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急求！！cochrane质量评价工具关于生存数据的失访偏倚 attrition bias如何评价
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cochrane手册上是这样描述的：“For studies reporting time-to-event data, all participants who did not experience the event of interest are considered to be ‘censored’ on the date of their last follow-up (we do not know whether the outcome event occurred after follow-up ended). The important consideration for this type of analysis is whether such censoring can be assumed to be unbiased, i.e. that the intervention effect (e.g. assessed by a hazard ratio) in individuals who were censored before the scheduled end of follow-up is the same as the hazard ratio in other individuals. In other words, there is no bias if censoring is unrelated to prognosis.”“low risk：Reasons for missing outcome data unlikely to be related to true outcome (for survival data, censoring unlikely to be introducing bias)“不知道具体如何评价，是否是看删失censored数据在样本量中的比例来决定风险高低？
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高lnyx cochrane手册上是这样描述的：“For studies reporting time-to-event data, all participants who did not experience the event of interest are considered to be ‘censored’ on the date of their last follow-up (we do not know whether the outcome event occurred after follow-up ended). The important consideration for this type of analysis is whether such censoring can be assumed to be unbiased, i.e. that the intervention effect (e.g. assessed by a hazard ratio) in individuals who were censored before the scheduled end of follow-up is the same as the hazard ratio in other individuals. In other words, there is no bias if censoring is unrelated to prognosis.”“low risk：Reasons for missing outcome data unlikely to be related to true outcome (for survival data, censoring unlikely to be introducing bias)“不知道具体如何评价，是否是看删失censored数据在样本量中的比例来决定风险高低？The important consideration for this type of analysis is whether such censoring can be assumed to be unbiased, i.e. that the intervention effect (e.g. assessed by a hazard ratio) in individuals who were censored before the scheduled end of followup is the same as the hazard ratio in other individuals. In other words, there is no bias if censoring is unrelated to prognosis.”我觉得讲得挺清楚啊...删失指的是那些还没有出现结局便离开试验的受试者，对于他们的time to event，我们假设在试验的最后一次follow-up的时间他们出现了结局。然而，因为我们不知道他们的结局到底还有多久才会出现，此时结果是删失的。是否偏倚主要考虑删失是否引起偏倚：只要删失与预后（临床结局）无关，那么就没有偏倚。例如，可以对比在计划随访时间前删失的受试者（完成试验前离开了试验，没出现结局）的干预效果与其他未删失的受试者干预的疗效结局是否一致。一致的话，说明这种删失对预后没有影响，有的话，说明有影响?最后解释了survival data，删失不会引起bias。我觉得是指那种完成试验后，但是受试者都没出现结局（死亡）的这种删失吧? 这种删失不引起偏倚。
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givan The important consideration for this type of analysis is whether such censoring can be assumed to be unbiased, i.e. that the intervention effect (e.g. assessed by a hazard ratio) in individuals who were censored before the scheduled end of followup is the same as the hazard ratio in other individuals. In other words, there is no bias if censoring is unrelated to prognosis.”我觉得讲得挺清楚啊...删失指的是那些还没有出现结局便离开试验的受试者，对于他们的time to event，我们假设在试验的最后一次follow-up的时间他们出现了结局。然而，因为我们不知道他们的结局到底还有多久才会出现，此时结果是删失的。是否偏倚主要考虑删失是否引起偏倚：只要删失与预后（临床结局）无关，那么就没有偏倚。例如，可以对比在计划随访时间前删失的受试者（完成试验前离开了试验，没出现结局）的干预效果与其他未删失的受试者干预的疗效结局是否一致。一致的话，说明这种删失对预后没有影响，有的话，说明有影响?最后解释了survival data，删失不会引起bias。我觉得是指那种完成试验后，但是受试者都没出现结局（死亡）的这种删失吧? 这种删失不引起偏倚。一般rct试验中用了itt分析得到了os和pfs的hr，那么具体要如何计算删失的受试者的干预效果和未删失的受试者的干预效果呢？
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高lnyx 一般rct试验中用了itt分析得到了os和pfs的hr，那么具体要如何计算删失的受试者的干预效果和未删失的受试者的干预效果呢？我也不大懂，只能给点看法。我觉得一般做得好的rct给出itt的同时也可能会提供pp。pp不就是未删失的受试者嘛（或者说仅试验结束后的删失），拿它们与itt对比？itt就是包括试验前删失和试验后删失的了。
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