Z

更新日期：2012-05-10 00:00:00

abstract：:A problem occurring in chronic disease modeling is the estimation of transition probabilities of moving from one state of a categorical risk factor to another. Transitions could be obtained from a cohort study, but often such data may not be available. However, under the assumption that transitions remain stable over ...

journal_title：Statistics in medicine

authors： Kassteele Jv,Hoogenveen RT,Engelfriet PM,Baal PH,Boshuizen HC

更新日期：2012-03-15 00:00:00

abstract：:Childhood acute lymphoblastic leukaemia is treated with long-term intensive chemotherapy. During the latter part of the treatment, the maintenance therapy, the patients receive oral doses of two cytostatics. The doses are tailored to blood counts measured on a weekly basis, and the treatment is therefore highly dynami...

journal_title：Statistics in medicine

authors： Rosthøj S,Keiding N,Schmiegelow K

更新日期：2012-02-28 00:00:00

abstract：:Virtually all clinical trials collect multiple endpoints that are usually correlated. Many methods have been proposed to control the family-wise type I error rate (FWER), but these methods often disregard the correlation among the endpoints, such as the commonly used Bonferroni correction, Holm procedure, Wiens' Bonfe...

journal_title：Statistics in medicine

authors： Xie C

更新日期：2012-02-20 00:00:00

abstract：:A frequent objective in medical research is the investigation of differences in patient survival between several experimental treatments and one standard treatment. In order to assess these differences statistically, we have to apply adjustments for multiple comparisons to prevent an increased number of false-positive...

journal_title：Statistics in medicine

authors： Herberich E,Hothorn T

更新日期：2012-01-13 00:00:00

abstract：:Within the rich literature on generalized linear models, substantial efforts have been devoted to models for categorical responses that are either completely ordered or completely unordered. Few studies have focused on the analysis of partially ordered outcomes, which arise in practically every area of study, includin...

journal_title：Statistics in medicine

authors： Zhang Q,Ip EH

更新日期：2012-01-13 00:00:00

abstract：:This paper discusses the benefits and limitations of adaptive sample size re-estimation for phase 3 confirmatory clinical trials. Comparisons are made with more traditional fixed sample and group sequential designs. It is seen that the real benefit of the adaptive approach arises through the ability to invest sample s...

journal_title：Statistics in medicine

authors： Mehta CR,Pocock SJ

更新日期：2011-12-10 00:00:00

abstract：:In this paper, we define a modified version τ(b) of Kendall's tau to measure the association in a pair (X,Y) of random variables subject to fixed left censoring due to known lower detection limits. We provide a nonparametric estimator of τ(b) and investigate its asymptotic properties. We then assume an Archimedean cop...

journal_title：Statistics in medicine

authors： Romdhani H,Lakhal-Chaieb L

更新日期：2011-11-20 00:00:00

abstract：:Recurrent event data occur in many clinical and observational studies, and in these situations, there may exist a terminal event such as death that is related to the recurrent event of interest. In addition, sometimes more than one type of recurrent events may occur, that is, one may encounter multivariate recurrent e...

journal_title：Statistics in medicine

authors： Zhu L,Sun J,Srivastava DK,Tong X,Leisenring W,Zhang H,Robison LL

更新日期：2011-11-10 00:00:00

abstract：:Meta-analysis is the methodology for combining findings from similar research studies asking the same question. When the question of interest involves multiple outcomes, multivariate meta-analysis is used to synthesize the outcomes simultaneously taking into account the correlation between the outcomes. Likelihood-bas...

journal_title：Statistics in medicine

authors： Ma Y,Mazumdar M

更新日期：2011-10-30 00:00:00

abstract：:We consider the problem of identifying a subgroup of patients who may have an enhanced treatment effect in a randomized clinical trial, and it is desirable that the subgroup be defined by a limited number of covariates. For this problem, the development of a standard, pre-determined strategy may help to avoid the well...

journal_title：Statistics in medicine

authors： Foster JC,Taylor JM,Ruberg SJ

更新日期：2011-10-30 00:00:00

abstract：:We extend the shared frailty model of recurrent events and a dependent terminal event to allow for a nonparametric covariate function. We include a Gaussian random effect (frailty) in the intensity functions of both the recurrent and terminal events to capture correlation between the two processes. We employ the penal...

journal_title：Statistics in medicine

authors： Zhangsheng Y,Liu L

更新日期：2011-09-30 00:00:00

abstract：:This paper introduces a dynamic clustering methodology based on multi-valued descriptors of dermoscopic images. The main idea is to support medical diagnosis to decide if pigmented skin lesions belonging to an uncertain set are nearer to malignant melanoma or to benign nevi. Melanoma is the most deadly skin cancer, an...

journal_title：Statistics in medicine

authors： Cozza V,Guarracino MR,Maddalena L,Baroni A

更新日期：2011-09-10 00:00:00

abstract：:The goal of phase I cancer trials is to determine the highest dose of a treatment regimen with an acceptable toxicity rate. Traditional designs for phase I trials, such as the Continual Reassessment Method (CRM) and the 3 + 3 design, require each patient or a cohort of patients to be fully evaluated for the dose-limit...

journal_title：Statistics in medicine

authors： Polley MY

更新日期：2011-07-30 00:00:00

abstract：:An important problem in oncology is comparing chemotherapy (chemo) agents in terms of their effects on survival or progression-free survival time. When the goal is to evaluate individual agents, a difficulty commonly encountered with observational data is that many patients receive a chemo combination including two or...

journal_title：Statistics in medicine

authors： Thall PF,Liu DD,Berrak SG,Wolff JE

更新日期：2011-07-10 00:00:00

abstract：:In many biomedical and epidemiological studies, data are often clustered due to longitudinal follow up or repeated sampling. While in some clustered data the cluster size is pre-determined, in others it may be correlated with the outcome of subunits, resulting in informative cluster size. When the cluster size is info...

journal_title：Statistics in medicine

authors： Chen Z,Zhang B,Albert PS

更新日期：2011-07-10 00:00:00

abstract：:Public health interventions are often designed to target communities defined either geographically (e.g. cities, counties) or socially (e.g. schools or workplaces). The group randomized trial (GRT) is regarded as the gold standard for evaluating these interventions. However, community leaders may object to randomizati...

journal_title：Statistics in medicine

authors： Pennell ML,Hade EM,Murray DM,Rhoda DA

更新日期：2011-07-10 00:00:00

abstract：:Algorithms for identifying public health threats or disease outbreaks are vulnerable to false alarms arising from sudden shifts in health-care utilization or data participation. This paper describes a method of reducing false alerts in automated public health surveillance algorithms, and in particular, automated syndr...

journal_title：Statistics in medicine

authors： Peter W,Najmi AH,Burkom HS

更新日期：2011-06-30 00:00:00

abstract：:It is well established that neural activity is stochastically modulated over time. Therefore, direct comparisons across experimental conditions and determination of change points or maximum firing rates are not straightforward. This study sought to compare temporal firing probability curves that may vary across groups...

journal_title：Statistics in medicine

authors： Roca-Pardiñas J,Cadarso-Suárez C,Pardo-Vazquez JL,Leboran V,Molenberghs G,Faes C,Acuña C

更新日期：2011-06-30 00:00:00

abstract：:Linear mixed effects (LME) models are increasingly used for analyses of biological and biomedical data. When the multivariate normal assumption is not adequate for an LME model, then a robust estimation approach is preferable to the maximum likelihood one. M-estimators were considered before for robust estimation of t...

journal_title：Statistics in medicine

authors： Chervoneva I,Vishnyakov M

更新日期：2011-06-30 00:00:00

abstract：BACKGROUND:The need to deliver interventions targeting multiple diseases in a cost-effective manner calls for integrated disease control efforts. Consequently, maps are required that show where the risk of co-infection is particularly high. Co-infection risk is preferably estimated via Bayesian geostatistical multinomi...

journal_title：Statistics in medicine

authors： Schur N,Gosoniu L,Raso G,Utzinger J,Vounatsou P

更新日期：2011-06-30 00:00:00

abstract：:The usual methods for analyzing case-cohort studies rely on sometimes not fully efficient weighted estimators. Multiple imputation might be a good alternative because it uses all the data available and approximates the maximum partial likelihood estimator. This method is based on the generation of several plausible co...

journal_title：Statistics in medicine

authors： Marti H,Chavance M

更新日期：2011-06-15 00:00:00

abstract：:Adaptive designs or flexible designs in a broader sense have increasingly been considered in planning pivotal registration clinical trials. Sample size reassessment design and adaptive selection design are two of such designs that appear in regulatory applications. At the design stage, consideration of sample size rea...

journal_title：Statistics in medicine

authors： Hung HM,Wang SJ,O'Neill R

更新日期：2011-06-15 00:00:00

abstract：:Sequential analysis is frequently employed to address ethical and financial issues in clinical trials. Sequential analysis may be performed using standard group sequential designs, or, more recently, with adaptive designs that use estimates of treatment effect to modify the maximal statistical information to be collec...

journal_title：Statistics in medicine

authors： Emerson SC,Rudser KD,Emerson SS

更新日期：2011-05-20 00:00:00

abstract：:In designed longitudinal studies, information from the same set of subjects are collected repeatedly over time. The longitudinal measurements are often subject to missing data which impose an analytic challenge. We propose a functional multiple imputation approach modeling longitudinal response profiles as smooth curv...

journal_title：Statistics in medicine

authors： He Y,Yucel R,Raghunathan TE

更新日期：2011-05-10 00:00:00

abstract：:Confounding is a major concern in observational studies. To adjust for confounding bias, the potential confounder(s) for a study must first be identified and measured. But this is not always possible. The unmeasured factors may also exhibit effect modification, and this further complicates the situation. In this paper...

journal_title：Statistics in medicine

authors： Lee WC

更新日期：2011-04-30 00:00:00

abstract：:The use of logistic models for independent binary data has relied first on asymptotic theory and later on exact distributions for small samples. However, the use of logistic models for dependent analysis based on exact analysis is not as common. Moreover, attention is usually given to one-stage clustering. In this pap...

journal_title：Statistics in medicine

authors： Troxler S,Lalonde T,Wilson JR

更新日期：2011-04-15 00:00:00

abstract：:In vaccine safety studies, subjects are considered at increased risk for adverse events for a period of time after vaccination known as risk window. To our knowledge, risk windows for vaccine safety studies have tended to be pre-defined and not to use information from the current study. Inaccurate specification of the...

journal_title：Statistics in medicine

authors： Xu S,Zhang L,Nelson JC,Zeng C,Mullooly J,McClure D,Glanz J

更新日期：2011-03-30 00:00:00

abstract：:In the analysis of survival data, there are often competing events that preclude an event of interest from occurring. Regression analysis with competing risks is typically undertaken using a cause-specific proportional hazards model. However, modern alternative methods exist for the analysis of the subdistribution haz...

journal_title：Statistics in medicine

authors： Lau B,Cole SR,Gange SJ

更新日期：2011-03-15 00:00:00