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.     

Dependence Estimation Over a Finite Bivariate Failure Time Region

This articleconcerns nonparametric estimation of association between bivariatefailure times. In the presence of independent right censoring,the support for failure time variates may be restricted and measuresof dependence over a finite failure time region may be of particularinterest. To this end, the reciprocal cross ratio function, weightedby the bivariate failure time density, is proposed as a summarymeasure of dependence over a failure time region. This `relativerisk' estimator is shown to be consistent and asymptoticallynormally distributed, with consistent bootstrap variance estimator.A finite-region version of Kendall's tau, which is suitable forcensored failure time data, is also proposed, and correspondingasymptotic distribution theory is noted. The accuracy of theseasymptotic approximations is studied in simulations and an illustrationis provided.     

Nonparametric Tests for Stratum Effects in the Cox Model

Thispaper considers the stratified proportional hazards model witha focus on the assessment of stratum effects. The assessmentof such effects is often of interest, for example, in clinicaltrials. In this case, two relevant tests are the test of stratuminteraction with covariates and the test of stratum interactionwith baseline hazard functions. For the test of stratum interactionwith covariates, one can use the partial likelihood method (Kalbfleischand Prentice, 1980; Lin, 1994). For the test of stratum interactionwith baseline hazard functions, however, there seems to be noformal test available. We consider this problem and propose aclass of nonparametric tests. The asymptotic distributions ofthe tests are derived using the martingale theory. The proposedtests can also be used for survival comparisons which need tobe adjusted for covariate effects. The method is illustratedwith data from a lung cancer clinical trial.     

《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.     

Effects of a single-lesson tobacco prevention curriculum on knowledge, skill identification and smoking intention

One in five students report experimenting with tobacco before the age of 13 and most prevention efforts take place in the school setting. This study measures the effect of a single-lesson tobacco prevention curriculum, conducted by a health education center, focusing on knowledge of tobacco, ability to identify refusal techniques, and intent not to smoke. Data were collected, via electronic keypads, from students visiting a non-school, health education center in Michigan (n = 704 intervention and 85 comparison). Contingency table Chi-squared tests and t-tests demonstrated that a single lesson can improve general knowledge and ability to identify appropriate refusal techniques. Improvement in intent not to smoke was not significant because both groups had very high intent prior to implementation. Similar to results from other programs, multivariate logistic regression of gender, general knowledge, and skill identification revealed that only the skill variable was associated with intent not to smoke at pretest. Recommendations are given for further research and for designing more effective curricula or programs.     

Characteristics of children in residential treatment in New York State

This study addresses three questions about the population of children and families served in the highest level of care in the child welfare system in New York State residential treatment centers (RTCs): (1) How prevalent are emotional and behavioral problems in the youth entering RTCs? (2) Has the proportion of youth with such problems increased compared to 10 years ago? (3) Are there identifiable subgroups of youth entering RTCs? One-fourth of RTC admissions in fiscal year 2001 were randomly selected from a representative sample of 16 RTCs. The study completed a standardized data collection instrument based on a review of agency records, and included information that was known at the time each child was admitted. The results show significant increases compared to t10 years earlier in the proportion of youth with mental health problems and juvenile justice backgrounds. The findings suggest that youth who traditionally have been served by other systems of care are now being served in the child welfare system. The increased treatment needs of these youth and the heterogeneity of the RTC population have important implications for policies, programs, and practice.