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1.
队列研究中的依时混杂偏倚和随访时间偏倚   总被引:4,自引:4,他引:0       下载免费PDF全文
【导读】未加识别或控制的混杂因素和偏倚会影响流行病学研究中因果关系的准确判断。目前已熟知队列研究中可能出现的选择偏倚及失访偏倚,为此笔者复习了队列研究中可能存在的依时混杂偏倚及其控制方法,并通过实例提出随访时间偏倚的概念及其控制方法。  相似文献   

2.
空间流行病学中的偏倚与混杂   总被引:1,自引:1,他引:1  
目的探讨空间流行病学中的偏倚与混杂。方法结合实例分析空间流行病学中可能存在偏倚与混杂及其对研究结果的可能影响。结果空间流行病学研究中存在选择性偏倚,确证、分子和分母偏倚,由疾病诱导期/潜隐期的选择和暴露-疾病模式的错误载明所致的偏倚,暴露不准确偏倚,空间相关性,显著性检验,生态学偏倚和社会-经济混杂等8种偏倚与混杂。结论空间流行病学研究中的偏倚来源众多且较为复杂,由此可以夸大或掩盖研究结果,故对研究结果的解释应慎重。  相似文献   

3.
未亡时间偏倚(immortal time bias)又称为保证时间偏倚(guarantee time bias),是一种特殊的选择性偏倚[1],广泛地存在于观察性研究和药物临床试验中。Gail[2]分析心脏移植的研究时,首次提出了未亡时间偏倚,认为移植组生存时间的延长,部分归因于未亡时间偏倚的存在。  相似文献   

4.
疾病空间分布趋势面模型的共线性偏倚及其测量与控制   总被引:1,自引:1,他引:0  
目的探讨趋势面分析中共线性偏倚及其测量与控制方法.方法以疾病监测资料为基础,引用回归诊断方法识别趋势面模型的共线性偏倚,进一步用岭回归趋势面模型控制共线性偏倚.结果趋势面分析往往存在共线性偏倚,利用岭回归趋势面分析可以在一定程度上控制共线性偏倚.结论在作趋势面分析时应当考虑共线性偏倚对结果的影响,并设法予以控制.  相似文献   

5.
目的 了解凉山州昭觉县成年获得性免疫缺陷综合征(acquired immunodeficiency syndrome,AIDS)患者接受抗病毒治疗后的生存状况,并探讨其影响因素。方法 采用回顾性队列研究方法,以昭觉县2005年1月1日~2017年3月20日入组参加抗病毒治疗的成年HIV/AIDS为研究对象,收集其生存死亡信息,采用生存分析方法对研究对象进行生存时间及其影响因素的分析。结果 截止观察日止,2 216例研究对象中仍在治疗者1 528人(68.95%),因艾滋病死亡者222人(10.02%),平均生存时间为17.64月,中位生存时间13月,治疗时间少于12月者99人(44.59%)。第1~5年的累计生存率为0.93、0.90、0.88、0.86、0.85。Cox比例风险回归模型分析显示,年龄、基线CD4+T细胞计数、初始治疗方案、入组治疗时是否存在艾滋病相关疾病或症状是影响生存时间的因素(均有P<0.05)。结论 昭觉县艾滋病抗病毒治疗降低了艾滋病死亡率,延长了患者的生存时间;在抗病毒治疗过程中存在多种因素影响对患者生存状况,及早发现HIV感染者并及时纳入治疗能有效提高高效抗逆转录病毒疗法(highly active antiretroviral therapy,HAART)治疗成效。  相似文献   

6.
艾滋病潜伏期是HIV感染者疾病进展中的重要阶段,本文就其影响因素包括感染年龄、感染途径、潜伏期接受治疗情况、HIV亚型、CD4细胞数和病毒载量等做了系统阐述,并探讨了统计学方法在艾滋病潜伏期研究中的应用及可能存在的偏倚,为今后对艾滋病潜伏期的深入研究奠定了一定的基础。  相似文献   

7.
医院感染危险因素研究中的混杂偏倚   总被引:3,自引:1,他引:2  
在医院感染危险因素的研究中,有些研究者往往忽视了混杂偏倚的存在,本文选出两篇有关论文就其混杂偏倚问题进行分析,并列出了控制混杂偏倚的几种主要方法,提醒研究者注意预防和控制混杂偏倚  相似文献   

8.
目的探讨二分暴露变量错分对暴露与疾病结局变量联系效应的影响。方法利用错分概率、联系效应以及暴露比例之间的函数,采用R2.0.1软件作图来讨论错分对研究真实性的影响。结果无差异性暴露错分使普通线性模型系数的估计值偏低,当r=0.5时,灵敏度和特异度对错分偏倚产生的影响是相同的,而r≠0.5时,它们对错分偏倚产生的影响是不同的。当错分是无差异性时,暴露比例“趋于0或1,估计的OR值都趋近于1。差异性错分所致的偏倚远比无差异性错分所致的偏倚来得复杂得多,可使OR值趋于或远离无效值。结论暴露错分对暴露与结局变量之间联系效应的影响相当复杂,在研究中对错分偏倚的识别、控制、评估以及正确地对结果进行解释均十分必要。  相似文献   

9.
正1.3偏倚控制医学研究通常是以人为对象,由于人的心理反应和依从性在研究中是难以控制的,而且容易受到外界因素的干扰,因此研究的结果极易出现各种误差,如研究对象回答问题的真实性(是否如实回答问题)、对发生在过去的事件回忆的准确性(时间、数量记忆是否准确)等,如果不真实、不准确将会使研究结果系统地偏离其真实值,这种现象称为偏倚(bias)。偏倚是影响研究质量的重要因素,在研究中不可能做到完全没有偏倚,只有通过周密设计和科学处理尽量减少偏倚。识  相似文献   

10.
目的了解百色市接受抗病毒治疗老年艾滋病患者生存状态及其影响因素。方法采取回顾性动态队列研究,选择2006—2013年百色市接受抗病毒治疗、≥60岁的艾滋病患者为研究对象,收集相关数据,运用寿命表法计算生存率,用Cox比例风险模型分析生存时间的影响因素。结果共有209例接受抗病毒治疗老年艾滋病患者纳入分析,累计观察467.82人年,死亡37例,其中死于艾滋病相关疾病25例,病死率为5.34/100人年。截至观察期末患者抗病毒治疗后的平均生存时间为6.85年,第12、24、36、48、60个月的累积生存率为0.94、0.90、0.84、0.82、0.82。患者治疗前基线血红蛋白、血肌酐和谷草转氨酶,以及是否更换治疗方案与生存时间存在统计学关联。结论治疗基线时低血红蛋白、高谷草转氨酶、高血肌酐水平可缩短接受抗病毒治疗老年艾滋病患者的生存时间,提示在抗病毒治疗前应及时纠正患者的贫血和肝、肾功能,并加强监测随访和及时更换治疗方案,以延长患者的生存时间。  相似文献   

11.
 

目的 了解新型冠状病毒肺炎(COVID-19)患者病房新型冠状病毒(SARS-CoV-2)污染状况。方法 对COVID-19患者病房物体表面以及患者手、护士手套外表面进行涂抹采样,采用逆转录聚合酶链反应(RT-PCR)对涂抹拭子进行SARS-CoV-2核酸检测。结果 47份标本中1份SARS-CoV-2核酸检测阳性,阳性率为2.13%。阳性标本为采样当日SARS-CoV-2核酸检测阳性患者保暖衬衣袖口内表面涂抹拭子,保暖衬衣自患者入院后未曾更换;患者病房高频接触的物体表面如门把手、床档、床头桌、心电监护仪、输液泵等,以及患者手、护士手套外表面等消毒前采集的涂抹拭子SARS-CoV-2核酸检测均阴性。结论 COVID-19患者病房SARS-CoV-2污染程度较低,考虑与病房每日均进行物体表面的清洁消毒,以及强调手卫生有关。患者入院后应更换患者服,患者服应定期更换,有污染时随时更换。

  相似文献   

12.
 目的 探讨院前院内一体化管理对降低急性缺血性脑卒中(AIS)患者误吸及坠积性肺炎发生率的效果。方法 选取2020年3月-2021年10月某院诊治的108例AIS患者,根据干预时间、管理模式不同,将2020年3-12月接受院内常规护理操作的55例AIS患者列为对照组,2021年1-10月接受院前院内一体化管理的53例AIS患者列为干预组,比较两组AIS患者误吸及坠积性肺炎发生率、平均住院时间、患者满意度,以及两组AIS患者的医生和护士感染防控及气道管理知识考核得分、手卫生依从率的差异。结果 干预组AIS患者误吸与坠积性肺炎发生率(分别为9.43%、3.77%)均低于对照组(分别为25.45%、14.55%);干预组平均住院时间短于对照组[(10.79±5.35) d VS (13.69±6.84) d],患者满意度高于对照组(96.23% VS 81.82%),均P<0.05。干预组AIS患者的医生和护士的医院感染防控及气道管理知识考核得分、手卫生依从率均高于对照组(均P<0.001)。结论 运用院前院内一体化管理模式对AIS患者进行早期干预,可降低患者误吸及坠积性肺炎发生率,有效缩短患者住院时间,提升患者满意度,同时还能增强医务人员感染防控意识,提高医院感染防控水平,值得在临床上推广应用。  相似文献   

13.
In randomised controlled trials of treatments for late‐stage cancer, it is common for control arm patients to receive the experimental treatment around the point of disease progression. This treatment switching can dilute the estimated treatment effect on overall survival and impact the assessment of a treatment's benefit on health economic evaluations. The rank‐preserving structural failure time model of Robins and Tsiatis (Comm. Stat., 20 :2609–2631) offers a potential solution to this problem and is typically implemented using the logrank test. However, in the presence of substantial switching, this test can have low power because the hazard ratio is not constant over time. Schoenfeld (Biometrika, 68 :316–319) showed that when the hazard ratio is not constant, weighted versions of the logrank test become optimal. We present a weighted logrank test statistic for the late stage cancer trial context given the treatment switching pattern and working assumptions about the underlying hazard function in the population. Simulations suggest that the weighted approach can lead to large efficiency gains in either an intention‐to‐treat or a causal rank‐preserving structural failure time model analysis compared with the unweighted approach. Furthermore, violation of the working assumptions used in the derivation of the weights only affects the efficiency of the estimates and does not induce bias or inflate the type I error rate. The weighted logrank test statistic should therefore be considered for use as part of a careful secondary, exploratory analysis of trial data affected by substantial treatment switching. ©©2015 The Authors. Statistics inMedicine Published by John Wiley & Sons Ltd.  相似文献   

14.
Surprisingly, survival from a diagnosis of lung cancer has been found to be longer for those who experienced a previous cancer than for those with no previous cancer. A possible explanation is lead‐time bias, which, by advancing the time of diagnosis, apparently extends survival among those with a previous cancer even when they enjoy no real clinical advantage. We propose a discrete parametric model to jointly describe survival in a no‐previous‐cancer group (where, by definition, lead‐time bias cannot exist) and in a previous‐cancer group (where lead‐time bias is possible). We model the lead time with a negative binomial distribution and the post–lead‐time survival with a linear spline on the logit hazard scale, which allows for survival to differ between groups even in the absence of bias; we denote our model Logit‐Spline/Negative Binomial. We fit Logit‐Spline/Negative Binomial to a propensity‐score matched subset of the Surveillance, Epidemiology, and End Results–Medicare linked data set, conducting sensitivity analyses to assess the effects of key assumptions. With lung cancer–specific death as the end point, the estimated mean lead time is roughly 11 months for stage I&II patients; with overall survival, it is roughly 3.4 months in stage I&II. For patients with higher‐stage lung cancers, the mean lead time is 1 month or less for both outcomes. Accounting for lead‐time bias reduces the survival advantage of the previous‐cancer group when one exists, but it does not nullify it in all cases.  相似文献   

15.
Biomarkers that can help identify patients who will have an early clinical benefit from a treatment are important not only for patients' survival and quality of life, but also for the cost of health care. Owing to reasons such as biological variation and limited machine precision, biomarkers are sometimes measured with large errors. Adjusting for the measurement error in calculating the proportion of the treatment effect explained by markers has been a subject of research. The proportion of information gain (PIG), a new quantity to measure the importance of a biomarker, has not yet been studied for variables measured with error. In this article, we provide methods to account for the measurement error in the calculation of PIG for continuous, binary and time‐to‐event outcomes. Simulation shows that the adjusted estimator has little bias and has less variability compared to the naive estimator ignoring the measurement error. Data from an osteoporosis clinical study are used to illustrate the method for a binary outcome. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

16.
In cancer genomic studies, an important objective is to identify prognostic markers associated with patients' survival. Network-based regularization has achieved success in variable selections for high-dimensional cancer genomic data, because of its ability to incorporate the correlations among genomic features. However, as survival time data usually follow skewed distributions, and are contaminated by outliers, network-constrained regularization that does not take the robustness into account leads to false identifications of network structure and biased estimation of patients' survival. In this study, we develop a novel robust network-based variable selection method under the accelerated failure time model. Extensive simulation studies show the advantage of the proposed method over the alternative methods. Two case studies of lung cancer datasets with high-dimensional gene expression measurements demonstrate that the proposed approach has identified markers with important implications.  相似文献   

17.
Research has found a negative association between patient question asking and aspects of their satisfaction. In the context of surgical oncology, the aim of this exploratory study was to test the association between patient question asking and 3 indices of their satisfaction. Participants included 51 women who were newly diagnosed with breast cancer engaged in presurgical consultations with a surgical oncologist from a National Cancer Institute–designated cancer center in the Northeastern United States. Outcomes were patients' postconsultation reports of their satisfaction with the treatment plan, intentions to adhere to the treatment plan, and satisfaction with the surgeon. The main predictor was the frequency of patients' self-initiated questions coded from videotapes of consultations. The frequency of patients' self-initiated questions was negatively associated with their satisfaction with the treatment plan (p = .02), intentions to adhere to the treatment plan (p = .02), and satisfaction with the surgeon (p = .07). Results can be explained in terms of patients' perceptions that the surgeon's information was insufficient or inadequate. Future research needs to identify the specific content of patients' questions and how such content might be associated with satisfaction.  相似文献   

18.
PurposeTo determine whether patients' perception of early therapeutic alliance (TA) could predict time to achieve a target weight among adolescents undergoing treatment for anorexia nervosa.MethodTA was assessed in a prospective cohort recruited from both inpatient and outpatient settings by self-administered and validated questionnaires. Kaplan–Meier survival curves were compared by log rank test, and Cox regression was used to test whether patients' perception of early TA predicted time to achieve a target weight.ResultsIn total, 108 patients were included, and 79.6% achieved a target weight. Better patient perception of early TA increased the hazard ratio (HR) of achieving a target weight (HR = 2.7, 95% confidence interval: 1.7–4.4, p < .001) such as being in the inpatient setting by 6.7. Being very severely underweight at admission decreased the HR of achieving the target weight.ConclusionPatients' perception of early TA is a good predictor of achieving a target weight. Because TA is a modifiable construct, it could be a target for intervention.  相似文献   

19.
目的:调查医联体建设背景下慢病患者就医选择的特征及状况,为了解患者的就医选择、进一步完善医联体建设提供依据,探讨促进医联体发展的政策建议。方法:对北京市某医联体慢病患者进行抽样调查,样本量为781名患者,使用SPSS21.0对数据进行统计分析。结果:慢病患者的就医选择与人口特征、对医联体的感知、患者满意度三个维度存在显著相关。具体来说,患者性别、年龄、受教育程度等倾向特征,收入、医保情况等使能资源,自感病情,评估健康状况,对医联体的认知和体验等方面均显著地影响患者就医选择。结论:医联体建设能够有效影响患者的就医选择,对引导患者合理就医、推进分级诊疗建设起到了切实有效的作用。但是,医联体建设在加强社区医疗卫生机构药物供给、双向转诊和宣传力度等方面仍需加强。  相似文献   

20.
Prognostic studies often estimate survival curves for patients with different covariate vectors, but the validity of their results depends largely on the accuracy of the estimated covariate effects. To avoid conventional proportional hazards and linearity assumptions, flexible extensions of Cox's proportional hazards model incorporate non‐linear (NL) and/or time‐dependent (TD) covariate effects. However, their impact on survival curves estimation is unclear. Our primary goal is to develop and validate a flexible method for estimating individual patients' survival curves, conditional on multiple predictors with possibly NL and/or TD effects. We first obtain maximum partial likelihood estimates of NL and TD effects and use backward elimination to select statistically significant effects into a final multivariable model. We then plug the selected NL and TD estimates in the full likelihood function and estimate the baseline hazard function and the resulting survival curves, conditional on individual covariate vectors. The TD and NL functions and the log hazard are modeled with unpenalized regression B‐splines. In simulations, our flexible survival curve estimates were unbiased and had much lower mean square errors than the conventional estimates. In real‐life analyses of mortality after a septic shock, our model improved significantly the deviance (likelihood ratio test = 84.8, df = 20, p < 0.0001) and changed substantially the predicted survival for several subjects. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

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