摘要:

AbstractThe properties of prenatal infections are studied through the development of a theoretical model. The responses of such epidemic systems to natural changes in transmission rates, age at maternity, social stratification, geographical heterogeneity, epidemic instability and the introduction of vaccination, are examined. The effects of age‐at‐vaccination, efficacy of vaccination, wild virus interaction, and vaccine‐immunity decay rates, are also examined in some detail. Several powerful putative influences upon the evolution of prenatally determined infective diseases are identified. They provide scientific tools for detecting processes of this

ISSN:0277-6715    

DOI:10.1002/sim.4780020102

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

年代:1983

数据来源: WILEY

摘要:

AbstractIn most diseases of contemporary interest to epidemiology, the importance of familial risk factors is often assessed by relative risk measures computed from family history data. In this paper, we examine the efficiency of relative risk measures in discerning the genetic background of a disease. It is shown that even for a simple (one locus, two alleles) genetic disease, incomplete penetrance of the disease allele and/or occurrence of sporadics (i.e. non‐heritable cases caused by environmental risk factors) often yields a rather small value of relative risk. This means that a small value of relative risk need not necessarily imply that genetic factors are unimportant in the aetiology of the disease. Furthermore, it is shown that the relative risk measures are complicated functions of disease gene frequency, the penetrance parameter and the sporadic rate. A rejection of genetic involvement for a disease on the basis of a single relative risk estimate may, therefore, be erroneou

ISSN:0277-6715    

DOI:10.1002/sim.4780020103

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

年代:1983

数据来源: WILEY

摘要:

AbstractClassification errors of dependent variables can distort the results of observational studies. To reduce misclassification from our multicentre observational study of abortion complications, we extended the methodology of Lawrence and Greenwald9for use in situations of unequal sample sizes and implemented both an office review and a field review. We reabstracted 424 reported complications and a random sample of 364 reported non‐serious cases from 12 institutions participating in our study. In total, 30 per cent of the reported serious complications turned out to be misclassified: the office review detected 74 per cent of the total number of misclassifications with the remainder found in the field review. Because, with our particular data base, we estimated expending only 15 per cent of the total resources with our office effort, this represented the most cost‐efficient approach to reducing classification errors. By eliminating the false positives from our study, we forced the specificity to 1·00 which produced both an unbiased estimate of the relative risk and an increase of 4 per cent to 63 per cent in the power of our s

ISSN:0277-6715    

DOI:10.1002/sim.4780020104

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

年代:1983

数据来源: WILEY

摘要:

AbstractBiopsy specimens are taken from the heart at regular intervals during the weeks following cardiac transplantation. Three specimens at most have been taken at each session, and classified by the pathologist on a histological four‐point scale of rejection. Since the rejection reaction in the myocardium is uniform neither in intensity nor distribution, there is often disagreement between the findings from a single session; even after three negative specimens there is some doubt as to whether rejection has taken place. In an attempt to quantify this residual uncertainty, we have adapted a procedure of Dawid and Skene1for ‘estimating error rates’ when the true state is not known. The model is shown to provide a good explanation of the observed data, and provides guidance on the number of negative specimens required to give a defined level of certainty that rejection is not taking

ISSN:0277-6715    

DOI:10.1002/sim.4780020105

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

年代:1983

数据来源: WILEY

摘要:

AbstractRecently there has been considerable discussion concerning the analysis of data and presentation of results from clinical trials in breast cancer. A problem stems from there being several events of interest, notably disease recurrence and death. Current methods based on ‘so‐called’ disease‐free survival are criticized on the grounds that they confuse events, such as disease recurrence and death, in the treatment comparison and consequently could be very misleading. Alternative methods of analysis, based on separate measures of treatment effect are presented and illu

ISSN:0277-6715    

DOI:10.1002/sim.4780020106

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

年代:1983

数据来源: WILEY

摘要:

AbstractThis field study sought to measure the effects of dental delivery and school‐based, dental health education on use of dental health care by children in grades K‐6. We attempted to control for two potential confounding factors by an approximate randomization of children into treatment groups with stratification on grade and initial oral disease levels. A backward elimination log‐linear model selection procedure for the 5‐factor classification permitted tests for higher‐order interaction, namely effect‐modification, confounding and collapsibility. We found that the effect of dental health education on use of dental care depended on the mode of dent

ISSN:0277-6715    

DOI:10.1002/sim.4780020107

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

年代:1983

数据来源: WILEY

摘要:

AbstractThis paper provides an expression for bias of the maximum likelihood logistic regression estimates for use with small sample sizes. This bias correction is based on an expansion of the maximum likelihood equation. Simulation results show these corrections to be highly effective in small samples.

ISSN:0277-6715    

DOI:10.1002/sim.4780020108

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe association between the presence or absence of two HLA antigens and coeliac disease, thyrotoxicosis and ankylosing spondylitis has been studied in patients and controls. The simple empirical logistic model and a refinement due to Dyke and Patterson have been used to examine which conditional associations are important.

ISSN:0277-6715    

DOI:10.1002/sim.4780020109

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

年代:1983

数据来源: WILEY

摘要:

AbstractApproximate standard errors of the probability of a particular diagnosis are given for the predictive and estimative methods described by Aitchison and Dunsmore.1An example used in the detection of carriers of Duchenne muscular dystrophy (DMD) is given for illustration.

ISSN:0277-6715    

DOI:10.1002/sim.4780020110

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

年代:1983

数据来源: WILEY

摘要:

AbstractWe examine the problem of discriminating between two groups in the context of multivariate response curves observed over a specified time interval. We propose a descriptive solution for the case where one can determine the response curves by linear interpolation between successive observations. Unlike most previously reported methods that use only the current multivariate observation, our approach accounts for the history of the process. Moreover the method has the potential advantage of being applicable dynamically, as one observes the multivariate response curve. Finally, the method demonstrates simplicity and flexibility, two important features for successful, routine, clinical application.

ISSN:0277-6715    

DOI:10.1002/sim.4780020111

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

年代:1983

数据来源: WILEY