ISSN:0277-6715    

DOI:10.1002/sim.4780080602

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

年代:1989

数据来源: WILEY

摘要:

AbstractThis paper presents a graphical method for converting relative risks to absolute risks. These absolute risk estimates are a function of the patient's current age, the patient's risk of developing cancer relative to some baseline population, the age specific cancer hazard in the baseline population, and the patient's competing mortal risk from all other causes. Graphs for breast cancer morbidity in women, cardiovascular mortality in men, and lung cancer morbidity in men illustrate the method. These graphs provide the probability of developing cancer in the next twenty years given the patient's current age and relative risk. They are derived under the proportional hazards model. A graph for lung cancer in men that uses a plausible exponential hazards model is also provided. The paper illustrates the importance of competing mortal hazard from other causes on absolute cancer risk. The strengths and weaknesses of this method are discussed. The graphs presented in this paper may be used as an aid in clinical decision making and in patient counselling.

ISSN:0277-6715    

DOI:10.1002/sim.4780080603

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe statistical and epidemiologic literatures contain many examples of the reanalyses of medical databases. Some are confirmatory, such as the many reanalyses of the Stanford heart transplant data. Others, however, concern issues that differ from those that the data originally intended to address. We demonstrate in this paper that the second kind of reanalysis, if undertaken uncritically, can produce biased results. Utilizing a log‐linear model, we show analytically that the reanalysis of a designed study without adjustment for the design variable can produce biased results. We express the magnitude of this bias as a function of second‐ and third‐order interactions in the data. We demonstrate further that preliminary testing for the existence of second‐ and third‐order interactions can provide substantial bias

ISSN:0277-6715    

DOI:10.1002/sim.4780080604

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

年代:1989

数据来源: WILEY

ISSN:0277-6715    

DOI:10.1002/sim.4780080605

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

年代:1989

数据来源: WILEY

ISSN:0277-6715    

DOI:10.1002/sim.4780080606

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

年代:1989

数据来源: WILEY

ISSN:0277-6715    

DOI:10.1002/sim.4780080607

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

年代:1989

数据来源: WILEY

摘要:

AbstractIn epidemiologic studies of the effect of an exposure on disease, the crude association of exposure with disease may fail to reflect a causal association due to confounding by one or more covariates. Most previous discussions of confounding in the epidemiologic literature have considered only point exposure studies, that is, studies that measure exposure and covariate status only once, at start of follow‐up. In this paper we offer definitions of confounding suitable for longitudinal studies that obtain data on exposure, covariate, and vital status at several points in time. An important difference between longitudinal studies and point exposure studies is that, in longitudinal studies, a time‐dependent covariate can be simultaneously a confounder and an intermediate variable on the causal pathway from exposure to disease. In this paper I propose an estimator, the extended standardized risk difference, that provides control for confounding by a covariate that is simultaneously a confounder and an intermediate varia

ISSN:0277-6715    

DOI:10.1002/sim.4780080608

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

年代:1989

数据来源: WILEY

摘要:

AbstractThree kinds of generalized residuals based on probability integral transformation are defined and their roles in graphical goodness of fit testing are discussed. Although they are useful in fitting parametric distributions, their value is questionable, however, in fitting Cox's proportional hazard rate (PHR) models. They almost always appear to give a good fit because of (a) almost non‐parametric nature of the PHR models; (b) heavy right‐hand censoring in epidemiological data; and (c) scale adjustment in graphical presentation. Thus, the apparent overall fit has little inferential meaning, but the residuals are useful in exploratory analysis. A simple method, based on non‐parametric stratified residual plots, for selection of risk factors is discussed. It is, in fact, equivalent to comparison of several empirical survival functions, one for each set of values (stratum) of a covariable under consideration. It is also suggested that for the preliminary PHR model, the continuous variables should be discretized and indicator variables used in the model to check analytically the graphical perception of the possible functional form of the contribution of each covariable to the PHR

ISSN:0277-6715    

DOI:10.1002/sim.4780080609

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

年代:1989

数据来源: WILEY

摘要:

AbstractThis paper develops a parametric model for time to seroconversion after experimental bovine leukaemia virus (BLV) infection, and examines the effects of inoculation route, volume of inoculum, type of inoculation material, and antigen status of donor on seroconversion time. We used parametric and nonparametric statistical methodology to analyse interval data on 150 animals from 13 published reports. The log‐logistic model fitted the observed times to seroconversion better than the log‐normal or Weibull models, which were the considered alternati

ISSN:0277-6715    

DOI:10.1002/sim.4780080610

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

年代:1989

数据来源: WILEY

摘要:

AbstractDay and Walter derived methods of joint maximum likelihood estimation for the sojourn time distribution and the false negative rate for a screening programme. Their methods are not directly applicable to a programme which uses alternate screening by two modalities whose sojourn times and false negative rates will differ. A modification is proposed and the results applied to data from the Edinburgh Randomised Trial of Breast Cancer Screening. This enables the effects of mammography and clinical examination to be separated. It is estimated that in a programme using both modalities 79 per cent of tumours arising in regularly screened women would be detected by screening and if the clinical examination were omitted this figure would be reduced by 5 per cent. The confidence intervals are, however, quite wide.

ISSN:0277-6715    

DOI:10.1002/sim.4780080611

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

年代:1989

数据来源: WILEY