Comparing clinical data with administrative data for producing acute myocardial infarction report cards

Summary.  We compared measures of hospital performance by using both administrative and clinical data sources. Hospital-specific mortality outcomes on 10086 patients who had been admitted to 102 hospitals with a diagnosis of acute myocardial infarction in Ontario, Canada, were used as a test-case. Four and six hospitals were identified as having mortality that was statistically significantly higher than expected by using administrative and clinical data respectively, when model-based indirect standardization was used. When using random-effects models, zero and two hospitals were identified as having significantly higher mortality by using administrative and clinical data respectively. Approximately one in four hospitals changed at least two decile rankings when clinical data were used compared with when administrative data were used.     

从MtDNA研究角度看新疆地区古代居民遗传结构的变化

本文对新疆吐鲁番盆地以及罗布诺尔地区青铜———早期铁器时代古代居民的MtDNA进行了研究,使用4对套叠引物对线粒体基因组的调控区(313bp)进行扩增和测序,从31例古代个体中得到了30个DNA序列。系统发育分析实验结果表明:至少在汉代以前,欧洲和东亚谱系在新疆境内存在反向渗入,相比之下,亚洲序列向西的渗入比较零碎,不如欧洲谱系成分的东进活跃。在此之后,随着东亚群体向西迁徙的增加,欧洲谱系的影响出现弱化的趋势。     

Statistical Genetics and Genetical Statistics: a Forensic Perspective*

This review paper focuses on forensic aspects of the relation between statistics and genetics. Some of the scientific achievements of the Swedish psychiatrist and geneticist Erik Essen‐Möller may be viewed in the above interdisciplinary context. In a number of situations the correct familial relation between a group of individuals is required. We discuss recent work done to relax some assumptions involved in the classical calculations in 10 ). Moreover, we extend the discussion to identification problems. In a given case there may be a large number of possible family constellations or pedigrees. A prior probability distribution is established. The posterior model accounts for the combinatorial complexities of the pedigrees, mutations, kinship, and uncertainty in allele frequencies. Examples are based on the shareware program FAMILIAS, see http://www.nr.no/familias . A main message of the present paper is that the Bayesian approach is a convenient framework to down‐weight unreasonable (e.g. incestuous) pedigrees that may always appear likely if only DNA‐measurements are used.     

两种动物基因组DNA提取方法的比较

分别用酚抽提法和盐洗法提取鼠、鲤、鲍三种动物基因组DNA,利用分光光度计测定其OD260与OD280的吸光值,计算比率估计核酸的纯度,并利用琼脂糖凝胶电泳观察DNA片段在凝胶中的位置,鉴定DNA.最终确定了一种简便、快捷、经济并适用于大多数动物基因组DNA提取的方法.     

原位杂交中鲑鱼精DNA处理方法探究

采用机械打断/沸水浴和超声波处理两种方法对原位杂交中的封闭DNA——鲑鱼精DNA进行了断裂处理。分别探讨了不同的吹打次数、煮沸时间和超声波处理时间对鲑鱼精DNA片段大小的影响,并且对机械打断/沸水浴和超声波处理两种方法结果进行了比较分析。研究结果表明在煮沸时间20min时,吹打次数可根据所需原位杂交片段大小进行调整;超声波适宜打断时间为20min。     

汲取·改造·升华──《药》、《作粗活的人和不作粗活的人》、《绳子》比较

《药》与《作粗活的人和不作粗活的人》歌颂了革命者大义凛然的牺牲精神，揭示了群众对革命的不理解和革命者脱离群众的错误倾向。在艺术方面，两首散文诗具有精湛的艺术构思，并采用侧面描写手法和双线结构方式。《作粗活的人和不作粗活的人》和《绳子》又有血缘关系。可见，世界各国文学是互相影响、血脉相连的。     

Uncertainties in the CIIT Model for Formaldehyde-Induced Carcinogenicity in the Rat: A Limited Sensitivity Analysis–I

Scientists at the CIIT Centers for Health Research (Conolly et al., 2000, 2003; Kimbell et al., 2001a, 2001b) developed a two-stage clonal expansion model of formaldehyde-induced nasal cancers in the F344 rat that made extensive use of mechanistic information. An inference of their modeling approach was that formaldehyde-induced tumorigenicity could be optimally explained without the role of formaldehyde's mutagenic action. In this article, we examine the strength of this result and modify select features to examine the sensitivity of the predicted dose response to select assumptions. We implement solutions to the two-stage cancer model that are valid for nonhomogeneous models (i.e., models with time-dependent parameters), thus accounting for time dependence in variables. In this reimplementation, we examine the sensitivity of model predictions to pooling historical and concurrent control data, and to lumping sacrificed animals in which tumors were discovered incidentally with those in which death was caused by the tumors. We found the CIIT model results were not significantly altered with the nonhomogeneous solutions. Dose-response predictions below the range of exposures where tumors occurred in the bioassays were highly sensitive to the choice of control data. In the range of exposures where tumors were observed, the model attributed up to 74% of the added tumor probability to formaldehyde's mutagenic action when our reanalysis restricted the use of the National Toxicology Program (NTP) historical control data to only those obtained from inhalation exposures. Model results were insensitive to hourly or daily temporal variations in DNA protein cross-link (DPX) concentration, a surrogate for the dose-metric linked to formaldehyde-induced mutations, prompting us to utilize weekly averages for this quantity. Various other biological and mathematical uncertainties in the model have been retained unmodified in this analysis. These include model specification of initiated cell division and death rates, and uncertainty and variability in the dose response for cell replication rates, issues that will be considered in a future paper.     

Interpreting forensic DNA mixtures: allowing for uncertainty in population substructure and dependence

We consider the assessment of deoxyribonucleic acid (DNA) profiles from biological samples containing a mixture of DNA from more than one person. The problem has been investigated in the context of likelihood ratios by Weir and co-workers under the assumption of independent alleles in DNA profiles. However, uncertainty about independence may arise from various factors such as population substructure and relatedness. This issue has received considerable attention in recent years. Ignoring this uncertainty may seriously overstate the strength of the evidence and therefore disadvantage innocent suspects. Taking this uncertainty into account, we develop a general formula for calculating the match probabilities of DNA profiles. Thus, we extend the result derived by Weir and co-workers to the dependence situation, which is often more to the benefit of the defendant in comparison with the simple product rule result based on an independence assumption. The effect of dependence of alleles on likelihood ratio estimates can be seen in the analysis of two real data sets.     

A new hybrid estimation method for the generalized pareto distribution

ABSTRACT

The generalized Pareto distribution (GPD) is important in the analysis of extreme values, especially in modeling exceedances over thresholds. Most of the existing methods for estimating the scale and shape parameters of the GPD suffer from theoretical and/or computational problems. A new hybrid estimation method is proposed in this article, which minimizes a goodness-of-fit measure and incorporates some useful likelihood information. Compared with the maximum likelihood method and other leading methods, our new hybrid estimation method retains high efficiency, reduces the estimation bias, and is computation friendly.     

The Identification of “Unusual” Health-Care Providers From a Hierarchical Model

It has become common to adopt a hierarchical model structure when comparing the performance of multiple health-care providers. This structure allows some variation in such measures, beyond that explained by sampling variation, to be “normal,” in recognition of the fact that risk-adjustment is never perfect. The shrinkage estimates arising from such a model structure also have appealing properties.

It is not immediately clear, however, how “unusual” providers, that is, any with particularly high or low rates, can be identified based on such a model. Given that some variation in underlying rates is assumed to be the norm, we argue that it is not generally appropriate to identify a provider as interesting based only on evidence of it lying above or below the population mean. We note with concern, however, that this practice is not uncommon.

We examine in detail three possible strategies for identifying unusual providers, carefully distinguishing between statistical “outliers” and “extremes.” A two-level normal model is used for mathematical simplicity, but we note that much of the discussion also applies to alternative data structures. Further, we emphasize throughout that each approach can be viewed as resulting from a Bayesian or a classical perspective. Three worked examples provide additional insight.