Search results for "Sample Size"
showing 10 items of 219 documents
Strategies for Including Patients Recruited During Interim Analysis of Clinical Trials
2007
In clinical trials a periodical check of safety and efficacy data is often needed. For organizational reasons it is rarely desirable to stop a trial during such an interim analysis. Therefore, new study patients are included in the trial while the interim analysis is ongoing. Disregarding the additional information provided by these interim patients would be unsatisfactory, especially for an office of regulatory affairs. Consequently, the rules for group sequential or adaptive decisions must be adjusted to the recruitment of interim patients. In this paper, two strategies for modifying study designs to consider the analysis of interim patients are proposed.
Placebo Therapy in Crohn's disease
2009
The knowledge of the outcome among patients receiving placebo is important for evaluating the response to therapy, for evaluating the natural history of a disease and for calculating the sample size for future clinical trials. In Crohn's disease placebo has been used in therapeutic trials in every relevant setting: active disease, prevention of relapse after induced medical remission and after surgery and fistulising disease. The analysis of the placebo response shows that in every setting there is a high heterogeneity demonstrating mainly that the selection of patients is not often homogeneous and that the outcome criteria used in the trials is not highly reliable. Better selection of pati…
Control of dataset bias in combined Affymetrix cohorts of triple negative breast cancer
2014
AbstractHeterogenous subtypes of breast cancer need to be analyzed separately. Pooling of datasets can provide reasonable sample sizes but dataset bias is an important concern. We assembled a combined dataset of 579 Affymetrix microarrays from triple negative breast cancer (TNBC) in Gene Expression Omnibus (GEO) series GSE31519. We developed a method for selecting comparable datasets and to control for the amount of dataset bias of individual probesets.
Predicting the Significance of Necessity
2019
With Necessary Condition Analysis (NCA), a necessity effect is estimated by calculating the amount of empty space in the upper-left corner in a plot with a predictor X and an outcome Y, and recently a method for testing the statistical significance of the necessity effect through permutation has been proposed. In the present simulation study, this method was found to give significant results already with a very weak true population necessity effect, i.e., exhibit high power, unless the sample size is very small. However, in some situations the significance of the necessity effect tends to increase with increased degree of sufficiency, which is paradoxical for a method whose objective is to …
A cautionary note on the finite sample behavior of maximal reliability.
2019
Several calls have been made for replacing coefficient α with more contemporary model-based reliability coefficients in psychological research. Under the assumption of unidimensional measurement scales and independent measurement errors, two leading alternatives are composite reliability and maximal reliability. Of these two, the maximal reliability statistic, or equivalently Hancock's H, has received a significant amount of attention in recent years. The difference between composite reliability and maximal reliability is that the former is a reliability index for a scale mean (or unweighted sum), whereas the latter estimates the reliability of a scale score where indicators are weighted di…
Protective ventilation with high versus low positive end-expiratory pressure during one-lung ventilation for thoracic surgery (PROTHOR): study protoc…
2018
Postoperative pulmonary complications (PPC) may result in longer duration of in-hospital stay and even mortality. Both thoracic surgery and intraoperative mechanical ventilation settings add considerably to the risk of PPC. It is unclear if one-lung ventilation (OLV) for thoracic surgery with a strategy of intraoperative high positive end-expiratory pressure (PEEP) and recruitment maneuvers (RM) reduces PPC, compared to low PEEP without RM.PROTHOR is an international, multicenter, randomized, controlled, assessor-blinded, two-arm trial initiated by investigators of the PROtective VEntilation NETwork. In total, 2378 patients will be randomly assigned to one of two different intraoperative me…
The all-on-four treatment concept: Systematic review
2017
Objectives To systematically review the literature on the "all-on-four" treatment concept regarding its indications, surgical procedures, prosthetic protocols and technical and biological complications after at least three years in function. Study design The three major electronic databases were screened: MEDLINE (via PubMed), EMBASE, and the Cochrane Library of the Cochrane Collaboration (CENTRAL). In addition, electronic screening was made of the 'grey literature' using the System for Information on Grey Literature in Europe - Open Grey, covering the period from January 2005 up to and including April 2016. Results A total of 728 articles were obtained from the initial screening process. O…
Evaluation of FASP, SP3, and iST Protocols for Proteomic Sample Preparation in the Low Microgram Range
2017
Efficient and reproducible sample preparation is a prerequisite for any robust and sensitive quantitative bottom-up proteomics workflow. Here, we performed an independent comparison between single-pot solid-phase-enhanced sample preparation (SP3), filter-aided sample preparation (FASP), and a commercial kit based on the in-StageTip (iST) method. We assessed their performance for the processing of proteomic samples in the low μg range using varying amounts of HeLa cell lysate (1-20 μg of total protein). All three workflows showed similar performances for 20 μg of starting material. When handling sample sizes below 10 μg, the number of identified proteins and peptides as well as the quantitat…
Comparison of classification methods that combine clinical data and high-dimensional mass spectrometry data
2013
Background The identification of new diagnostic or prognostic biomarkers is one of the main aims of clinical cancer research. Technologies like mass spectrometry are commonly being used in proteomic research. Mass spectrometry signals show the proteomic profiles of the individuals under study at a given time. These profiles correspond to the recording of a large number of proteins, much larger than the number of individuals. These variables come in addition to or to complete classical clinical variables. The objective of this study is to evaluate and compare the predictive ability of new and existing models combining mass spectrometry data and classical clinical variables. This study was co…
Study Design in Medical Research
2009
Medical research studies can be split into five phases—planning, performance, documentation, analysis, and publication (1, 2). Aside from financial, organizational, logistical and personnel questions, scientific study design is the most important aspect of study planning. The significance of study design for subsequent quality, the relability of the conclusions, and the ability to publish a study are often underestimated (1). Long before the volunteers are recruited, the study design has set the points for fulfilling the study objectives. In contrast to errors in the statistical evaluation, errors in design cannot be corrected after the study has been completed. This is why the study design…