What is the evidence status of Appropriate Use Criteria (AUC)? Insight from a matching exercise with the guidelines for echocardiography

There is interest in adapting the American Appropriate Use Criteria (AUC) for transthoracic echocardiography to Australian practice. We matched 90 of 98 AUC with the guidelines (53 appropriate, 12 sometimes appropriate, 25 rarely appropriate), but eight lacked any match. Among the matched criteria, 76 (82%) indications were concordant with the guidelines. A stronger evidence base would be desirable to settle these discrepancies before Australian adoption of AUC.     

血管重建术后冠心病相关证型辨证标准的研究

目的通过专家问卷调查,总结血管重建术后冠心病患者中医证候分布规律,建立辨证标准,分析其实用性和可行性。方法根据以往研究结果,制订专家咨询问卷,对全国17个省市45家医院的105位相关专家进行问卷调查,建立Epidata3.1数据库,采用SPSS13.0对数据进行统计分析,总结血管重建术后冠心病患者的常见证型,并建立辨证标准,分析其实用性和可行性。结果本次调查共发放专家问卷105份,回收105份,回收率为100%,其中103份问卷有效,有效率98.10%。根据证型常见度,将累积百分率≥80%且变异系数≤0.45者作为血管重建术后的主要证型(血瘀证、气虚证、痰浊证);将累积百分率≥80%且变异系数≤0.45者的症状作为支持该证型诊断的要素;以百分比反映专家对该问卷的认可度。结论通过对103名心血管病专业中医专家的经验总结,为血管重建术后主要证型的辨证标准提供了依据。     

Monotonic Tension-Torsion Experiments and FE Modeling on Notched Specimens Produced by SLM Technology from SS316L

The aim of this work was to monitor the mechanical behavior of 316L stainless steel produced by 3D printing in the vertical direction. The material was tested in the “as printed” state. Digital Image Correlation measurements were used for 4 types of notched specimens. The behavior of these specimens under monotonic loading was investigated in two loading paths: tension and torsion. Based on the experimental data, two yield criteria were used in the finite element analyses. Von Mises criterion and Hill criterion were applied, together with the nonlinear isotropic hardening rule of Voce. Subsequently, the load-deformation responses of simulations and experiments were compared. Results of the Hill criterion show better correlation with experimental data. The numerical study shows that taking into account the difference in yield stress in the horizontal direction of printing plays a crucial role for modeling of notched geometries loaded in the vertical direction of printing. Ductility of 3D printed specimens in the “as printed” state is also compared with 3D printed machined specimens and specimens produced by conventional methods. “As printed” specimens have 2/3 lower ductility than specimens produced by a conventional production method. Machining of “as printed” specimens does not affect the yield stress, but a significant reduction of ductility was observed due to microcracks arising from the pores as a microscopic surface study showed.     

Optimal Designs in Stability Studies

New optimality criteria for stability studies are proposed, and the related optimal designs are investigated. For each optimality criterion, optimal designs are identified within a class of competing designs. The property of the optimal designs for detecting slope differences is discussed.     

Optimal flexible sample size design with robust power

It is well recognized that sample size determination is challenging because of the uncertainty on the treatment effect size. Several remedies are available in the literature. Group sequential designs start with a sample size based on a conservative (smaller) effect size and allow early stop at interim looks. Sample size re‐estimation designs start with a sample size based on an optimistic (larger) effect size and allow sample size increase if the observed effect size is smaller than planned. Different opinions favoring one type over the other exist. We propose an optimal approach using an appropriate optimality criterion to select the best design among all the candidate designs. Our results show that (1) for the same type of designs, for example, group sequential designs, there is room for significant improvement through our optimization approach; (2) optimal promising zone designs appear to have no advantages over optimal group sequential designs; and (3) optimal designs with sample size re‐estimation deliver the best adaptive performance. We conclude that to deal with the challenge of sample size determination due to effect size uncertainty, an optimal approach can help to select the best design that provides most robust power across the effect size range of interest. Copyright © 2016 John Wiley & Sons, Ltd.     

兔胸主动脉在冻结状态下的断裂方式及其断裂判据的实验探讨

采用动态力学分析仪（DMA）研究温度、降温速率以及低温保护剂对冻结状态下兔胸主动脉的断裂方式的影响,并探讨其在冻结状态下断裂判据的确定方法.研究结果表明：均以5 ℃/min降温,主动脉在20 ℃时的轴向拉伸断裂方式表现为典型的韧性断裂,而温度达到-50 ℃或-80 ℃时,其断裂方式表现为典型的脆性断裂,其抗断裂能力随着温度降低而快速减弱;分别采用20 ℃/min和5 ℃/min降温到-50 ℃时,对主动脉的断裂方式影响不大,但对其抗断裂能力稍有影响;采用10%（V/V）二甲亚砜（DMSO）作低温保护剂,其断裂方式为典型的韧性断裂,抗断裂能力显著强于未经DMSO处理的血管;血管周向的抗断裂能力明显大于轴向,这可以解释为何主动脉血管冻存过程裂纹扩展方向一般与轴向垂直的现象.     

Quasi-steady state approximation to a fungal growth model

In a previous paper, we proposed a fungal growth model (Lamouret al., 2001 IMA J. Math. Appl. Med. Biol., 17, 329–346),describing the colonization and decomposition of substrate,subsequent uptake of nutrients, and incorporation into fungalbiomass, and performed an overall-steady-state analysis. Inthis paper we assume that where nutrient dynamics are much fasterthan the dynamics of fungal biomass and substrate, the systemwill reach a quasi-steady-state relatively quickly. We showhow the quasi-steady-state approximation is a simplificationof the full fungal growth model. We then derive an explicitfungal invasion criterion, which was not possible for the fullmodel, and characterize parameter domains for invasion and extinction.Importantly, the fungal invasion criterion takes two forms:one for systems where carbon is limiting, another for systemswhere nitrogen is limiting. We focus attention on what happensin the short term immediately following the introduction ofa fungus to a fungal-free system by analysing the stabilityof the trivial steady state, and then check numerically whetherthe fungus is able to persist. The derived invasion criterionwas found to be valid also for the full model. Knowledge ofthe factors that determine invasion is essential to an understandingof fungal dynamics. The simplified model allows the invasioncriterion to be tested with experimental data.     

多普勒超声评分体系在晚孕胎儿监护中的应用及意义

目的评价多普勒超声评分体系(DUPS)在晚孕胎儿监护中的应用价值。方法选择459例孕龄大于32周的孕妇行彩色多普勒超声检查,检测胎儿大脑中动脉搏动指数(MCAPI)、心脏大小、心功能、脐动脉搏动指数(UmAPI)、静脉导管搏动指数(DVPI)及脐静脉血流频谱(UV)。根据上述5项指标计算其DUPS评分,无异常时每项得2分,有异常时得1分或0分。将其评分结果与其围产期结局进行比较和分析。结果459例晚孕胎儿中有402例正常分娩(87.58%),48例因临床上需要而提早终止妊娠(10.46%),9例围产期死亡(1.96%)。正常分娩、提早终止妊娠、围产期死亡组间DUPS评分有显著性差异(P<0.001)。应用受试者工作特性曲线法确定预测围产期结局不良(包括提早终止妊娠和围产期死亡)DUPS评分的最佳诊断界点为8分(灵敏度78.95%,特异度95.52%),预测围产期死亡DUPS评分的最佳诊断界点为6分(灵敏度100.00%,特异度99.11%)。结论DUPS在预测晚孕胎儿的围产期结局不良中具有重要的临床价值,值得进一步研究与应用。     

Fridge: Focused fine‐tuning of ridge regression for personalized predictions

Statistical prediction methods typically require some form of fine‐tuning of tuning parameter(s), with K‐fold cross‐validation as the canonical procedure. For ridge regression, there exist numerous procedures, but common for all, including cross‐validation, is that one single parameter is chosen for all future predictions. We propose instead to calculate a unique tuning parameter for each individual for which we wish to predict an outcome. This generates an individualized prediction by focusing on the vector of covariates of a specific individual. The focused ridge—fridge—procedure is introduced with a 2‐part contribution: First we define an oracle tuning parameter minimizing the mean squared prediction error of a specific covariate vector, and then we propose to estimate this tuning parameter by using plug‐in estimates of the regression coefficients and error variance parameter. The procedure is extended to logistic ridge regression by using parametric bootstrap. For high‐dimensional data, we propose to use ridge regression with cross‐validation as the plug‐in estimate, and simulations show that fridge gives smaller average prediction error than ridge with cross‐validation for both simulated and real data. We illustrate the new concept for both linear and logistic regression models in 2 applications of personalized medicine: predicting individual risk and treatment response based on gene expression data. The method is implemented in the R package fridge.