ISSN:0277-6715    

DOI:10.1002/sim.4780142402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:0277-6715    

DOI:10.1002/sim.4780142403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe internal validity of the recording of information about ischaemic heart disease (IHD) and chronic obstructive pulmonary disease (COPD) in the administrative health care datafiles of the Canadian province of Saskatchewan is investigated. Comparisons between hospital data and medical charts for acute myocardial infarction and chronic airways obstruction patients showed excellent diagnostic agreement: 97 per cent and 94 per cent, respectively. Appropriate physician service claims were identified for 89 per cent of hospitalizations for IHD and COPD and exact concordance between diagnoses in the two datafiles varied between 15 per cent for acute/sub‐acute IHD and 80 per cent for asthma; including any physician diagnosis within the same broad category (IHD or COPD) increased concordance to 79–94 per cent for IHD and 64–88 per cent for COPD. Contextual information related to the hospitalizations was clinically and epidemiologically real

ISSN:0277-6715    

DOI:10.1002/sim.4780142404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA procedure for identifying subgroups that are homogeneous with respect to an outcome variable is described. The method, search partition analysis (SPAN), is formulated in terms of a numeric outcome variableyand a set of predictors, explanatory variables or risk factorsx=x1,x2, …,xp. The objective is to split observations into two groups by a binary partition, specified using Boolean expressions of the predictors,x, such thatyis as homogeneous as possible in the resultant groups; uniformly ‘low’ in one and uniformly ‘high’ in the other. Subgroups within each of the two groups can be identified from the Boolean expressions. SPAN implements a search for the ‘best’ partition from among a class of regular Boolean expressions. Features of the method are described, including how to measure partition homogeneity, complexity penalizing, search strategies and subgroup definition and representation. The approach is illustrated with analyses of predictors of low birth weight and predictors of impaired glucose tolerance for scree

ISSN:0277-6715    

DOI:10.1002/sim.4780142405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA non‐exhaustive but nevertheless wide‐ranging if biased and personal view of various matters affecting the allocation of treatments to patients in controlled clinical trials will be undertaken from the standpoint of a statistician working in drug development. The following topics are considered: the use of ‘placebos’ in the run‐in phase; the use of crossover trials; selection of patients; various matters concerning centres; two extreme alternatives to randomization, and various matters linking blinding and a

ISSN:0277-6715    

DOI:10.1002/sim.4780142406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA simple form of non‐ignorable missing data mechanisms based on two parameters is used to characterize the amount of missing data and the severity of non‐randomness in clinical trials. Based on the formulation, the effect of non‐randomly missing data on simple analyses which ignore the missing data is studied for binary and normally distributed response variables. In general, the effect of the non‐randomly missing data on the bias and the power increases with the severity of non‐randomness. The bias can be positive or negative and the power can be less than or greater than when the data are missing at random. The results of the analysis, ignoring the missing data, can be seriously flawed if the non‐randomness is severe, even when only a small proportion of the sample is missing. The problem is more pronounced in the case of normally distributed response variables with unequa

ISSN:0277-6715    

DOI:10.1002/sim.4780142407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractCurrent methods for meta‐analysis still leave a number of unresolved issues, such as the choice between fixed‐ and random‐effects models, the choice of population distribution in a random‐effects analysis, the treatment of small studies and extreme results, and incorporation of study‐specific covariates. We describe how a full Bayesian analysis can deal with these and other issues in a natural way, illustrated by a recent published example that displays a number of problems. Such analyses are now generally available using the BUGS implementation of Markov chain Monte Carlo numerical integration techniques. Appropriate proper prior distributions are derived, and sensitivity analysis to a variety of prior assumptions carried out. Current methods are briefly summarized and compared to the full Bayes

ISSN:0277-6715    

DOI:10.1002/sim.4780142408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractNon‐parametric methods have recently been proposed to take into account the recurrent nature of complications in clinical trials, by estimating the prevalenceQ(t), defined as the probability of relapse‐free patients being in a complication state at timet. Recoveries are also considered. These methods have been adapted in this paper to take into consideration not only the recurrent nature of complications but also their severity through the interpretation of average weight functions. Results of a randomized trial comparing late complications following two alternative doses of pre‐operative internal brachytherapy in patients with localized stage cervix carcinoma are used to illustrate the me

ISSN:0277-6715    

DOI:10.1002/sim.4780142409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe goal of screening programmes for cancer is early detection and treatment with a consequent reduction in mortality from the disease. Screening programmes need to assess the true benefit of screening, that is, the length of time of extension of survival beyond the time of advancement of diagnosis (lead‐time). This paper presents a non‐parametric method to estimate the survival function of the post‐lead‐time survival (or extra survival time) of screen‐detected cancer cases based on the observed total life time, namely, the sum of the lead‐time and the extra survival time. We apply the method to the well‐known data set of the HIP (Health Insurance Plan of Greater New York) breast cancer screening study. We make comparisons with the survival of other groups of cancer cases not detected by screening such as interval cases, cases among individuals who refused screening, and randomized control cases. As compared with Walter and Stitt's model, in which they made parametric assumptions for the extra survival time, our non‐parametric method provides a better fit to HIP data in the sense that our estimator for the total survival time has a smaller sum of squar

ISSN:0277-6715    

DOI:10.1002/sim.4780142410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA statistical model for interval censored data is described. Assuming a piecewise constant incidence enables us to analyse very unbalanced data in a generalized linear model. The distribution of age at first appearance ofP. falciparumparasites in infants in Liberia has been estimated. A new graphical method for presentation of test results on all children was developed. In an illness—death model it is described how the proportion of undetected and detected malaria parasitemias depends on parasite rates and testing frequency. The incidence of detectable malaria parasitemia was 0·14 per month in infants under 4 months of age, and 0·60 per month in children over 4 months (p<0001). The congenital resistance to malaria in African infants living in a highly endemic area had largely disappeared by the age of 4 months; before this age children were partly protec

ISSN:0277-6715    

DOI:10.1002/sim.4780142411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY