Abstract:
:Antimicrobial resistance has become one of the main public health burdens of the last decades, and monitoring the development and spread of non-wild-type isolates has therefore gained increased interest. Monitoring is performed based on the minimum inhibitory concentration (MIC) values, which are collected through the application of dilution experiments. In order to account for the unobserved population heterogeneity of wild-type and non-wild-type isolates, mixture models are extremely useful. Instead of estimating the entire mixture globally, it was our major aim to provide an estimate for the wild-type first component only. The characteristics of this first component are not expected to change over time, once the wild-type population has been confidently identified for a given antimicrobial. With this purpose, we developed a new method based on the multinomial distribution, and we carry out a simulation study to study the properties of the new estimator. Because the new approach fits within the likelihood framework, we can compare distinct distributional assumptions in order to determine the most suitable distribution for the wild-type population. We determine the optimal parameters based on the AIC criterion, and attention is also paid to the model-averaged approach using the Akaike weights. The latter is thought to be very suitable to derive specific characteristics of the wild-type distribution and to determine limits for the wild-type MIC range. In this way, the new method provides an elegant means to compare distinct distributional assumptions and to quantify the wild-type MIC distribution of specific antibiotic-bacterium combinations.
journal_name
Stat Medjournal_title
Statistics in medicineauthors
Jaspers S,Aerts M,Verbeke G,Beloeil PAdoi
10.1002/sim.5939subject
Has Abstractpub_date
2014-01-30 00:00:00pages
289-303issue
2eissn
0277-6715issn
1097-0258journal_volume
33pub_type
杂志文章abstract::The FDA permits marketing of a generic formulation of a drug G for the same indications as a standard preparation S if one can show that G is bioequivalent to S. Present implementation requires convincing evidence that the population mean difference in bioavailability (drug exposure) between the two preparations lies ...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.4780111311
更新日期:1992-09-30 00:00:00
abstract::In biomedical studies and clinical trials, repeated measures are often subject to some upper and/or lower limits of detection. Hence, the responses are either left or right censored. A complication arises when more than one series of responses is repeatedly collected on each subject at irregular intervals over a perio...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.8017
更新日期:2019-03-15 00:00:00
abstract::Risk prediction procedures can be quite useful for the patient's treatment selection, prevention strategy, or disease management in evidence-based medicine. Often, potentially important new predictors are available in addition to the conventional markers. The question is how to quantify the improvement from the new ma...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.5647
更新日期:2013-06-30 00:00:00
abstract::Relative potency is a measure that has been used for many years to summarize the comparison of dose-response curves in parallel line bioassays. When response curves for two preparations are not parallel the traditional definition of relative potency no longer applies. We review the concept of relative potency and show...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/(sici)1097-0258(19970530)16:10<1151::aid-s
更新日期:1997-05-30 00:00:00
abstract::In medical and health studies, heterogeneities in clustered count data have been traditionally modeled by positive random effects in Poisson mixed models; however, excessive zeros often occur in clustered medical and health count data. In this paper, we consider a three-level random effects zero-inflated Poisson model...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.3619
更新日期:2009-08-15 00:00:00
abstract::The "some invalid, some valid instrumental variable estimator" (sisVIVE) is a lasso-based method for instrumental variables (IVs) regression of outcome on an exposure. In principle, sisVIVE is robust to some of the IVs in the analysis being invalid, in the sense of being related to the outcome variable through pathway...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.8066
更新日期:2019-04-30 00:00:00
abstract::In England and Wales, a large-scale multiple statistical surveillance system for infectious disease outbreaks has been in operation for nearly two decades. This system uses a robust quasi-Poisson regression algorithm to identify abberrances in weekly counts of isolates reported to the Health Protection Agency. In this...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.5595
更新日期:2013-03-30 00:00:00
abstract::We develop parametric maximum likelihood methods to adjust for treatment changes during follow-up in order to assess the causal effect of treatment in clinical trials with time-to-event outcomes. The accelerated failure time model of Robins and Tsiatis relates each observed event time to the underlying event time that...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.1618
更新日期:2004-02-28 00:00:00
abstract::Generalized linear models are often assumed to fit propensity scores, which are used to compute inverse probability weighted (IPW) estimators. To derive the asymptotic properties of IPW estimators, the propensity score is supposed to be bounded away from zero. This condition is known in the literature as strict positi...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.7827
更新日期:2018-10-30 00:00:00
abstract::Suppose that two graders classify all eyes in a sample of patients for the presence or absence of a specified abnormality. In the statistical analysis of the data, possible correlation between the observations in the right and left eyes should be taken into account. Recently, general methods have been developed to ana...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.4780122306
更新日期:1993-12-15 00:00:00
abstract::We propose a new, less costly, design to test the equivalence of digital versus analogue mammography in terms of sensitivity and specificity. Because breast cancer is a rare event among asymptomatic women, the sample size for testing equivalence of sensitivity is larger than that for testing equivalence of specificity...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/(sici)1097-0258(19981015)17:19<2219::aid-s
更新日期:1998-10-15 00:00:00
abstract::When data are dichotomous, this paper notes the utility of inverse sampling in establishing equivalence with respect to the risk ratio. This paper develops an exact equivalence test that accounts for the risk ratio under inverse sampling and further discusses the relationship between the exact equivalence test and the...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/(sici)1097-0258(19970815)16:15<1777::aid-s
更新日期:1997-08-15 00:00:00
abstract::We consider the problem of comparing cumulative incidence functions of non-mortality events in the presence of informative coarsening and the competing risk of death. We extend frequentist-based hypothesis tests previously developed for non-informative coarsening and propose a novel Bayesian method based on comparing ...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.3397
更新日期:2008-12-10 00:00:00
abstract::Multivariate random length data occur when we observe multiple measurements of a quantitative variable and the variable number of these measurements is also an observed outcome for each experimental unit. For example, for a patient with coronary artery disease, we may observe a number of lesions in that patient's coro...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/(sici)1097-0258(19990130)18:2<199::aid-sim
更新日期:1999-01-30 00:00:00
abstract::The analysis of repeated measures data can be conducted efficiently using a two-level random coefficients model. A standard assumption is that the within-individual (level 1) residuals are uncorrelated. In some cases, especially where measurements are made close together in time, this may not be reasonable and this ad...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.4780131605
更新日期:1994-08-30 00:00:00
abstract::The standard analysis of clinical trials stratified by centre is to include centres as fixed effects, but if many centres contribute small numbers of patients, this approach results in a loss of power. Assuming no treatment by centre interaction, we used simulation to examine power and coverage of confidence intervals...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.3068
更新日期:2007-12-30 00:00:00
abstract::Group sequential hypothesis testing is now widely used to analyze prospective data. If Monte Carlo simulation is used to construct the signaling threshold, the challenge is how to manage the type I error probability for each one of the multiple tests without losing control on the overall significance level. This paper...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.6805
更新日期:2016-04-30 00:00:00
abstract::We applied a computationally practical form of probit analysis for multiple response variables to data on early childhood development of four psychiatric disorders: disruptive disorders (DD-attention deficit disorders, oppositional defiant disorder, conduct disorder); adjustment disorders (ADJ); emotional disorders (E...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/(sici)1097-0258(19981115)17:21<2487::aid-s
更新日期:1998-11-15 00:00:00
abstract::The problem for assessing biosimilarity and drug interchangeability of follow-on biologics (biosimilar products) is studied. Unlike the generic products, the development of biosimilar products is much more complicated because of fundamental differences in functional structures and manufacturing processes. As a result,...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.5571
更新日期:2013-02-10 00:00:00
abstract::This paper investigates the impact on area life tables of the specification of unobserved frailty. Frailty specification may affect both the regression effects of area and individual level covariates, and lead to changes in the value of summary mortality parameters, such as life expectancy. The paper also investigates...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.4780141703
更新日期:1995-09-15 00:00:00
abstract::We present a method to estimate the time-dependent vaccine efficacy from the cohort-specific vaccination coverage and from data on the vaccination status of cases and apply it to a measles epidemic in Germany which involved 529 cases, 88 of whom were vaccinated and 370 unvaccinated (for the remaining 71 cases the vacc...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.1043
更新日期:2002-08-30 00:00:00
abstract::In this paper, an approach to estimating the cumulative mean function for history process with time dependent covariates and right censored time-to-event variable is developed using the combined technique of joint modeling and inverse probability weighting method. The consistency of proposed estimator is derived. Theo...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.6998
更新日期:2016-11-10 00:00:00
abstract::A mixed effect model is proposed to jointly analyze multivariate longitudinal data with continuous, proportion, count, and binary responses. The association of the variables is modeled through the correlation of random effects. We use a quasi-likelihood type approximation for nonlinear variables and transform the prop...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.7401
更新日期:2017-11-10 00:00:00
abstract::We study the competing risks model and show that the cause j cumulative incidence function integrated from 0 to τ has a natural interpretation as the expected number of life years lost due to cause j before time τ. This is analogous to the τ-restricted mean lifetime, which is the survival function integrated from 0 to...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.5903
更新日期:2013-12-30 00:00:00
abstract::In observational studies with censored data, exposure-outcome associations are commonly measured with adjusted hazard ratios from multivariable Cox proportional hazards models. The difference in restricted mean survival times (RMSTs) up to a pre-specified time point is an alternative measure that offers a clinically m...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.8206
更新日期:2019-09-10 00:00:00
abstract::We studied the problem of testing a hypothesized distribution in survival regression models when the data is right censored and survival times are influenced by covariates. A modified chi-squared type test, known as Nikulin-Rao-Robson statistic, is applied for the comparison of accelerated failure time models. This st...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.7244
更新日期:2017-05-30 00:00:00
abstract::In multivariate network meta-analysis (NMA), the piecemeal nature of the evidence base means that there may be treatment-outcome combinations for which no data is available. Most existing multivariate evidence synthesis models are either unable to estimate the missing treatment-outcome combinations, or can only do so ...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.8668
更新日期:2020-10-30 00:00:00
abstract::Statistical methods are available for performing a meta-analysis when the response variable of interest is the same in each study. Problems arise when studies exploring a common therapeutic question use different patient response types. This article presents statistical methods for combining studies which involve diff...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.4780132313
更新日期:1994-12-15 00:00:00
abstract::The focus of this paper is dietary intervention trials. We explore the statistical issues involved when the response variable, intake of a food or nutrient, is based on self-report data that are subject to inherent measurement error. There has been little work on handling error in this context. A particular feature of...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.7011
更新日期:2016-11-10 00:00:00
abstract::It has been increasingly common to analyze simultaneously repeated measures and time to failure data. In this paper we propose a joint model when the repeated measures are semi-continuous, characterized by the presence of a large portion of zero values, as well as right skewness of non zero (positive) values. Examples...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.3497
更新日期:2009-03-15 00:00:00