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1.
Improved two‐stage group sequential procedures for testing a secondary endpoint after the primary endpoint achieves significance 下载免费PDF全文
Huiling Li Jianming Wang Xiaolong Luo Janis Grechko Christopher Jennison 《Biometrical journal. Biometrische Zeitschrift》2018,60(5):893-902
In two‐stage group sequential trials with a primary and a secondary endpoint, the overall type I error rate for the primary endpoint is often controlled by an α‐level boundary, such as an O'Brien‐Fleming or Pocock boundary. Following a hierarchical testing sequence, the secondary endpoint is tested only if the primary endpoint achieves statistical significance either at an interim analysis or at the final analysis. To control the type I error rate for the secondary endpoint, this is tested using a Bonferroni procedure or any α‐level group sequential method. In comparison with marginal testing, there is an overall power loss for the test of the secondary endpoint since a claim of a positive result depends on the significance of the primary endpoint in the hierarchical testing sequence. We propose two group sequential testing procedures with improved secondary power: the improved Bonferroni procedure and the improved Pocock procedure. The proposed procedures use the correlation between the interim and final statistics for the secondary endpoint while applying graphical approaches to transfer the significance level from the primary endpoint to the secondary endpoint. The procedures control the familywise error rate (FWER) strongly by construction and this is confirmed via simulation. We also compare the proposed procedures with other commonly used group sequential procedures in terms of control of the FWER and the power of rejecting the secondary hypothesis. An example is provided to illustrate the procedures. 相似文献
2.
Taewoo Kim Charlotte Haney Janis Faye Hutchinson 《Culture, medicine and psychiatry》2012,36(4):621-639
Based on fieldwork with a highly uninsured and underinsured Korean American population, this article maps how the current healthcare system in the United States disenfranchises those of marginal insurance status. The vulnerability of these disenfranchised biological citizens is multiplied through exposure to disproportional health risks compounded by exclusion from essential healthcare. The first-generation Korean Americans, who commonly work in small businesses, face the double burden of increased health risks from long, stress-laden work hours and lack of access to healthcare due to the prohibitive costs of health insurance for small business owners. Even as their health needs become critical, their insurance status and costly medical bills discourage them from visiting healthcare institutions, leaving Korean Americans outside the ??political economy of hope?? (Good, Cult Med Psychiatry 52:61?C69, 2001). Through an ethnographic examination of the daily practice of doing-without-health among a marginalized sub-group in American society, this paper articulates how disenfranchised biological citizenship goes beyond creating institutional barriers to healthcare to shaping subjectivities of the disenfranchised. 相似文献
3.
Achim Hoerauf Rolf D. Walter Hans Remme Janis Lazdins Bernhard Fleischer 《Trends in parasitology》2001,17(12):860-567
The Bernhard Nocht Institute for Tropical Medicine and the UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases held an international conference to review recent achievements in research and control of onchocerciasis and lymphatic filariasis on 19-23 September 2001 in Hamburg, Germany. 相似文献
4.
Since it was first detected in 1999, West Nile virus (WNV) quickly spread, becoming the dominant vector-borne disease in North
America. Sometimes fatal to humans, WNV is even more widespread among birds, with hundreds of species known to be susceptible
to WNV infection in North America alone. However, despite considerable mortality and local declines observed in American crows
(Corvus brachyrhynchos), there has been little evidence of a large regional association between WNV susceptibility and population declines of any
species. Here we demonstrate a correlation between susceptibility to WNV measured by large-scale testing of dead birds and
two indices of overall population change among bird species following the spread of WNV throughout California. This result
was due primarily to declines in four species of Corvidae, including all species in this family except common ravens (Corvus corax). Our results support the hypothesis that susceptibility to WNV may have negative population consequences to most corvids on
regional levels. They also provide confirmation that dead animal surveillance programs can provide important data indicating
populations most likely to suffer detrimental impacts due to WNV. 相似文献
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6.
Dyscalculia, dyslexia, and specific language impairment (SLI) are relatively specific developmental learning disabilities in math, reading, and oral language, respectively, that occur in the context of average intellectual capacity and adequate environmental opportunities. Past research has been dominated by studies focused on single impairments despite the widespread recognition that overlapping and comorbid deficits are common. The present study took an epidemiological approach to study the learning profiles of a large school age sample in language, reading, and math. Both general learning profiles reflecting good or poor performance across measures and specific learning profiles involving either weak language, weak reading, weak math, or weak math and reading were observed. These latter four profiles characterized 70% of children with some evidence of a learning disability. Low scores in phonological short-term memory characterized clusters with a language-based weakness whereas low or variable phonological awareness was associated with the reading (but not language-based) weaknesses. The low math only group did not show these phonological deficits. These findings may suggest different etiologies for language-based deficits in language, reading, and math, reading-related impairments in reading and math, and isolated math disabilities. 相似文献
7.
Carolyn O. Walsh Cara B. Ebbeling Janis F. Swain Robert L. Markowitz Henry A. Feldman David S. Ludwig 《PloS one》2013,8(3)
Background
The major circulating metabolic fuels regulate hunger, and each is affected by dietary composition. An integrated measure of postprandial energy availability from circulating metabolic fuels may help inform dietary recommendations for weight maintenance after weight loss.Aim
We examined the effect of low-fat (LF, 60% of energy from carbohydrate, 20% fat, 20% protein), low-glycemic index (LGI, 40%–40%-20%), and very low-carbohydrate (VLC, 10%–60%-30%) diets on total postprandial metabolic fuel energy availability (EA) during weight loss maintenance.Methods
Eight obese young adults were fed a standard hypocaloric diet to produce 10–15% weight loss. They were then provided isocaloric LF, LGI, and VLC diets in a randomized crossover design, each for a 4-week period of weight loss maintenance. At the end of each dietary period, a test meal representing the respective diet was provided, and blood samples were obtained every 30 minutes for 5 hours. The primary outcome was EA, defined as the combined energy density (circulating level×relative energy content) of glucose, free fatty acids, and β-hydroxybutyrate. Secondary outcomes were individual metabolic fuels, metabolic rate, insulin, glucagon, cortisol, epinephrine, and hunger ratings. Respiratory quotient was a process measure. Data were analyzed by repeated-measures analysis of variance, with outcomes compared in the early (30 to 150 min) and late (180 to 300 min) postprandial periods.Results
EA did not differ between the test meals during the early postprandial period (p = 0.99). However, EA in the late postprandial period was significantly lower after the LF test meal than the LGI (p<0.0001) and VLC (p<0.0001) test meals. Metabolic rate also differed in the late postprandial period (p = 0.0074), with higher values on the VLC than LF (p = 0.0064) and LGI (p = 0.0066) diets.Conclusion
These findings suggest that an LF diet may adversely affect postprandial EA and risk for weight regain during weight loss maintenance.Trial Registration
ClinicalTrials.gov NCT00315354相似文献8.
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10.
BAY K 8644, a 1,4-Dihydropyridine Ca2+ Channel Activator: Dissociation of Binding and Functional Effects in Brain Synaptosomes 总被引:6,自引:0,他引:6
K+-stimulated 45Ca2+ uptake into rat brain and guinea pig cerebral cortex synaptosomes was measured at 10 s and 90 s at K+ concentrations of 5-75 mM. Net increases in 45Ca2+ uptake were observed in rat and guinea pig brain synaptosomes. 45Ca2+ uptake under resting or depolarizing conditions was not increased by the 1,4-dihydropyridine BAY K 8644, which has been shown to activate Ca2+ channels in smooth and cardiac muscle. High-affinity [3H]nitrendipine binding in guinea pig synaptosomes (KD = 1.2 X 10(-10) M, Bmax = 0.56 pmol mg-1 protein) was competitively displaced with high affinity (IC50 2.3 X 10(-9) M) by BAY K 8644. Thus high-affinity Ca2+ channel antagonist and activator binding sites exist in synaptosome preparations, but their relationship to functional Ca2+ channels is not clear. 相似文献