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Rabe-Hesketh S and Skrondal A, Multilevel and Longitudinal Modeling Using Stata, Volume I: Continuous Responses
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Source: Statistical Methods in Medical Research - November 15, 2016 Category: Statistics Tags: Book review Source Type: research

Comments on propensity score matching following multiple imputation
(Source: Statistical Methods in Medical Research)
Source: Statistical Methods in Medical Research - November 15, 2016 Category: Statistics Authors: Penning de Vries, B., Groenwold, R. Tags: Letters to the editor Source Type: research

Applying compositional data methodology to nutritional epidemiology
The purpose of epidemiological studies of nutrition and disease is to investigate the effects of specific dietary components regardless of total energy intake, but this is sometimes hampered by the compositional nature of dietary data. Compositional data are those that measure parts of a whole, such as percentages or proportions, and particular methodologies have been developed to allow their statistical analysis and theoretical and practical applications in various sciences. This paper describes the use of a compositional data perspective for statistical analyses in the field of nutritional epidemiology. The approach is b...
Source: Statistical Methods in Medical Research - November 15, 2016 Category: Statistics Authors: Leite, M. L. C. Tags: Articles Source Type: research

Logistic regression for dichotomized counts
Sometimes there is interest in a dichotomized outcome indicating whether a count variable is positive or zero. Under this scenario, the application of ordinary logistic regression may result in efficiency loss, which is quantifiable under an assumed model for the counts. In such situations, a shared-parameter hurdle model is investigated for more efficient estimation of regression parameters relating to overall effects of covariates on the dichotomous outcome, while handling count data with many zeroes. One model part provides a logistic regression containing marginal log odds ratio effects of primary interest, while an an...
Source: Statistical Methods in Medical Research - November 15, 2016 Category: Statistics Authors: Preisser, J. S., Das, K., Benecha, H., Stamm, J. W. Tags: Articles Source Type: research

A hybrid Bayesian hierarchical model combining cohort and case-control studies for meta-analysis of diagnostic tests: Accounting for partial verification bias
To account for between-study heterogeneity in meta-analysis of diagnostic accuracy studies, bivariate random effects models have been recommended to jointly model the sensitivities and specificities. As study design and population vary, the definition of disease status or severity could differ across studies. Consequently, sensitivity and specificity may be correlated with disease prevalence. To account for this dependence, a trivariate random effects model had been proposed. However, the proposed approach can only include cohort studies with information estimating study-specific disease prevalence. In addition, some diagn...
Source: Statistical Methods in Medical Research - November 15, 2016 Category: Statistics Authors: Ma, X., Chen, Y., Cole, S. R., Chu, H. Tags: Articles Source Type: research

Longitudinal data subject to irregular observation: A review of methods with a focus on visit processes, assumptions, and study design
When data are collected longitudinally, measurement times often vary among patients. This is of particular concern in clinic-based studies, for example retrospective chart reviews. Here, typically no two patients will share the same set of measurement times and moreover, it is likely that the timing of the measurements is associated with disease course; for example, patients may visit more often when unwell. While there are statistical methods that can help overcome the resulting bias, these make assumptions about the nature of the dependence between visit times and outcome processes, and the assumptions differ across meth...
Source: Statistical Methods in Medical Research - November 15, 2016 Category: Statistics Authors: Pullenayegum, E. M., Lim, L. S. Tags: Articles Source Type: research

Individualized dynamic prediction of prostate cancer recurrence with and without the initiation of a second treatment: Development and validation
With the emergence of rich information on biomarkers after treatments, new types of prognostic tools are being developed: dynamic prognostic tools that can be updated at each new biomarker measurement. Such predictions are of interest in oncology where after an initial treatment, patients are monitored with repeated biomarker data. However, in such setting, patients may receive second treatments to slow down the progression of the disease. This paper aims to develop and validate dynamic individual predictions that allow the possibility of a new treatment in order to help understand the benefit of initiating new treatments ...
Source: Statistical Methods in Medical Research - November 15, 2016 Category: Statistics Authors: Sene, M., Taylor, J. M., Dignam, J. J., Jacqmin-Gadda, H., Proust-Lima, C. Tags: Articles Source Type: research

Increasing efficiency for estimating treatment-biomarker interactions with historical data
Detecting a treatment–biomarker interaction, which is a task better suited for large sample sizes, in a phase II trial, which has a small sample size, is challenging. In this paper, we investigate how two plausibly available sources of historical data may contain partial information to help estimate the treatment–biomarker interaction parameter in a randomized phase II study. The parameter is not identified in either historical dataset alone; nonetheless, both can provide some information about the parameter and, consequently, increase the precision of its estimate. To illustrate the potential for gains in effi...
Source: Statistical Methods in Medical Research - November 15, 2016 Category: Statistics Authors: Boonstra, P. S., Taylor, J. M., Mukherjee, B. Tags: Articles Source Type: research

Choice of agreement indices for assessing and improving measurement reproducibility in a core laboratory setting
Clinical core laboratories, such as Echocardiography core laboratories, are increasingly used in clinical studies with imaging outcomes as primary, secondary, or surrogate endpoints. While many factors contribute to the quality of measurements of imaging variables, an essential step in ensuring the value of imaging data includes formal assessment and control of reproducibility via intra-observer and inter-observer reliability. There are many different agreement/reliability indices in the literature. However, different indices may lead to different conclusions and it is not clear which index is the preferred choice as an ov...
Source: Statistical Methods in Medical Research - November 15, 2016 Category: Statistics Authors: Barnhart, H. X., Yow, E., Crowley, A. L., Daubert, M. A., Rabineau, D., Bigelow, R., Pencina, M., Douglas, P. S. Tags: Articles Source Type: research

Combining growth curves when a longitudinal study switches measurement tools
When longitudinal studies are performed to investigate the growth of traits in children, the measurement tool being used to quantify the trait may need to change as the subjects’ age throughout the study. Changing the measurement tool at some point in the longitudinal study makes the analysis of that growth challenging which, in turn, makes it difficult to determine what other factors influence the growth rate. We developed a Bayesian hierarchical modeling framework that relates the growth curves per individual for each of the different measurement tools and allows for covariates to influence the shapes of the curves...
Source: Statistical Methods in Medical Research - November 15, 2016 Category: Statistics Authors: Oleson, J. J., Cavanaugh, J. E., Tomblin, J. B., Walker, E., Dunn, C. Tags: Articles Source Type: research

Semi-Markov models for interval censored transient cognitive states with back transitions and a competing risk
Continuous-time multi-state stochastic processes are useful for modeling the flow of subjects from intact cognition to dementia with mild cognitive impairment and global impairment as intervening transient cognitive states and death as a competing risk. Each subject's cognition is assessed periodically resulting in interval censoring for the cognitive states while death without dementia is not interval censored. Since back transitions among the transient states are possible, Markov chains are often applied to this type of panel data. In this manuscript, we apply a semi-Markov process in which we assume that the waiting tim...
Source: Statistical Methods in Medical Research - November 15, 2016 Category: Statistics Authors: Wei, S., Kryscio, R. J. Tags: Articles Source Type: research

Survival estimation in two-phase cohort studies with application to biomarkers evaluation
Two-phase studies are attractive for their economy and efficiency in research settings where large cohorts are available for investigating the prognostic and predictive role of novel genetic and biological factors. In this type of study, information on novel factors is collected only in a convenient subcohort (phase II) drawn from the cohort (phase I) according to a given (optimal) sampling strategy. Estimation of survival in the subcohort needs to account for the design. The Kaplan–Meier method, based on counts of events and of subjects at risk in time, must be applied accounting, with suitable weights, for the samp...
Source: Statistical Methods in Medical Research - November 15, 2016 Category: Statistics Authors: Rebora, P., Valsecchi, M. G. Tags: Articles Source Type: research

Diagnosis using clinical/pathological and molecular information
We describe how this distance works, and we also explain why it may sometimes be preferred. We discuss the choice of the related metric scaling distance and compare it with other proximity measures to include both clinical and genetic information. Furthermore, we comment the choice of the related metric scaling distance when classical clustering or discriminant analysis based on distances are performed and compare the results with more complex cluster or discriminant procedures specially constructed for integrating clinical and molecular information. The use of the related metric scaling distance is illustrated on simulate...
Source: Statistical Methods in Medical Research - November 15, 2016 Category: Statistics Authors: Irigoien, I., Arenas, C. Tags: Articles Source Type: research

A general framework for the use of logistic regression models in meta-analysis
Where individual participant data are available for every randomised trial in a meta-analysis of dichotomous event outcomes, "one-stage" random-effects logistic regression models have been proposed as a way to analyse these data. Such models can also be used even when individual participant data are not available and we have only summary contingency table data. One benefit of this one-stage regression model over conventional meta-analysis methods is that it maximises the correct binomial likelihood for the data and so does not require the common assumption that effect estimates are normally distributed. A second benefit of...
Source: Statistical Methods in Medical Research - November 15, 2016 Category: Statistics Authors: Simmonds, M. C., Higgins, J. P. Tags: Articles Source Type: research

Gene selection for survival data under dependent censoring: A copula-based approach
Dependent censoring arises in biomedical studies when the survival outcome of interest is censored by competing risks. In survival data with microarray gene expressions, gene selection based on the univariate Cox regression analyses has been used extensively in medical research, which however, is only valid under the independent censoring assumption. In this paper, we first consider a copula-based framework to investigate the bias caused by dependent censoring on gene selection. Then, we utilize the copula-based dependence model to develop an alternative gene selection procedure. Simulations show that the proposed procedur...
Source: Statistical Methods in Medical Research - November 15, 2016 Category: Statistics Authors: Emura, T., Chen, Y.-H. Tags: Articles Source Type: research