1,721,031 research outputs found
Permutation-based inference for the AUC: A unified approach for continuous and discontinuous data
No full textWe investigate rank-based studentized permutation methods for the nonparametric Behrens-Fisher problem, that is, inference methods for the area under the ROC curve. We hereby prove that the studentized permutation distribution of the Brunner-Munzel rank statistic is asymptotically standard normal, even under the alternative. Thus, incidentally providing the hitherto missing theoretical foundation for the Neubert and Brunner studentized permutation test. In particular, we do not only show its consistency, but also that confidence intervals for the underlying treatment effects can be computed by inverting this permutation test. In addition, we derive permutation-based range-preserving confidence intervals. Extensive simulation studies show that the permutation-based confidence intervals appear to maintain the preassigned coverage probability quite accurately (even for rather small sample sizes). For a convenient application of the proposed methods, a freely available software package for the statistical software R has been developed. A real data example illustrates the application.German Research Foundation [DFG Br 655/16-1, Ho 1687/9-1, Pa 2409/3-1
Modelling and sample size reestimation for longitudinal count data with incomplete follow up
No full textWe consider modelling and inference as well as sample size estimation and reestimation for clinical trials with longitudinal count data as outcomes. Our approach is general but is rooted in design and analysis of multiple sclerosis trials where lesion counts obtained by magnetic resonance imaging are important endpoints. We adopt a binomial thinning model that allows for correlated counts with marginal Poisson or negative binomial distributions. Methods for sample size planning and blinded sample size reestimation for randomised controlled clinical trials with such outcomes are developed. The models and approaches are applicable to data with incomplete observations. A simulation study is conducted to assess the effectiveness of sample size estimation and blinded sample size reestimation methods. Sample sizes attained through these procedures are shown to maintain the desired study power without inflating the type I error. Data from a recent trial in patients with secondary progressive multiple sclerosis illustrate the modelling approach
Consideration of vocal fold position in unilateral vocal fold paralyses
No full textThe objective of this study was to improve the evaluation of unilateral vocal fold paralyses (uVFP) by means of an area measurement of the glottic plane, which describes the position of the paralysed vocal fold. The area measurements were related to electromyographic findings and clinical outcome (recovery, voice quality). In 56 patients (33 women and 23 men), uVFP were confirmed by endolaryngeal electromyography (EMG) of the paralysed vocal fold and cricothyroid muscles (CT). The EMG response was classified on a 4-point scale (from 0 to 3). Vocal fold position was divided into 'paramedian' and 'intermediate' and additionally quantified by measurement of the glottic area. An 'area quotient' (AQ) was calculated and related to the EMG findings and clinical outcome. Voice qualities were objectified regarding their additive noise (breathiness) and irregularity (roughness) using the 'Gottingen Hoarseness Diagram'. The majority of uVFP was due to iatrogenic lesions. The AQ of classically graduated 'paramedian' and 'intermediate' vocal fold positions was significantly different but did not correlate with objective voice quality values. There were no significant correlations regarding EMG findings, duration or recovery from paralyses. Laryngeal EMG remains the gold standard for verifying uVFP. But EMG did not correlate significantly with AQ or functional outcome of uVFP. The measurement of an AQ is suitable for obtaining continuous data describing the position of paralysed vocal folds beyond the terms 'paramedian' or 'intermediate' and provides the basis for clinical evaluations of diagnostic tools and therapeutic interventions
Semi-quantitative assessment of environmental tobacco smoke exposure and its association with the development of oral squamous cell carcinoma: A pilot study
No full textTwo known major risk factors for oral squamous cell carcinoma are smoking and alcohol consumption. Environmental tobacco smoke (also known as secondhand smoke) has been proven to be associated with the occurrence of lung and breast carcinoma. This study aimed to assess exposure to environmental tobacco smoke and its association with the development of oral squamous cell carcinomas.Open-Access-Publikationsfonds 202
Diagnostic value of alpha-1-fetoprotein (AFP) as a biomarker for hepatocellular carcinoma recurrence after liver transplantation
No full textBlinded sample size reestimation for negative binomial regression with baseline adjustment
No full textIn randomized clinical trials, it is standard to include baseline variables in the primary analysis as covariates, as it is recommended by international guidelines. For the study design to be consistent with the analysis, these variables should also be taken into account when calculating the sample size to appropriately power the trial. Because assumptions made in the sample size calculation are always subject to some degree of uncertainty, a blinded sample size reestimation (BSSR) is recommended to adjust the sample size when necessary. In this article, we introduce a BSSR approach for count data outcomes with baseline covariates. Count outcomes are common in clinical trials and examples include the number of exacerbations in asthma and chronic obstructive pulmonary disease, relapses, and scan lesions in multiple sclerosis and seizures in epilepsy. The introduced methods are based on Wald and likelihood ratio test statistics. The approaches are illustrated by a clinical trial in epilepsy. The BSSR procedures proposed are compared in a Monte Carlo simulation study and shown to yield power values close to the target while not inflating the type I error rate
Correction to: Bone Mineral Density During Treatment with The Janus Kinase Inhibitor Baricitinib in Patients with Rheumatoid Arthritis: A Monocentric Observational Study
No full textTeilprojekt 2 : Schlussbericht (Teilprojekt 2) für das Projekt : Projektlaufzeit: 01.02.2015 bis 31.01.2018 (bis 31.03.2018 nach Verlängerung)
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Results of a German national survey to assess early mobilization versus bed rest in the postoperative management of incidental durotomy during lumbar surgery and the need for a randomized clinical trial
No full textOBJECTIVE Incidental durotomy during degenerative lumbar spine surgeries poses a complex medical challenge. Despite its relatively common occurrence, consensus on its management remains elusive due to the absence of robust, high-level evidence, resulting in significant variations in practice across medical institutions. The aim of this survey was to assess the current practices in Germany regarding early mobilization versus bed rest in the postoperative management of incidental durotomy during lumbar surgery to estimate the need for a randomized clinical trial. METHODS A digital survey titled "Postoperative management of incidental durotomy in lumbar spine surgery" was conducted among 119 neurosurgical departments in Germany. Key questions included the use of bed rest postsurgery, timing of mobilization, and whether the practice depended on the complexity of the surgery or the quality of the dural tear repair. The survey also explored the role of lumbar drains in management and respondents’ potential participation in a multicenter study on the benefits of bed rest. RESULTS Invitations were sent in November 2023, and responses were collected during November and December 2023. A total of 89 (75%) departments completed the survey. Among them, 75% reported using bed rest in the postoperative management of incidental durotomy. For 57%, this practice depends on the complexity of the surgical procedure or the quality of the surgical repair of the dural tear, while 18% apply it independently. Twenty-nine of the 89 departments (33%) answered that mobilization is allowed 24 hours after surgery, 13 departments (15%) allow mobilization after 48 hours, and 19 departments (21%) allow it after 72 hours. Additionally, 34% reported using a lumbar drain in cases of persistent postoperative CSF leakage, 36% use it for secondary surgical revision, and 30% do not use it in either case. Furthermore, 55 departments (62%) expressed potential interest in participating in a multicenter randomized trial addressing the postoperative management of incidental durotomy. CONCLUSIONS The postoperative management of incidental durotomy during lumbar surgery exhibits significant variation across neurosurgical departments in Germany. Postoperative bed rest remains a common practice. To evaluate the true benefits of bed rest, a randomized multicenter study is recommended. A summary proposal for such a study is presented to address this need
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