摘要:

AbstractMeta‐analyses using updated individual patient data may provide the most reliable means of combining data from similar randomized controlled trials. The benefits of this approach to systematic reviews are described. Guidance, based on the experience of several groups who have undertaken such projects, is given. This includes practical advice on initiating and maintaining collaboration, the time and resources required to undertake these usually international projects and methods of data checking and validation. Example proforma are include

ISSN:0277-6715    

DOI:10.1002/sim.4780141902

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

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper describes a method for planning the duration of a randomized parallel group study in which the response of interest is a potentially recurrent event. At the design stage we assume patients accrue at a constant rate, we model events via a homogeneous Poisson process, and we utilize an independent exponential censoring mechanism to reflect loss to follow‐up. We derive the appropriate study duration to ensure satisfaction of power requirements for the effect size of interest under a Poisson regression model. An application to a kidney transplant study illustrates the potential savings of the Possion‐based design relative to a design based on the time to the first event. Revised design criteria are also derived to accomodate overdispersed Poisson count data. We examine the frequency properties of two non‐parametric tests recently proposed by Lawless and Nadeau for trials based on the above design criteria. In simulation studies involving homogeneous and non‐homogeneous Poisson processes they performed well with respect to their type I error rate and power. Results from supplementary simulation studies indicate that these tests are also robust to extra‐Posson variation and to clustering in the event times, making these tests attractive in their generality. We illustrate both tests by application to data from a completed kidney transpl

ISSN:0277-6715    

DOI:10.1002/sim.4780141903

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

年代:1995

数据来源: WILEY

摘要:

AbstractPatients are eligible for accrual onto a phase I autologous tumour vaccine clinical trial if their resected and dissociated tumour achieves a minimum viable cell count. Because tumour pre‐processing and cell count determination are expensive, there has been developed a screening procedure based on tumour mass to screen out those tumours unlikely to yield sufficient viable cells. If θ is the ratio of the expected benefit of an accrual onto the study to the cost of tumour pre‐processing and cell counting, then we maximize long‐run benefit by pre‐processing and counting only those tumours whose masses exceed a cutoffmc, such that Pr {sufficient tumour cells mass =mc} = 1/θ. We derive algorithms for estimatingmcand evaluate them under a variety of assumptions concerning the cell count/mass relationship. These include explicit equations formcunder parametric assumptions as well as more general algorithms based on non‐parametric smoothing techniques. We show that when θ deviates substantially from 2, these methods outperform simple inverse i

ISSN:0277-6715    

DOI:10.1002/sim.4780141904

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

年代:1995

数据来源: WILEY

摘要:

AbstractI derive the locally most powerful rank tests for acceleration against semi‐parametric alternatives when some patients are cured of the disease. I consider some particular classes of alternatives and present simulation results to verify the validity of the proposed tests. Real data from clinical trials for childhood leukaemia illustrate the proposed test

ISSN:0277-6715    

DOI:10.1002/sim.4780141905

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

年代:1995

数据来源: WILEY

摘要:

AbstractWe incorporate a cubic spline function where the tails are linearly constrained, as the baseline hazard, into the proportional hazards model. We show estimation of covariable coefficients and survival probabilities with this model to be as efficient statistically as with the Cox proportional hazards model when covariables are fixed. Examples show that the inclusion of time‐dependent covariables defined as step functions into the restricted cubic spline proportional hazards model reduces computation time by a factor of 213 over the Cox model. Advantages of the spline model also include flexibility of the hazard, smooth survival curves, and confidence limits for the survival and hazard estimates when there are time‐dependent covariables pres

ISSN:0277-6715    

DOI:10.1002/sim.4780141906

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

年代:1995

数据来源: WILEY

摘要:

AbstractWe consider the problem of interpreting categorical regression models, such as the polytomous logistic model, the continuation‐ratio model, the stereotype model, and the cumulative‐odds model. We present a method to convert categorical regression coefficients into estimates of standardized fitted probabilities, probability differences and probability ratios. We use a delta‐method approach to estimate standard errors. We then present a small simulation study to compare different transforms for setting confidence limits, and provide an illustration of our approach in an observational study of drug therapy of polymyo

ISSN:0277-6715    

DOI:10.1002/sim.4780141907

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

年代:1995

数据来源: WILEY

摘要:

AbstractWe provide an alternative to the maximum likelihood method for making inferences about the parameters of the logistic regression model. The method is based appropriate permutational distributions of sufficient statistics. It is useful for analysing small or unbalanced binary data with covariates. It also applies to small‐sample clustered binary data. We illustrate the method by analysing several biomedical data set

ISSN:0277-6715    

DOI:10.1002/sim.4780141908

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

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper considers an index of hospital quality performance defined as the ratio of the observed number deaths to the number predicted by a fitted logistic regression model. We study tests and confidence intervals under two different scenarios depending on the availability of an estimate of the covariance matrix of the coefficints from the fitted logistic regression model. We propose parametric as well as bootstrap‐based confidence intervals. We apply the methods to an analysis of the performance of 27 intensive care unit

ISSN:0277-6715    

DOI:10.1002/sim.4780141909

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.4780141901

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

年代:1995

数据来源: WILEY