{"title":"Nonparametric inference for the localization receiver operating characteristic curve and its extension to free-response image localization tasks.","authors":"Kaiyuan Liu, Xiao-Hua Zhou","doi":"10.1177/09622802261468028","DOIUrl":"10.1177/09622802261468028","url":null,"abstract":"<p><p>The localization receiver operating characteristic (LROC) and the free-response receiver operating characteristic (FROC) curves are popular methods for evaluating the performance of diagnostic tests concerning detecting and locating lesions. However, the existing LROC and FROC curves have some limitations in their definition and estimation methods. In this article, we extend the LROC curve to the free-response tasks where each case can be marked with multiple suspicious locations and propose a nonparametric estimation of the LROC curve to compensate for the limitations of existing LROC and FROC curves. We derive the asymptotic properties for our estimators and propose a bootstrap method for constructing confidence bands for the proposed LROC curve. Simulations are conducted to compare the proposed LROC curve with the existing AFROC curve and to examine the theoretical results. Finally, we apply our method to evaluate the performance of a diagnostic test investigating AI-assisted pulmonary nodule diagnosis.</p>","PeriodicalId":22038,"journal":{"name":"Statistical Methods in Medical Research","volume":" ","pages":"1932-1958"},"PeriodicalIF":2.4,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148424428","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Nonparametric change-point control charts for joint monitoring of mean and covariance with application to medical imaging data.","authors":"Guojun Liu, Jyun-You Chiang, Wen Liu, Yi Li","doi":"10.1177/09622802261466468","DOIUrl":"10.1177/09622802261466468","url":null,"abstract":"<p><p>Monitoring medical imaging data is increasingly important in healthcare because image-derived quantitative features provide valuable information for assessing disease progression, diagnostic quality, and process stability. However, such data are often feature-rich, distributionally complex, and limited in sample size, and existing methods do not always provide a unified way for retrospectively monitoring joint changes in mean and covariance without relying on strong parametric assumptions. Motivated by these challenges, this paper develops a Phase I nonparametric change-point monitoring framework for individual observations. The framework combines existing high-dimensional two-sample statistics for mean and covariance changes into two control chart schemes, whose control limits are determined through simulation. A post-signal diagnostic procedure is also presented to estimate the change-point location, identify whether the detected shift occurs in the mean, the covariance, or both, and screen potentially affected variables. An extensive simulation study considering various distributional models shows that the proposed charts preserve the nominal in-control false alarm probability, achieve favorable out-of-control detection power, and yield informative post-signal diagnostic results. Finally, a real-world colposcopy dataset is used to illustrate the practical applicability of the proposed framework for the retrospective monitoring of medical imaging data.</p>","PeriodicalId":22038,"journal":{"name":"Statistical Methods in Medical Research","volume":" ","pages":"1959-1979"},"PeriodicalIF":2.4,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148424408","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Evaluating and testing for actionable treatment effect heterogeneity.","authors":"Mahsa Ashouri, Nicholas C Henderson","doi":"10.1177/09622802261470081","DOIUrl":"10.1177/09622802261470081","url":null,"abstract":"<p><p>Developing tools for estimating heterogeneous treatment effects (HTEs) and individualized treatment effects has been an area of active research in recent years. While these tools have proven to be useful in many contexts, a concern when deploying such methods is the degree to which incorporating HTE into a prediction model provides an advantage over predictive methods that do not allow for heterogeneity in treatment effect across individuals. To address this concern, we propose a procedure that evaluates the extent to which an HTE model provides a predictive advantage. Specifically, our procedure targets the gain in predictive performance from using a flexible predictive model incorporating HTE versus an alternative partial linear model which is similar to the HTE-utilizing model except that it is constrained to not allow heterogeneity in treatment effect. By drawing upon recent work in using nested cross-validation techniques for prediction error inference, we generate confidence intervals for this measure of gain in predictive performance, which allows one to directly calculate the level at which one is confident of a substantial HTE-modeling gain in prediction-a quantity that we refer to as the predictive HTE <math><mi>p</mi></math>-value. Our procedure is generic and can be directly used to assess the benefit of modeling HTE for any method that incorporates treatment effect heterogeneity.</p>","PeriodicalId":22038,"journal":{"name":"Statistical Methods in Medical Research","volume":" ","pages":"2001-2023"},"PeriodicalIF":2.4,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148563025","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gustavo H A Pereira, Jeremias Leao, Manoel Santos-Neto, Jianwen Cai
{"title":"A more interpretable regression model for count data with excess of zeros.","authors":"Gustavo H A Pereira, Jeremias Leao, Manoel Santos-Neto, Jianwen Cai","doi":"10.1177/09622802261468025","DOIUrl":"10.1177/09622802261468025","url":null,"abstract":"<p><p>Count data are common in medical research. When these data have more zeros than expected by the most used count distributions, it is common to employ a zero-inflated regression model. However, the interpretability of these models is much lower than the most used count regression models. We present a more interpretable regression model that estimates the mean event rate and models covariate-dependent dispersion directly. Additionally, the dispersion parameter can be interpreted as an index of clumping, a control parameter for overdispersion. We discuss inferential and diagnostic tools and perform a Monte Carlo simulation study to evaluate the performance of the maximum likelihood estimator. Finally, the usefulness of the proposed regression model is illustrated through an application on antenatal care visits.</p>","PeriodicalId":22038,"journal":{"name":"Statistical Methods in Medical Research","volume":" ","pages":"1897-1909"},"PeriodicalIF":2.4,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148424323","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jinhong Cui, Xiaoxiao Zhou, Melissa J Smith, Andrew Sims, Justin M Leach, D Leann Long, Nengjun Yi
{"title":"Bayesian mediation analysis for zero-inflated mediator.","authors":"Jinhong Cui, Xiaoxiao Zhou, Melissa J Smith, Andrew Sims, Justin M Leach, D Leann Long, Nengjun Yi","doi":"10.1177/09622802261468022","DOIUrl":"10.1177/09622802261468022","url":null,"abstract":"<p><p>Mediation analysis is a powerful tool for exploring the causal relationships between exposures and outcomes that are mediated by intermediate variables. In this paper, we propose a flexible Bayesian mediation analysis framework to accommodate zero-inflated mediators, compatible with a wide range of outcome distributions. This novel technique employs Bayesian models for both the mediator and the outcome, utilizing Markov Chain Monte Carlo algorithms for parameter estimation. While addressing the challenges posed by an excess of zeros, we further decompose the mediation effects into components influenced by either the probability of zero or the mean of the non-zero distribution in the mediator. An associated R package <b><i>mediationBayes</i></b> (https://github.com/jhcuibst/mediationBayes.git) has been developed to facilitate the application of this framework. Through comprehensive simulation studies, we demonstrate that our method outperforms alternatives in terms of the accuracy of point estimates, coverage probabilities, and the precision of the mediation effects decomposition. We further illustrate the practical applicability of our method by conducting an analysis on the REasons for Geographic And Racial Differences in Stroke Study to investigate the mediating influence of smoking pack-years on the association between educational levels and incident hypertension, where mediation effects are quantified on a risk ratio scale for binary outcomes.</p>","PeriodicalId":22038,"journal":{"name":"Statistical Methods in Medical Research","volume":" ","pages":"1882-1896"},"PeriodicalIF":2.4,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148449600","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Improved survival analysis with shrinkage Kibria-Lukman estimators in the Cox model: Application to lung cancer data.","authors":"Solmaz Seifollahi, Mohammad Arashi","doi":"10.1177/09622802261423186","DOIUrl":"10.1177/09622802261423186","url":null,"abstract":"<p><p>The Cox proportional hazards regression model is a widely used and valuable tool for modeling survival time with predictors, however its performance can deteriorate in the presence of multicollinearity. It can lead to unreliable estimates from the maximum partial likelihood estimator. In this paper, we introduce enhanced shrinkage estimators based on the Kibria-Lukman approach to obtain more efficient coefficient estimates. Specifically, we develop linear shrinkage, Stein and its positive counterpart, pretest, and shrinkage pretest estimators that incorporate prior information about model coefficients. We derive their asymptotic bias and variance properties and evaluate their performance through extensive Monte Carlo simulations. The results demonstrate significant improvements, highlighting the practical advantages of these methods for applied researchers. We also illustrate the application of our proposed estimators using a lung cancer dataset.</p>","PeriodicalId":22038,"journal":{"name":"Statistical Methods in Medical Research","volume":" ","pages":"1787-1805"},"PeriodicalIF":2.4,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147345367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Estimating the effects of treatment regimes over the course of chronic disease: A multi-state causal framework with baseline confounding.","authors":"Ming Ding","doi":"10.1177/09622802261445822","DOIUrl":"10.1177/09622802261445822","url":null,"abstract":"<p><p>The development of chronic disease is a long-term process involving multiple endpoints. Although multi-state Cox models can estimate state-specific survival risks over time, they are not well suited for comparing the effectiveness of treatment regimes. A discrete-time split-state framework has been proposed, which divides disease states into substates by conditioning on past history. As this framework is both \"memoryless\" and \"memorable,\" the transition rates can be synthesized into summary measures, multimorbidity-adjusted life year (MALY) and substate-specific life year (SSLY). Building on this framework, we propose to investigate the causal effects of static and dynamic treatment regimes over the disease course under the assumptions of constant baseline confounders and instantaneous effects of interventions on transition rates. We identify the optimal treatment regime as the one that maximizes MALY and use SSLY to elucidate the mechanisms of how treatments influence disease progression. In the application, we identified the optimal weight targets in the ARIC study by modeling the disease course in healthy, at-metabolic-risk, coronary heart disease, heart failure, and mortality states. The estimated MALY was 1.80 years higher (95% CI: 0.62, 2.78) under regime \"Normal weight initially and change to overweight if age >65 y\" compared to regime \"Normal weight across all states.\" SSLY decomposition indicates that this gain arises from increased life year in all substates except the healthy state. In summary, our method provides a framework to evaluate the health benefits of treatment regimes over the disease course and has the potential to improve the precision prevention of chronic diseases.</p>","PeriodicalId":22038,"journal":{"name":"Statistical Methods in Medical Research","volume":" ","pages":"1806-1817"},"PeriodicalIF":2.4,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13558798/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147975660","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kenneth M Lee, Andrew B Forbes, Jessica Kasza, Andrew Copas, Brennan C Kahan, Paul J Young, Michael O Harhay, Fan Li
{"title":"What is estimated in cluster randomized crossover trials with informative sizes? A survey of estimands and common estimators.","authors":"Kenneth M Lee, Andrew B Forbes, Jessica Kasza, Andrew Copas, Brennan C Kahan, Paul J Young, Michael O Harhay, Fan Li","doi":"10.1177/09622802261470087","DOIUrl":"10.1177/09622802261470087","url":null,"abstract":"<p><p>The cluster randomized crossover (CRXO) trial, among other multi-period cluster randomized trial designs, can target average treatment effect (ATE) estimands that equally weigh the contributions of individuals (iATE), clusters (cATE), cluster-periods (cpATE), or periods (pATE). With these weighted ATE estimands, we define different forms of informative sizes, where the treatment effects vary according to cluster, period, and/or cluster-period sizes, causing these estimands to differ. Under such informative sizes, we survey which of the unweighted, inverse cluster-period size weighted, inverse cluster size weighted, and inverse period size weighted: (i) independence estimating equation, (ii) fixed effects model, (iii) exchangeable mixed effects model, and (iv) nested exchangeable mixed effects model treatment effect estimators are consistent for the aforementioned estimands in cross-sectional CRXO designs with continuous outcomes. We demonstrate that with informative sizes, the unweighted and weighted nested exchangeable mixed effects model estimators are not consistent for any meaningful estimand and can yield biased results. In contrast, the unweighted and weighted independence estimating equation, and under specific scenarios, the fixed effects model and exchangeable mixed effects model, can yield consistent and empirically unbiased estimators for meaningful estimands in CRXO trials.</p>","PeriodicalId":22038,"journal":{"name":"Statistical Methods in Medical Research","volume":" ","pages":"1980-2000"},"PeriodicalIF":2.4,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13558815/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148697867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Stratification in small randomised clinical trials and analysis of covariance: Some simple theory and recommendations.","authors":"Stephen Senn, Franz König, Martin Posch","doi":"10.1177/09622802261454833","DOIUrl":"10.1177/09622802261454833","url":null,"abstract":"<p><p>A simple device for balancing for a continuous covariate in clinical trials is to stratify by whether the covariate is above or below some target value, typically the predicted median. The object is to improve balance of the covariate and hence efficiency of the treatment estimate particularly if the trial is small, as may be the case if the disease in question is rare. This raises an issue as to which model should be used for modelling the effect of treatment on the outcome variable, <i>Y</i>. Should one fit, the stratum indicator, <i>S</i>, the continuous covariate, <i>X</i>, both or neither? When a covariate is added to a linear model there are three consequences for inference: (a) the mean square error effect, (b) the variance inflation factor and (c) second order precision. We consider that it is valuable to consider these three factors separately, even if, ultimately, it is their joint effect that matters. We present some simple theory, concentrating in particular on the variance inflation factor, that may be used to guide trialists in their choice of model. We also consider the case where the precise form of the relationship between the outcome and the covariate is not known. We conclude by recommending that the continuous covariate should always be in the model but that, depending on circumstances, there may be some justification in fitting the stratum indicator also.</p>","PeriodicalId":22038,"journal":{"name":"Statistical Methods in Medical Research","volume":" ","pages":"1838-1856"},"PeriodicalIF":2.4,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13558804/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148679985","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A flexible rank-based framework for individualized treatment selection with mixed-type multivariate outcomes.","authors":"Chathura Siriwardhana, Bakeerathan Gunaratnam, Karunarathna Bandara Kulasekera","doi":"10.1177/09622802261454791","DOIUrl":"10.1177/09622802261454791","url":null,"abstract":"<p><p>Personalized treatment selection is often based on a single primary endpoint, even though complex diseases are typically monitored using multiple, heterogeneous outcomes. We develop a rank-based framework for individualized treatment selection that accommodates mixed collections of continuous, ordinal, binary, and right-censored survival outcomes. For each outcome and treatment, we summarize the conditional outcome distribution given patient covariates using clinically meaningful parameters, including conditional quantiles, survival probabilities, and tail probabilities at ordered thresholds, and assemble these summaries across treatment arms into vectors with a common structure. Each summary component induces a ranking of the treatments, and discrepancies between outcome-specific rankings and candidate ranking vectors are quantified using a Mahalanobis-type distance that incorporates user-specified outcome weights and an empirically estimated scaling matrix. The optimal treatment is defined as the arm with the most favorable overall rank. Outcome summaries are estimated using flexible tree-based ensemble methods, although other regression or machine-learning tools can be used without altering the decision rule. Monte Carlo simulations across a range of scenarios show reasonably high probabilities of correct treatment selection, with performance improving as the signal-to-noise ratio increases and only mildly affected by the choice of outcome weights. We illustrate the method using data from an AIDS clinical trial, deriving individualized antiretroviral regimen recommendations that balance CD4 response, CD4/CD8 ratio, and a composite time-to-event endpoint.</p>","PeriodicalId":22038,"journal":{"name":"Statistical Methods in Medical Research","volume":" ","pages":"1818-1837"},"PeriodicalIF":2.4,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148472983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}