共查询到20条相似文献，搜索用时 15 毫秒
1.
Harold M. Hudson Serigne N. Lô R. John Simes Andrew M. Tonkin Stephane Heritier 《Statistics in medicine》2014,33(10):1621-1645
Transform methods have proved effective for networks describing a progression of events. In semi‐Markov networks, we calculated the transform of time to a terminating event from corresponding transforms of intermediate steps. Saddlepoint inversion then provided survival and hazard functions, which integrated, and fully utilised, the network data. However, the presence of censored data introduces significant difficulties for these methods. Many participants in controlled trials commonly remain event‐free at study completion, a consequence of the limited period of follow‐up specified in the trial design. Transforms are not estimable using nonparametric methods in states with survival truncated by end‐of‐study censoring. We propose the use of parametric models specifying residual survival to next event. As a simple approach to extrapolation with competing alternative states, we imposed a proportional incidence (constant relative hazard) assumption beyond the range of study data. No proportional hazards assumptions are necessary for inferences concerning time to endpoint; indeed, estimation of survival and hazard functions can proceed in a single study arm. We demonstrate feasibility and efficiency of transform inversion in a large randomised controlled trial of cholesterol‐lowering therapy, the Long‐Term Intervention with Pravastatin in Ischaemic Disease study. Transform inversion integrates information available in components of multistate models: estimates of transition probabilities and empirical survival distributions. As a by‐product, it provides some ability to forecast survival and hazard functions forward, beyond the time horizon of available follow‐up. Functionals of survival and hazard functions provide inference, which proves sharper than that of log‐rank and related methods for survival comparisons ignoring intermediate events. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
2.
The weighted Kaplan–Meier (WKM) estimator is often used to incorporate prognostic covariates into survival analysis to improve efficiency and correct for potential bias. In this paper, we generalize the WKM estimator to handle a situation with multiple prognostic covariates and potential‐dependent censoring through the use of prognostic covariates. We propose to combine multiple prognostic covariates into two risk scores derived from two working proportional hazards models. One model is for the event times. The other model is for the censoring times. These two risk scores are then categorized to define the risk groups needed for the WKM estimator. A method of defining categories based on principal components is proposed. We show that the WKM estimator is robust to misspecification of either one of the two working models. In simulation studies, we show that the robust WKM approach can reduce bias due to dependent censoring and improve efficiency. We apply the robust WKM approach to a prostate cancer data set. Copyright 2010 John Wiley & Sons, Ltd. 相似文献
3.
In two‐stage randomization designs, patients are randomized to one of the initial treatments, and at the end of the first stage, they are randomized to one of the second stage treatments depending on the outcome of the initial treatment. Statistical inference for survival data from these trials uses methods such as marginal mean models and weighted risk set estimates. In this article, we propose two forms of weighted Kaplan–Meier (WKM) estimators based on inverse‐probability weighting—one with fixed weights and the other with time‐dependent weights. We compare their properties with that of the standard Kaplan–Meier (SKM) estimator, marginal mean model‐based (MM) estimator and weighted risk set (WRS) estimator. Simulation study reveals that both forms of weighted Kaplan–Meier estimators are asymptotically unbiased, and provide coverage rates similar to that of MM and WRS estimators. The SKM estimator, however, is biased when the second randomization rates are not the same for the responders and non‐responders to initial treatment. The methods described are demonstrated by applying to a leukemia data set. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
4.
This paper introduces a new simple divergence measure between two survival distributions. For two groups of patients, the divergence measure between their associated survival distributions is based on the integral of the absolute difference in probabilities that a patient from one group dies at time t and a patient from the other group survives beyond time t and vice versa. In the case of non‐crossing hazard functions, the divergence measure is closely linked to the Harrell concordance index, C, the Mann–Whitney test statistic and the area under a receiver operating characteristic curve. The measure can be used in a dynamic way where the divergence between two survival distributions from time zero up to time t is calculated enabling real‐time monitoring of treatment differences. The divergence can be found for theoretical survival distributions or can be estimated non‐parametrically from survival data using Kaplan–Meier estimates of the survivor functions. The estimator of the divergence is shown to be generally unbiased and approximately normally distributed. For the case of proportional hazards, the constituent parts of the divergence measure can be used to assess the proportional hazards assumption. The use of the divergence measure is illustrated on the survival of pancreatic cancer patients. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
5.
Clustered right‐censored data often arise from tumorigenicity experiments and clinical trials. For testing the equality of two survival functions, Jung and Jeong extended weighted logrank (WLR) tests to two independent samples of clustered right‐censored data, while the weighted Kaplan–Meier (WKM) test can be derived from the work of O'Gorman and Akritas. The weight functions in both classes of tests (WLR and WKM) can be selected to be more sensitive to detect a certain alternative; however, since the exact alternative is unknown, it is difficult to specify the selected weights in advance. Since WLR is rank‐based, it is not sensitive to the magnitude of the difference in survival times. Although WKM is constructed to be more sensitive to the magnitude of the difference in survival times, it is not sensitive to late hazard differences. Therefore, in order to combine the advantages of these two classes of tests, this paper developed a class of versatile tests based on simultaneously using WLR and WKM for two independent samples of clustered right‐censored data. The comparative results from a simulation study are presented and the implementation of the versatile tests to two real data sets is illustrated. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
6.
Prognostic studies are widely conducted to examine whether biomarkers are associated with patient's prognoses and play important roles in medical decisions. Because findings from one prognostic study may be very limited, meta‐analyses may be useful to obtain sound evidence. However, prognostic studies are often analyzed by relying on a study‐specific cut‐off value, which can lead to difficulty in applying the standard meta‐analysis techniques. In this paper, we propose two methods to estimate a time‐dependent version of the summary receiver operating characteristics curve for meta‐analyses of prognostic studies with a right‐censored time‐to‐event outcome. We introduce a bivariate normal model for the pair of time‐dependent sensitivity and specificity and propose a method to form inferences based on summary statistics reported in published papers. This method provides a valid inference asymptotically. In addition, we consider a bivariate binomial model. To draw inferences from this bivariate binomial model, we introduce a multiple imputation method. The multiple imputation is found to be approximately proper multiple imputation, and thus the standard Rubin's variance formula is justified from a Bayesian view point. Our simulation study and application to a real dataset revealed that both methods work well with a moderate or large number of studies and the bivariate binomial model coupled with the multiple imputation outperforms the bivariate normal model with a small number of studies. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
7.
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
8.
9.
目的探讨东莞地区宫颈癌及宫颈上皮内瘤变（CIN）中不同类型人乳头瘤病毒（HPv）的感染及分型情况。方法回顾性研究东莞康华医院妇科已经确诊的宫颈癌及CIN患者,采用凯普核酸分子快速导流杂交基因芯片技术对HPV进行分型。结果①各级别CIN及宫颈癌以HPV高危型单一或多重感染为主,219例宫颈癌及CIN患者,单一高危型别感染105例（47．95％）,多重感染47例（21．46％）,低危型别感染9例（4．11％）,HPV检测阴性58例（26．48％）;②在HPV阳性的161例患者中,单一感染者114例（70．81％）,双重感染36例（22．36％）,三重感染8例（4．97％）,四重感染3例（1．86％）;⑨HPV16、52、33感染率最高,分别为26．48％、5．94％、5．（13％。结论HPV以高危型单一或多重感染为主;随CIN级别的增高,HPV感染率呈上升趋势;无论单一还是多重感染,尤以HPV16、52、33亚型的感染率最高。 相似文献
10.
Rodney A. Sparapani Brent R. Logan Robert E. McCulloch Purushottam W. Laud 《Statistics in medicine》2016,35(16):2741-2753
Bayesian additive regression trees (BART) provide a framework for flexible nonparametric modeling of relationships of covariates to outcomes. Recently, BART models have been shown to provide excellent predictive performance, for both continuous and binary outcomes, and exceeding that of its competitors. Software is also readily available for such outcomes. In this article, we introduce modeling that extends the usefulness of BART in medical applications by addressing needs arising in survival analysis. Simulation studies of one‐sample and two‐sample scenarios, in comparison with long‐standing traditional methods, establish face validity of the new approach. We then demonstrate the model's ability to accommodate data from complex regression models with a simulation study of a nonproportional hazards scenario with crossing survival functions and survival function estimation in a scenario where hazards are multiplicatively modified by a highly nonlinear function of the covariates. Using data from a recently published study of patients undergoing hematopoietic stem cell transplantation, we illustrate the use and some advantages of the proposed method in medical investigations. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
11.
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
12.
Competing risks arise with time‐to‐event data when individuals are at risk of more than one type of event and the occurrence of one event precludes the occurrence of all other events. A useful measure with competing risks is the cause‐specific cumulative incidence function (CIF), which gives the probability of experiencing a particular event as a function of follow‐up time, accounting for the fact that some individuals may have a competing event. When modelling the cause‐specific CIF, the most common model is a semi‐parametric proportional subhazards model. In this paper, we propose the use of flexible parametric survival models to directly model the cause‐specific CIF where the effect of follow‐up time is modelled using restricted cubic splines. The models provide smooth estimates of the cause‐specific CIF with the important advantage that the approach is easily extended to model time‐dependent effects. The models can be fitted using standard survival analysis tools by a combination of data expansion and introducing time‐dependent weights. Various link functions are available that allow modelling on different scales and have proportional subhazards, proportional odds and relative absolute risks as particular cases. We conduct a simulation study to evaluate how well the spline functions approximate subhazard functions with complex shapes. The methods are illustrated using data from the European Blood and Marrow Transplantation Registry showing excellent agreement between parametric estimates of the cause‐specific CIF and those obtained from a semi‐parametric model. We also fit models relaxing the proportional subhazards assumption using alternative link functions and/or including time‐dependent effects. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
13.
目的评价人乳头瘤病毒(Human Papillomavirus,HPV)感染在宫颈病变早期筛查中的作用,为进一步诊断和判断预后提供依据。方法来我院进行宫颈癌筛查,因宫颈液基薄层细胞学检查存在异常细胞妇女413例,均进行阴道镜下组织活检和HPV-DNA分型。结果上皮内瘤样病变(CIN)I患者中以ASCUS检出符合率最高,CIN II患者中以LSIL检出符合率最高,CIN III患者中以HSIL检出符合率最高。慢性宫颈炎患者一种或多种高危型HPV(HR-HPV)感染率要低于CIN患者(χ2=32.105,P=0.000),宫颈癌HR-HPV感染率为100%;慢性宫颈炎患者与CIN患者低危型HPV(LR-HPV)感染率比较,差异无统计学意义(χ2=0.205,P=0.650)。宫颈病变患者以单一HR-HPV亚型感染更常见。结论宫颈癌及癌前病变与HPV感染密切相关,HR-HPV基因检测及分型在宫颈病变的预后判断、疗效监测等方面具有重要价值。 相似文献
14.
S. K. Njagi N. R. Mugo A. J. Reid S. Satyanarayana K. Tayler-Smith W. Kizito J. Kwatampora W. Waweru J. Kimani J. S. Smith 《Public Health Action》2013,3(4):271-275
Setting:
Sex Workers Outreach Programme Clinic, Korogocho, Nairobi, Kenya.Objective:
In a cohort of sex workers, to determine 1) the prevalence of cervical intra-epithelial neoplasia (CIN) and its association with human immunodeficiency virus-1 (HIV-1) infection, and 2) the incidence rate of CIN during the 3-year follow-up from December 2009 to December 2012.Design:
Prospective nested cohort study.Results:
Of the 350 women enrolled, the median age was 29 years (range 18–49); 84 (24%) were HIV-1-infected. At enrollment, 54 (15%) had an abnormal cytology, 39 (11%) had low-grade intra-epithelial lesions (LSIL) and 15 (4%) high-grade intraepithelial lesions (HSIL). HIV-1-infected women were 2.7 times (95%CI 1.7–4.4) more likely to have CIN than non-HIV-1-infected women. Among HIV-1-infected women, the prevalence of LSIL and HSIL was 2.5 times (95%CI 1.2–5.1) and seven times (95%CI 2.3–23.3) greater than among non-HIV-infected women. During the follow-up period, 39 (11%) women had incident CIN (6.6/100 person years [py]), with no difference by HIV status, i.e., respectively 7.9/100 py and 6.3/100 py in HIV-1-infected and non-HIV-1-infected women.Conclusion:
The prevalence and incidence of CIN among HIV-1-infected sex workers was high; early, regular screening and follow-up of this life-threatening condition is therefore recommended. 相似文献15.
陈金顺 《中国实用乡村医生杂志》2014,(14):44-46
目的探讨液基细胞学检查（TCT）与人乳头状瘤病毒（HPV）检测及阴道镜联合应用对宫颈癌诊断的临床意义及应用价值。方法回顾分析300例高危型HPV检测及TCT检查,对其中一项或两项异常者做阴道镜病理活检,宫颈上皮内瘤变（CIN）及以上病变为病理阳性,对病理结果阳性患者进行结果分析。结果单独HPV（H组）DNA检测阳性35例,病理结果阳性21例,符合率60.0%;单独TCT（T组）检查阳性33例,病理结果阳性24例,符合率72.7%;HPV及TCT检测（H＋T组）均为阳性20例,病理结果阳性19例,符合率95.0%。与H组及T组比较,H＋T组符合率差异有统计学意义（P＜0.01）。结论 HPV及TCT与阴道镜联合检测宫颈癌可大大提高早期诊断的检出率,值得临床推广。 相似文献
16.
The majority of staging systems focus on the definition of stage, and, therefore, prediction of prognosis. In the current era of clinical trial research, it has become apparent that the clinical stage alone is not sufficient to assess patient risk of treatment failure. As the number of biological markers increases, our ability to partition the traditional disease classification system improves, and our ability to predict patient success continues to increase. One approach to quantifying individual patient risk is through the nomogram. Nomograms are graphical representations of statistical models, which provide the probability of treatment outcome based on patient-specific covariates. We will focus on the use of the nomogram when the response variable is time to failure and there are multiple, possibly dependent, competing causes of failure. In this setting, estimation of the failure probability through direct application of the Cox proportional hazards model provides the probability of failure (for example, death from cancer) assuming failure from a dependent competing cause will not occur. In many clinical settings this is an unrealistic assumption. The purpose of this study is to illustrate the use of the conditional cumulative incidence function for providing a patient-specific prediction of the probability of failure in the setting of competing risks. A competing risks nomogram is produced to estimate the probability of death due to sarcoma for patients who have already developed a local recurrence of their initially treated soft-tissue sarcoma. 相似文献
17.
In survival analysis with competing risks, the transformation model allows different functions between the outcome and explanatory variables. However, the model's prediction accuracy and the interpretation of parameters may be sensitive to the choice of link function. We review the practical implications of different link functions for regression of the absolute risk (or cumulative incidence) of an event. Specifically, we consider models in which the regression coefficients β have the following interpretation: The probability of dying from cause D during the next t years changes with a factor exp(β) for a one unit change of the corresponding predictor variable, given fixed values for the other predictor variables. The models have a direct interpretation for the predictive ability of the risk factors. We propose some tools to justify the models in comparison with traditional approaches that combine a series of cause‐specific Cox regression models or use the Fine–Gray model. We illustrate the methods with the use of bone marrow transplant data. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
18.
人宫颈鳞状细胞癌裸鼠移植模型的建立及分析 总被引：1，自引：0，他引：1
目的:采用裸鼠腹部皮下移植感染高危型HPV人宫颈鳞癌组织的方法,建立宫颈癌动物模型,研究其在裸鼠体内的成瘤性,并探讨其生物学特性。方法:取中分化及高分化人宫颈鳞状细胞癌癌组织两块分别接种于裸鼠腹部皮下,以建立人宫颈癌裸鼠模型,比较两组荷瘤鼠成瘤率、一般特性和移植瘤生长情况,85天后处死裸鼠,切除肿块做病理切片;PCR(聚合酶链式反应)检测肿瘤组织、外周血和肝等脏器HPV DNA表达情况。结果:接种后两组小鼠分别于第42天及第49天在接种部位可见结节,第80天后肿瘤块平均体积分别为(38.0±5.1)mm3、(30.2±4.6)mm3,肿瘤移植成功率分别为80%及60%,移植瘤生长以局部浸润为主,未见转移瘤。组织学检查所有移植瘤与种植前肿瘤组织病理检查结果一致,HPV DNA呈阳性,且为高危型人乳头瘤病毒HPV16、18型阳性,亦与原宫颈癌病人HPV16、HPV18感染一致;外周血与肝等脏器HPV DNA呈阴性。结论:裸鼠人宫颈癌组织模型成瘤率较高,且分化程度越低其成瘤率越高,操作简便,成本低,且保留了HPV感染生物学特性,为探索宫颈癌的发病机制和临床治疗提供了重要的科研工具。 相似文献
19.
目的 了解西安市高校非医学专业女大学生对人乳头瘤病毒(HPV)的认知情况及其对接种HPV疫苗的态度,为制定针对非医学专业大学生健康教育模式,推广HPV疫苗的接种提供依据.方法 采用整群随机抽样的方法,在西安市6所非医学类本科高校中抽取16个专业的大学二、三年级女大学生共2 131名,用自行设计的问卷进行调查,获有效问卷2 096份,有效回收率为98.4％.结果 仅11.3％被调查者知晓HPV,有性生活组大学生对HPV知晓率显著高于无性生活组(x2=20.182,P＜0.05),来自单亲或重组家庭的女大学生对HPV知晓率显著高于来自原生家庭组(x2=4.329,P＜0.05).不同年级间(x2=0.921),来自城市或农村(x2=0.891),是否独生子女(x2 =0.330)组间对HPV知晓率差异无统计学意义(P＞0.05).仅9.7％被调查者知晓HPV疫苗.79.9％的被调查者表示愿意接种HPV疫苗;担心会感染HPV (44.1％)或患宫颈癌(19.3％)的被调查者有较强的接种意愿;公众健康教育(42.2％)及医务人员推荐(34.7％)是女大学生们更愿意接受的疫苗推荐方式.超过半数被调查者(50.1％)能够接受的疫苗价格在50～ 100元.结论 西安非医学专业大学生对HPV及HPV疫苗的知晓率低,但接种意愿强.应加强科普健康教育,普及宫颈癌一级预防、HPV及HPV疫苗相关知识. 相似文献
20.
陈少珍 《中国妇幼卫生杂志》2014,(2):36-37,40
目的了解流动已婚育龄期妇女人乳头状瘤病毒（HPV）感染的现状,探讨影响HPV感染的相关因素。方法选取2011年10—12月间坪山办事处的流动已婚育龄妇女365例,行HPv检查,并对HPV检查异常者行LCT检查,以了解坪山办事处的流动已婚育龄妇女的Hpv感染现状,分析其相关原因。结果365例流动已婚育龄期妇女中,11例出现高危型HPv感染,感染率达3．01％,经LCT检查发现,6例LCT检查正常,3例LCT检查异常,1例在随访期间一直闭经未行LCT检查,1人失访;HPV感染相关因素分析表明,20-30岁女性、初中及以下学历、有（被动）吸烟史、初次性生活年龄〈20岁、生育次数较多、性生活频繁等因素均会导致HPV感染率升高,但组间对比发现,各因素间差异无统计学意义（P〈0．05）。结论深圳市坪山区流动已婚育龄期妇女的高危型HPV感染率为3．01％。HPV感染可能与女性的年龄、文化程度、吸烟（被动）、过早性生活、生育次数、性生活频率等相关。加强HPV感染相关因素的控制,可减少HPV感染的发生几率。 相似文献