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Biometrical Journal. Biometrische Zeitschrift

Andrea Callegaro, Cheikh Ndour, Emmanuel Aris, Catherine Legrand
A well-known problem in classical two-tailed hypothesis testing is that P-values go to zero when the sample size goes to infinity, irrespectively of the effect size. This pitfall can make the testing of data consisting of large sample sizes potentially unreliable. In this note, we propose to test for relevant differences to overcome this issue. We illustrate the proposed test a on real data set of about 40 million privately insured patients.
November 11, 2018: Biometrical Journal. Biometrische Zeitschrift
Samuel T Hsiao, Lingyun Liu, Cyrus R Mehta
Clinical trials with adaptive sample size reassessment based on an unblinded analysis of interim results are perhaps the most popular class of adaptive designs (see Elsäßer et al., 2007). Such trials are typically designed by prespecifying a zone for the interim test statistic, termed the promising zone, along with a decision rule for increasing the sample size within that zone. Mehta and Pocock (2011) provided some examples of promising zone designs and discussed several procedures for controlling their type-1 error...
November 8, 2018: Biometrical Journal. Biometrische Zeitschrift
María J Rufo, Jacinto Martín, Carlos J Pérez, Sandra Paniagua
Vocal fold nodules are recognized as an occupational disease for all collective of workers performing activities for which maintained and continued use of voice is required. Computer-aided systems based on features extracted from voice recordings have been considered as potential noninvasive and low cost tools to diagnose some voice-related diseases. A Bayesian decision analysis approach has been proposed to classify university lectures in three levels of risk: low, medium, and high, based on the information provided by acoustic features extracted from healthy controls and people suffering from vocal fold nodules...
November 8, 2018: Biometrical Journal. Biometrische Zeitschrift
Leonidas E Bantis, Christos T Nakas, Benjamin Reiser
Evaluation of the overall accuracy of biomarkers might be based on average measures of the sensitivity for all possible specificities -and vice versa- or equivalently the area under the receiver operating characteristic (ROC) curve that is typically used in such settings. In practice clinicians are in need of a cutoff point to determine whether intervention is required after establishing the utility of a continuous biomarker. The Youden index can serve both purposes as an overall index of a biomarker's accuracy, that also corresponds to an optimal, in terms of maximizing the Youden index, cutoff point that in turn can be utilized for decision making...
November 8, 2018: Biometrical Journal. Biometrische Zeitschrift
Shizhong Xu
Estimation of variance components in linear mixed models is important in clinical trial and longitudinal data analysis. It is also important in animal and plant breeding for accurately partitioning total phenotypic variance into genetic and environmental variances. Restricted maximum likelihood (REML) method is often preferred over the maximum likelihood (ML) method for variance component estimation because REML takes into account the lost degree of freedom resulting from estimating the fixed effects. The original restricted likelihood function involves a linear transformation of the original response variable (a collection of error contrasts)...
November 2, 2018: Biometrical Journal. Biometrische Zeitschrift
John S Preisser, Gul Inan, James M Powers, Haitao Chu
The meta-analysis of diagnostic accuracy studies is often of interest in screening programs for many diseases. The typical summary statistics for studies chosen for a diagnostic accuracy meta-analysis are often two dimensional: sensitivities and specificities. The common statistical analysis approach for the meta-analysis of diagnostic studies is based on the bivariate generalized linear-mixed model (BGLMM), which has study-specific interpretations. In this article, we present a population-averaged (PA) model using generalized estimating equations (GEE) for making inference on mean specificity and sensitivity of a diagnostic test in the population represented by the meta-analytic studies...
October 29, 2018: Biometrical Journal. Biometrische Zeitschrift
Le Thi Phuong Thao, Ronald Geskus
Many approaches for variable selection with multiply imputed data in the development of a prognostic model have been proposed. However, no method prevails as uniformly best. We conducted a simulation study with a binary outcome and a logistic regression model to compare two classes of variable selection methods in the presence of MI data: (I) Model selection on bootstrap data, using backward elimination based on AIC or lasso, and fit the final model based on the most frequently (e.g. <mml:math xmlns:mml="http://www...
October 23, 2018: Biometrical Journal. Biometrische Zeitschrift
Hui-Min Lin, Haiyan Xu, Ying Ding, Jason C Hsu
Targeted therapies are becoming more common. In targeted therapy development, suppose its companion diagnostic test divides patients into a marker-positive subgroup and its complementary marker-negative subgroup. To find the right patient population for the therapy to target, inference on efficacy in the marker-positive and marker-negative subgroups as well as efficacy in the overall mixture population are all of interest. Depending on the type of clinical endpoints, inference on mixture population can be nontrivial and commonly used efficacy measures may not be suitable for a mixture population...
October 23, 2018: Biometrical Journal. Biometrische Zeitschrift
Sara Franceschi, Marzia Marcheselli, Stefania Naddeo, Caterina Pisani
The estimation of the values of a variable at any point of a study area is performed using Bernstein polynomials when the sampling scheme is implemented by selecting a point in each polygon of a regular grid overimposed onto the area. The evaluation of the precision of the resulting estimates is investigated under a completely design-based framework. Moreover, as the main contribution to the mean squared error of the Bernstein-type estimator is due to the bias, also a pseudo-jackknife estimator is proposed...
October 22, 2018: Biometrical Journal. Biometrische Zeitschrift
Philippe Lambert, Vincent Bremhorst
The promotion time cure model is a survival model acknowledging that an unidentified proportion of subjects will never experience the event of interest whatever the duration of the follow-up. We focus our interest on the challenges raised by the strong posterior correlation between some of the regression parameters when the same covariates influence long- and short-term survival. Then, the regression parameters of shared covariates are strongly correlated with, in addition, identification issues when the maximum follow-up duration is insufficiently long to identify the cured fraction...
October 22, 2018: Biometrical Journal. Biometrische Zeitschrift
Isaac Gravestock, Leonhard Held
Incorporating historical information into the design and analysis of a new clinical trial has been the subject of much recent discussion. For example, in the context of clinical trials of antibiotics for drug resistant infections, where patients with specific infections can be difficult to recruit, there is often only limited and heterogeneous information available from the historical trials. To make the best use of the combined information at hand, we consider an approach based on the multiple power prior that allows the prior weight of each historical study to be chosen adaptively by empirical Bayes...
October 16, 2018: Biometrical Journal. Biometrische Zeitschrift
Janine Witte, Vanessa Didelez
When causal effects are to be estimated from observational data, we have to adjust for confounding. A central aim of covariate selection for causal inference is therefore to determine a set that is sufficient for confounding adjustment, but other aims such as efficiency or robustness can be important as well. In this paper, we review six general approaches to covariate selection that differ in the targeted type of adjustment set. We discuss and illustrate their advantages and disadvantages using causal diagrams...
October 10, 2018: Biometrical Journal. Biometrische Zeitschrift
Hans-Peter Piepho, Volker Michel, Emlyn Williams
Row-column designs allow error control in field experiments by blocking in two dimensions. While this strategy can capture spatial heterogeneity aligned with blocks and account for effects due to the farming operations along rows and columns, it suffers from the occasional clustered occurrence of several replications of the same treatment. This property of classical row-column designs has hampered their more widespread use in practice. A further issue of practical importance is the degree of neighbor balance of a design, that is, the frequency of adjacencies of pairs of treatments...
October 5, 2018: Biometrical Journal. Biometrische Zeitschrift
Laura Antolini, Elena Tassistro, Maria Grazia Valsecchi, Davide Paolo Bernasconi
The availability of novel biomarkers in several branches of medicine opens room for refining prognosis by adding factors on top of those having an established role. It is accepted that the impact of novel factors should not rely solely on regression coefficients and their significance but also on predictive power measures, such as Brier score and ROC-based quantities. However, novel factors that are promising at the exploratory stage often result in disappointingly low impact in the predictive power. This motivated the proposal of the net reclassification improvement and the integrated discrimination improvement, as direct measures of predictive power gain due to additional factors based on the concept of reclassification tables...
October 5, 2018: Biometrical Journal. Biometrische Zeitschrift
Yougui Wu
McNemars test is often used to compare two proportions estimated from paired observations. When the observations are sampled in clusters, adjustment is needed to ensure that the size of McNemars test does not exceed the nominal level. Eliasziw and Donner (1991) developed an adjustment to McNemars test that involves first estimating the correlation between discordant pairs within a cluster, then using the estimate of the correlation to adjust the usual McNemar's test statistic. Gönen (2004) derived two approximations for calculating the power and sample size for the adjusted McNemar's test...
October 4, 2018: Biometrical Journal. Biometrische Zeitschrift
Heather J Whitaker, Colin D Steer, C Paddy Farrington
The self-controlled case series method assumes that adverse outcomes arise according to a non-homogeneous Poisson process. This implies that it is applicable to independent recurrent outcomes. However, the self-controlled case series method may also be applied to unique, non-recurrent outcomes or first outcomes only, in the limit where these become rare. We investigate this rare outcome assumption when the self-controlled case series method is applied to non-recurrent outcomes. We study this requirement analytically and by simulation, and quantify what is meant by 'rare' in this context...
October 3, 2018: Biometrical Journal. Biometrische Zeitschrift
Elvira M Erhardt, Moreno Ursino, Jeike Biewenga, Tom Jacobs, Mauro Gasparini
The primary goal of "in vitro-in vivo correlation" (IVIVC) is the reliable prediction of the in vivo serum concentration-time course, based on the in vitro drug dissolution or release profiles. IVIVC methods are particularly appropriate for formulations that are released over an extended period of time or with a lag in absorption and may support approving a change in formulation of a drug without additional bioequivalence trials in human subjects. Most of the current IVIVC models are assessed using frequentist methods, such as linear regression, based on averaged data and entail complex and potentially unstable mathematical deconvolution...
September 27, 2018: Biometrical Journal. Biometrische Zeitschrift
Brian Knaeble, Julian Chan
This article introduces a new condition based on odds ratios for sensitivity analysis. The analysis involves the average effect of a treatment or exposure on a response or outcome with estimates adjusted for and conditional on a single, unmeasured, dichotomous covariate. Results of statistical simulations are displayed to show that the odds ratio condition is as reliable as other commonly used conditions for sensitivity analysis. Other conditions utilize quantities reflective of a mediating covariate. The odds ratio condition can be applied when the covariate is a confounding variable...
September 26, 2018: Biometrical Journal. Biometrische Zeitschrift
David Hajage, Guillaume Chauvet, Lisa Belin, Alexandre Lafourcade, Florence Tubach, Yann De Rycke
Propensity score (PS) methods are widely used in observational studies for evaluating marginal treatment effects. PS-weighting is a popular PS-based method that allows for estimating both the average treatment effect on the overall population (ATE) and the average treatment effect on the treated population (ATT). Previous research has shown that the variance of the treatment effect is accurately estimated only if the variance estimator takes into account the fact that the propensity score is itself estimated from the available data in a first step of the analysis...
September 26, 2018: Biometrical Journal. Biometrische Zeitschrift
Irene Schmidtmann, Stavros Konstantinides, Harald Binder
In clinical trials with patients in a critical state, death may preclude measurement of a quantitative endpoint of interest, and even early measurements, for example for intention-to-treat analysis, may not be available. For example, a non-negligible proportion of patients with acute pulmonary embolism will die before 30 day measurements on the efficacy of thrombolysis can be obtained. As excluding such patients may introduce bias, alternative analyses, and corresponding means for sample size calculation are needed...
September 19, 2018: Biometrical Journal. Biometrische Zeitschrift
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