A simple two-stage design for quantitative responses with application to a study in diabetic neuropathic pain

Two-stage designs offer substantial advantages for early phase II studies. The interim analysis following the first stage allows the study to be stopped for futility, or more positively, it might lead to early progression to the trials needed for late phase II and phase III. If the study is to continue to its second stage, then there is an opportunity for a revision of the total sample size. Two-stage designs have been implemented widely in oncology studies in which there is a single treatment arm and patient responses are binary. In this paper the case of two-arm comparative studies in which responses are quantitative is considered. This setting is common in therapeutic areas other than oncology. It will be assumed that observations are normally distributed, but that there is some doubt concerning their standard deviation, motivating the need for sample size review. The work reported has been motivated by a study in diabetic neuropathic pain, and the development of the design for that trial is described in detail.     

Missing item imputation for quality-of-life instruments with application to asthma quality-of-life questionnaires

There has been increasing use of quality-of-life (QoL) instruments in drug development. Missing item values often occur in QoL data. A common approach to solve this problem is to impute the missing values before scoring. Several imputation procedures, such as imputing with the most correlated item and imputing with a row/column model or an item response model, have been proposed. We examine these procedures using data from two clinical trials, in which the original asthma quality-of-life questionnaire (AQLQ) and the miniAQLQ were used. We propose two modifications to existing procedures: truncating the imputed values to eliminate outliers and using the proportional odds model as the item response model for imputation. We also propose a novel imputation method based on a semi-parametric beta regression so that the imputed value is always in the correct range and illustrate how this approach can easily be implemented in commonly used statistical software. To compare these approaches, we deleted 5% of item values in the data according to three different missingness mechanisms, imputed them using these approaches and compared the imputed values with the true values. Our comparison showed that the row/column-model-based imputation with truncation generally performed better, whereas our new approach had better performance under a number scenarios.     

Testing the proportional odds model for interval-censored data

This paper discusses the goodness-of-fit test for the proportional odds model for K-sample interval-censored failure time data, which frequently occur in, for example, periodic follow-up survival studies. The proportional odds model has a feature that allows the ratio of two hazard functions to be monotonic and converge to one and provides an important tool for the modeling of survival data. To test the model, a procedure is proposed, which is a generalization of the method given in Dauxois and Kirmani [Dauxois JY, Kirmani SNUA (2003) Biometrika 90:913–922]. The asymptotic distribution of the procedure is established and its properties are evaluated by simulation studies     

Management competencies required in ambulatory care settings

A study was conducted to identify the most important competencies physician executives in medical groups and other ambulatory settings will need to have in the next five years. The specific job skills, knowledge, and abilities (SKA) that physician executives will need to acquire these competencies were also explored. The Delphi techniques were used to analyze responses from two surveys from members of the American College of Medical Practice Executives. The most important competencies were grouped into 13 management domains, each with specific SKAs. "Managing health care resources to create quality and value" and "fundamentals of business and finance" were rated as the most important competencies. The most frequently rated SKA was the "ability to build and maintain credibility and trust."     

Hypothesis Testing of Hazard Ratio Parameters in Marginal Models for Multivariate Failure Time Data

Marginal hazard models for multivariate failure time data have been studied extensively in recent literature. However, standard hypothesis test statistics based on the likelihood method are not exactly appropriate for this kind of model. In this paper, extensions of the three commonly used likelihood hypothesis test statistics are discussed. Generalized Wald, generalized score and generalized likelihood ratio tests for hazard ratio parameters in a marginal hazard model for multivariate failure time data are proposed and their asymptotic distributions examined. The finite sample properties of these statistics are studied through simulations. The proposed method is applied to data from Busselton Population Health Surveys.     

Aalen's Linear Model for Sampled Risk Set Data: A Large Sample Study

Borgan and Langholz (1997) describe a method for estimating the parameter functions in Aalen's linear hazard regression model from sampled risk set data. Using a counting process formulation and the martingale central limit theorem, we provide a study of the asymptotic distributional properties of the estimator. The results are applied to study the efficiencies of the nested case-control and counter-matched designs relative to a full cohort analysis.     

《西伯利亚的萨满教》一书评介

《西伯利亚的萨满教》(Shamanism in Sibe-ria)一书,由 V·狄奥斯泽吉(Vilmos Diószegi)和 M·霍帕尔(M·Hoppál)编著,S·西蒙自俄文和匈牙利文译出,1978年布达佩斯匈牙利科学院出版,英国科利斯(Collets)出版公司发行。据这本饶有兴味的图书介绍,在欧亚大陆北部以及中亚和北美诸民族中,作为“人类和精神世界之间的占卜者、巫医和请神者”的萨满的存在是一     

苏丹的因加萨纳人

因加萨纳人(或称塔比塔人)是苏丹许多部族之一,约有三万人,居住在苏丹东南与埃塞俄比亚相邻的青尼罗省北纬10°—12°的地方。因加萨纳人昔日曾是勇敢的武士,今天仍是其主权、尊严、习俗以及独特生活方式的忠诚捍卫者。起源因加萨纳人几乎是一个没有历史的民族。包括他们自己在内没有人知道他们     

Opportunities for woman-initiated HIV prevention methods among female sex workers in southern China

Rapid changes in China over the past two decades have led to significant problems associated with population migration and changing social attitudes, including a growing sex industry and concurrent increases in STIs and HIV. This article reports results of an exploratory study of microbicide acceptability and readiness and current HIV prevention efforts among female sex workers in two rural and one urban town in Hainan and Guangxi Provinces in southern China. The study focused on these women's knowledge and cultural understandings of options for protecting themselves from exposure to STIs and HIV, and the potential viability and acceptability of woman-initiated prevention methods. We report on ethnographic elicitation interviews conducted with women working within informal sex-work establishments (hotels, massage and beauty parlors, roadside restaurants, boarding houses). We discuss implications of these findings for further promotion of woman-initiated prevention methods such as microbicides and female condoms among female sex workers in China.     

Contraceptive use patterns within females' first sexual relationships: the role of relationships, partners, and methods

This study used the 1995 National Survey of Family Growth (NSFG) to assess whether characteristics of females' sexual partners, relationships, and choice of contraceptive methods were associated with contraceptive use patterns within their first sexual relationship. White, black, and Hispanic females under age 25 (N=915) provided retrospective information on sexual activity and contraceptive use for first sexual relationships that occurred between 1991 and 1995. Females with older sexual partners and with same race/ethnicity partners (among Hispanics) had reduced odds of ever using contraception and/or uninterrupted use. Longer sexual relationships were associated with higher odds of ever using contraception but lower odds of uninterrupted use. Females who were older at first sex, who used hormonal methods (among whites), or who switched to more effective methods during their first sexual relationships had higher odds of ever using contraception and/or uninterrupted use. In contrast, switching to less effective methods during a first sexual relationship was associated with reduced odds of uninterrupted use.