Stepped‐wedge cluster randomised controlled trials: a generic framework including parallel and multiple‐level designs

Stepped‐wedge cluster randomised trials (SW‐CRTs) are being used with increasing frequency in health service evaluation. Conventionally, these studies are cross‐sectional in design with equally spaced steps, with an equal number of clusters randomised at each step and data collected at each and every step. Here we introduce several variations on this design and consider implications for power. One modification we consider is the incomplete cross‐sectional SW‐CRT, where the number of clusters varies at each step or where at some steps, for example, implementation or transition periods, data are not collected. We show that the parallel CRT with staggered but balanced randomisation can be considered a special case of the incomplete SW‐CRT. As too can the parallel CRT with baseline measures. And we extend these designs to allow for multiple layers of clustering, for example, wards within a hospital. Building on results for complete designs, power and detectable difference are derived using a Wald test and obtaining the variance–covariance matrix of the treatment effect assuming a generalised linear mixed model. These variations are illustrated by several real examples. We recommend that whilst the impact of transition periods on power is likely to be small, where they are a feature of the design they should be incorporated. We also show examples in which the power of a SW‐CRT increases as the intra‐cluster correlation (ICC) increases and demonstrate that the impact of the ICC is likely to be smaller in a SW‐CRT compared with a parallel CRT, especially where there are multiple levels of clustering. Finally, through this unified framework, the efficiency of the SW‐CRT and the parallel CRT can be compared. © 2014 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd.     

脑功能磁共振图像中Nyquist伪影的处理方法研究

Nyquist伪影是功能磁共振成像过程中产生的一种特有的伪影,使图像信噪比下降,并对图像的可视化及功能定位产生不利影响.尽可能地消除Nyquist伪影,无论对于改善图像的视觉效果,还是对后续的功能定位分析和可视化都具有重要意义.目前对Nyquist伪影还没有有效的处理方法.本文根据功能磁共振图像本身的信息,首次提出一种基于模糊聚类技术的Nyquist伪影的处理方法,能比较有效地消除Nyquist伪影.     

Statistical detection of geographic clusters of resistant Escherichia coli in a regional network with WHONET and SaTScan

Background: While antimicrobial resistance threatens the prevention, treatment, and control of infectious diseases, systematic analysis of routine microbiology laboratory test results worldwide can alert new threats and promote timely response. This study explores statistical algorithms for recognizing geographic clustering of multi-resistant microbes within a healthcare network and monitoring the dissemination of new strains over time.

Methods: Escherichia coli antimicrobial susceptibility data from a three-year period stored in WHONET were analyzed across ten facilities in a healthcare network utilizing SaTScan’s spatial multinomial model with two models for defining geographic proximity. We explored geographic clustering of multi-resistance phenotypes within the network and changes in clustering over time.

Results: Geographic clustering identified from both latitude/longitude and non-parametric facility groupings geographic models were similar, while the latter was offers greater flexibility and generalizability. Iterative application of the clustering algorithms suggested the possible recognition of the initial appearance of invasive E. coli ST131 in the clinical database of a single hospital and subsequent dissemination to others.

Conclusion: Systematic analysis of routine antimicrobial resistance susceptibility test results supports the recognition of geographic clustering of microbial phenotypic subpopulations with WHONET and SaTScan, and iterative application of these algorithms can detect the initial appearance in and dissemination across a region prompting early investigation, response, and containment measures.     

2013—2017年上海市金山区新登记肺结核患者时空聚集性分析

目的 分析2013—2017年上海市金山区活动性肺结核疫情的时空分布特征,探寻肺结核疫情防治重点区域。方法 通过国家《结核病管理信息系统》收集金山区肺结核患者基本信息,以街镇为单位(共计11个),用SaTScan 9.6软件对上海市金山区2013—2017年新登记肺结核患者登记率进行时空分析,通过ArcGIS 10.4软件对结果进行可视化呈现。结果 金山区2013—2017年新登记活动性肺结核患者1021例,年均登记率为25.64/10万(1021/3981892),其中户籍人口和非户籍人口肺结核患者年均登记率分别为28.68/10万(757/2639117)和19.66/10万(264/1342775)。空间分布上总体肺结核患者登记率最高的街镇在张堰镇,户籍人口登记的肺结核患者主要分布在张堰镇、漕泾镇、金山工业区;非户籍人口主要分布在廊下镇和石化街道。单纯时间扫描结果显示,总体与户籍人口登记肺结核患者的聚集时间均为2014—2015年;单纯空间扫描结果显示,总体登记肺结核患者的聚集区为张堰镇,而户籍人口聚集区为金山区东北部四街镇(亭林镇、漕泾镇、张堰镇和工业区);时空扫描显示,金山区总体人口[相对风险值(RR)=1.50,对数似然比(LLR)=10.35,P<0.01]和户籍人口(RR=1.72,LLR=13.29,P<0.01)肺结核一级聚集区均在2014—2015年出现,聚集区域均为亭林镇、漕泾镇、张堰镇、工业区。结论 金山区肺结核发病具有一定的时空聚集性,聚集性主要受户籍人口影响,东北部四街镇为金山区肺结核高发区域。     

The role of insulin in clustering of serum lipids and blood pressure in children and adolescents

Summary In adults hyperinsulinaemia is associated with an atherogenic risk profile including obesity, low levels of HDL-cholesterol, high levels of triglycerides and elevated blood pressure. To examine these associations in the young we studied the cross-sectional relationships of insulin with obesity indices (body mass index, subscapular skinfold thickness), serum lipids and blood pressure in 1,865 children, adolescents and young adults aged 6–24 years. We also used longitudinal data to study the value of a single insulin measurement to predict high risk factor levels and clustering of multiple risk factors after a 6-year follow-up. In cross-sectional analyses the levels of triglycerides, HDL-cholesterol, systolic blood pressure and obesity indices were usually significantly different across the quartiles of fasting insulin in both sexes among children, adolescents and young adults. In general, no associations were seen with total cholesterol or LDL-cholesterol. In prospective analysis elevated baseline insulin was related to the incidence of hypertriglyceridaemia (95th percentile) at the follow-up. This relationship persisted even after adjustments for baseline obesity or 6-year change in obesity status. Moreover, baseline insulin concentration was higher in subjects who subsequently showed clustering of high triglycerides, low HDL-cholesterol and high systolic blood pressure levels at the follow-up. We conclude that high fasting insulin levels measured in children and adolescents predict the development of hypertriglyceridaemia years later. In addition, high insulin levels seem to precede the development of a potentially atherogenic risk factor profile including low HDL-cholesterol, high triglycerides and high systolic blood pressure.Abbreviations SBP Systolic blood pressure - DBP diastolic blood pressure - BMI body mass index     

喀什地区内脏利什曼病分布的时间-空间聚集性研究

目的 探讨喀什地区内脏利什曼病分布的时间-空间聚集性.方法 以地理信息系统为依据,运用时空统计软件的Poisson模型对喀什地区既往11年内脏利什曼病发病数据进行分析,结合地理方位及遥感图片确定聚集区.结果 喀什地区存在3个内脏利什曼病分布的高危聚集区及其对应的高发时间框.A聚集区(中心经纬度:E 76.08°,N 39.52°)半径为6.58 km,在1999年1月1日至2003年12月31日的时间框内,聚集区内内脏利什曼病的累积发病率是周围地区的45.98倍(P＜0.0001);B聚集区(中心经纬度:E 79.20°,N 39.91°)半径为4.93 km,在2002年1月1日至2006年12月31日的时间框内,聚集区内内脏利什曼病的累积发病率是周围地区的9.58倍(P＜0.0001);C聚集区(中心经纬度:E76.23°,N39.40°)半径为7.63 km,在2000年1月1日至2004年12月31日的时间框内,聚集区内内脏利什曼病的累积发病率是周围地区的5.18倍(P＜0.0001).结论 喀什地区内脏利什曼病的发病为非随机分布,存在明显的时间-空间聚集性,3个高危聚集区均位于绿洲地区.     

Common predictor effects for multivariate longitudinal data

Multivariate outcomes measured longitudinally over time are common in medicine, public health, psychology and sociology. The typical (saturated) longitudinal multivariate regression model has a separate set of regression coefficients for each outcome. However, multivariate outcomes are often quite similar and many outcomes can be expected to respond similarly to changes in covariate values. Given a set of outcomes likely to share common covariate effects, we propose the clustered outcome common predictor effect model and offer a two step iterative algorithm to fit the model using available software for univariate longitudinal data. Outcomes that share predictor effects need not be chosen a priori; we propose model selection tools to let the data select outcome clusters. We apply the proposed methods to psychometric data from adolescent children of HIV+ parents. Copyright © 2009 John Wiley & Sons, Ltd.     

A Study of Smoking Disparity and Factors Associated With Children Smoking Behavior in the Mountain and City Schools in Taiwan

BACKGROUND:  While higher smoking prevalences have been better described for adults and adolescents in the mountainous areas than in the plain area in Taiwan, no studies have previously examined whether this disparity begins with children in elementary schools. The purpose of this study was thus designed to explore clustering in smoking behavior among elementary school children attending mountain schools compared to those attending city schools.
METHODS:  This study analyzed data obtained by a survey on smoking behavior collected during the School Smoking Survey Project performed in 13 elementary schools of Taoyuan County, Taiwan. Overall, 1585 third and fourth graders (mean age 8.9 years) participated in the study. A multilevel logistic regression analysis was performed to explore the effects of school location on individual smoking behavior among elementary school children while controlling for individual-level characteristics.
RESULTS:  Overall, 34.9% of the elementary school students in the mountain schools reported having tried cigarette smoking compared to only 9.6% of students from city schools. Students attending mountain schools had a greater likelihood of reporting smoking than students attending city schools after controlling for individual-level characteristics (OR = 2.57, 95% CI = 1.10-5.99).
CONCLUSIONS:  A significant individual clustering in smoking behavior was found among third- and fourth-grade children attending mountain schools. The new findings suggest that the adult geographic smoking disparity begins in elementary school. Interventions aimed at reducing smoking disparity in adults need to target elementary schools in high-risk locations.