首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到13条相似文献,搜索用时 3 毫秒
1.
We review and develop pointwise confidence intervals for a survival distribution with right‐censored data for small samples, assuming only independence of censoring and survival. When there is no censoring, at each fixed time point, the problem reduces to making inferences about a binomial parameter. In this case, the recently developed beta product confidence procedure (BPCP) gives the standard exact central binomial confidence intervals of Clopper and Pearson. Additionally, the BPCP has been shown to be exact (gives guaranteed coverage at the nominal level) for progressive type II censoring and has been shown by simulation to be exact for general independent right censoring. In this paper, we modify the BPCP to create a ‘mid‐p’ version, which reduces to the mid‐p confidence interval for a binomial parameter when there is no censoring. We perform extensive simulations on both the standard and mid‐p BPCP using a method of moments implementation that enforces monotonicity over time. All simulated scenarios suggest that the standard BPCP is exact. The mid‐p BPCP, like other mid‐p confidence intervals, has simulated coverage closer to the nominal level but may not be exact for all survival times, especially in very low censoring scenarios. In contrast, the two asymptotically‐based approximations have lower than nominal coverage in many scenarios. This poor coverage is due to the extreme inflation of the lower error rates, although the upper limits are very conservative. Both the standard and the mid‐p BPCP methods are available in our bpcp R package. Published 2016. This article is US Government work and is in the public domain in the USA.  相似文献   

2.
Age–period–cohort (APC) analysis is widely used in cancer epidemiology to model trends in cancer rates. We develop methods for comparative APC analysis of two independent cause‐specific hazard rates assuming that an APC model holds for each one. We construct linear hypothesis tests to determine whether the two hazards are absolutely proportional or proportional after stratification by cohort, period, or age. When a given proportional hazards model appears adequate, we derive simple expressions for the relative hazards using identifiable APC parameters. To demonstrate the utility of these new methods, we analyze cancer incidence rates in the United States in blacks versus whites for selected cancers, using data from the National Cancer Institute's Surveillance, Epidemiology, and End Results Program. The examples illustrate that each type of proportionality may be encountered in practice. Published in 2010 by John Wiley & Sons, Ltd.  相似文献   

3.
Continuous‐time multistate survival models can be used to describe health‐related processes over time. In the presence of interval‐censored times for transitions between the living states, the likelihood is constructed using transition probabilities. Models can be specified using parametric or semiparametric shapes for the hazards. Semiparametric hazards can be fitted using P‐splines and penalised maximum likelihood estimation. This paper presents a method to estimate flexible multistate models that allow for parametric and semiparametric hazard specifications. The estimation is based on a scoring algorithm. The method is illustrated with data from the English Longitudinal Study of Ageing.  相似文献   

4.
In cancer clinical trials, patients often experience a recurrence of disease prior to the outcome of interest, overall survival. Additionally, for many cancers, there is a cured fraction of the population who will never experience a recurrence. There is often interest in how different covariates affect the probability of being cured of disease and the time to recurrence, time to death, and time to death after recurrence. We propose a multi‐state Markov model with an incorporated cured fraction to jointly model recurrence and death in colon cancer. A Bayesian estimation strategy is used to obtain parameter estimates. The model can be used to assess how individual covariates affect the probability of being cured and each of the transition rates. Checks for the adequacy of the model fit and for the functional forms of covariates are explored. The methods are applied to data from 12 randomized trials in colon cancer, where we show common effects of specific covariates across the trials. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

5.
A fundamental challenge in meta‐analyses of published epidemiological dose–response data is the estimate of the function describing how the risk of disease varies across different levels of a given exposure. Issues in trend estimate include within studies variability, between studies heterogeneity, and nonlinear trend components. We present a method, based on a two‐step process, that addresses simultaneously these issues. First, two‐term fractional polynomial models are fitted within each study included in the meta‐analysis, taking into account the correlation between the reported estimates for different exposure levels. Second, the pooled dose–response relationship is estimated considering the between studies heterogeneity, using a bivariate random‐effects model. This method is illustrated by a meta‐analysis aimed to estimate the shape of the dose–response curve between alcohol consumption and esophageal squamous cell carcinoma (SCC). Overall, 14 case–control studies and one cohort study, including 3000 cases of esophageal SCC, were included. The meta‐analysis provided evidence that ethanol intake was related to esophageal SCC risk in a nonlinear fashion. High levels of alcohol consumption resulted in a substantial risk of esophageal SCC as compared to nondrinkers. However, a statistically significant excess risk for moderate and intermediate doses of alcohol was also observed, with no evidence of a threshold effect. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

6.
The use of individual participant data (IPD) from multiple studies is an increasingly popular approach when developing a multivariable risk prediction model. Corresponding datasets, however, typically differ in important aspects, such as baseline risk. This has driven the adoption of meta‐analytical approaches for appropriately dealing with heterogeneity between study populations. Although these approaches provide an averaged prediction model across all studies, little guidance exists about how to apply or validate this model to new individuals or study populations outside the derivation data. We consider several approaches to develop a multivariable logistic regression model from an IPD meta‐analysis (IPD‐MA) with potential between‐study heterogeneity. We also propose strategies for choosing a valid model intercept for when the model is to be validated or applied to new individuals or study populations. These strategies can be implemented by the IPD‐MA developers or future model validators. Finally, we show how model generalizability can be evaluated when external validation data are lacking using internal–external cross‐validation and extend our framework to count and time‐to‐event data. In an empirical evaluation, our results show how stratified estimation allows study‐specific model intercepts, which can then inform the intercept to be used when applying the model in practice, even to a population not represented by included studies. In summary, our framework allows the development (through stratified estimation), implementation in new individuals (through focused intercept choice), and evaluation (through internal–external validation) of a single, integrated prediction model from an IPD‐MA in order to achieve improved model performance and generalizability. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

7.
Objective : The Western Desert Kidney Health Project (WDKHP) is an innovative clinical screening, arts–health and community development program, staffed by Aboriginal health workers. The WDKHP is aimed at prevention and early detection, improving the chance of better management of kidney disease among people in 10 predominantly Aboriginal communities in rural Western Australia. This paper aimed to understand community responses to the WDKHP in three of these communities. Methods : Interviews were undertaken with 26 Aboriginal people living in three remote communities. Community responses were analysed with attention to the social organisation of participants in each community and a focus on the perspectives of key groups, identified here as ‘Community Leaders’, ‘Homelanders’, ‘Refuge Seekers’ and ‘Dislocated’. Results : Participants from all groups reported that the WDKHP was highly acceptable, and an effective means of drawing attention to the need for prevention, early detection and management of diabetes and kidney disease. The integration of Aboriginal health workers to explain the project contributed to the high rates of participation in clinical screening. Conclusions : Outreach clinical services can be an appropriate method of engaging people in remote communities in addressing diabetes and kidney disease. Implications : The remote community setting can act as an ‘enabler’ of healthy lifestyle for Aboriginal people, particularly when augmented by well‐designed outreach programs.  相似文献   

8.
9.
10.
11.
12.
13.

Aim

To describe the study protocol of the MEDiterranean ISlands‐Australia (MEDIS‐Australia) Study modelled on the MEDIS Study conducted in Greece. The present study aims to explore adherence to the traditional Mediterranean diet pattern, determine enablers and barriers to adherence, explore the definition of Greek cuisine, and associations between adherence to the diet pattern and risk factors for cardiovascular disease (CVD) and metabolic syndrome in older Greek Australians originally from Greek islands and Cyprus. Now long‐term immigrants, with at least 50 years in Australia, characteristics and risk factor profiles of older Greek islander‐born Australians will be compared and contrasted to their counterparts living on Greek islands to evaluate the influence of migration on adherence.

Methods

The present study is an observational study of cross‐sectional design using a modified lifestyle and semi‐quantitative food frequency questionnaire to capture sociodemographic, health, psychosocial and dietary characteristics, including cuisine, of 150 older Greek islander‐born Australians. Anthropometric measures and medical history will be collected. Participants will be aged over 65 years, live independently, are originally from a Greek island and are free from CVD.

Results

Data collection is underway.

Conclusions

Characteristics and behaviours associated with adherence, if identified, could be evaluated in future studies. For example, exploration of enablers or barriers to adherence to a Mediterranean dietary pattern in an Australian population.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号