Chest
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Retraction Of Publication
Clinical and Genetic Spectrum of Children with Primary Ciliary Dyskinesia in China.
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Cross-sectional studies are observational studies that analyze data from a population at a single point in time. They are often used to measure the prevalence of health outcomes, understand determinants of health, and describe features of a population. Unlike other types of observational studies, cross-sectional studies do not follow individuals up over time. ⋯ They are useful for establishing preliminary evidence in planning a future advanced study. This article reviews the essential characteristics, describes strengths and weaknesses, discusses methodological issues, and gives our recommendations on design and statistical analysis for cross-sectional studies in pulmonary and critical care medicine. A list of considerations for reviewers is also provided.
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Mortality has long been used as a primary end point for randomized controlled trials in critical care. Recently, a plurality of trials targeting mortality end points as their primary outcome has failed to detect a difference between study arms. ⋯ We explore some of the reasons why such trials may be biased toward a neutral result, as well as reasons to consider alternative end points that are better coupled to the expected therapeutic effect. We also discuss to what extent mortality as a binary outcome is patient-important in the ICU.
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Sample size determination is an essential step in planning a clinical study. It is critical to understand that different study designs need different methods of sample size estimation. Although there is a vast literature discussing sample size estimation, incorrect or improper formulas continue to be applied. ⋯ To assist clinical researchers in performing sample size calculations, we have developed an online calculator for common clinical study designs. The calculator is available at http://riskcalc.org:3838/samplesize/. Finally, we offer our recommendations on reporting sample size determination in clinical studies.