GRADE guidelines: 4. Rating the quality of evidence-study limitations (risk of bias)
GRADE guidelines: 4. Rating the quality of evidence-study limitations (risk of bias)
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DOI：
10.1016/j.jclinepi.2010.07.017
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发表时间：
2011-04-01
影响因子：
7.2
通讯作者：
Schuenemann, Holger J.
中科院分区：
文献类型：
--
作者：
Guyatt, Gordon H.;Oxman, Andrew D.;Schuenemann, Holger J.
在GRADE方法中，随机试验开始时是高质量的证据，观察性研究是低质量的证据，但如果大多数相关证据来自具有高偏倚风险的研究，则两者都可以被降级。随机试验的公认局限性包括未能隐藏分配、未能设盲、失访以及未能适当考虑意向治疗原则。最近认识到的局限性包括为了明显的益处而及早停止，以及根据结果选择性地报告结果。观察性研究的主要局限性包括使用不适当的对照和未能充分调整预后不平衡。偏倚风险可能因结果而异（例如，全因死亡率的失访率可能远低于生活质量的失访率），这是许多系统性综述忽略的一个考虑因素。在决定是否降低随机试验或观察性研究的偏倚风险时，作者不应采用跨研究平均的方法。相反，对于任何个体结局，当存在一些高风险研究和一些低风险偏倚研究时，他们应考虑仅纳入偏倚风险较低的研究。(C)2011 Elsevier Inc. All rights reserved.
In the GRADE approach, randomized trials start as high-quality evidence and observational studies as low-quality evidence, but both can be rated down if most of the relevant evidence comes from studies that suffer from a high risk of bias. Well-established limitations of randomized trials include failure to conceal allocation, failure to blind, loss to follow-up, and failure to appropriately consider the intention-to-treat principle. More recently recognized limitations include stopping early for apparent benefit and selective reporting of outcomes according to the results. Key limitations of observational studies include use of inappropriate controls and failure to adequately adjust for prognostic imbalance. Risk of bias may vary across outcomes (e.g., loss to follow-up may be far less for all-cause mortality than for quality of life), a consideration that many systematic reviews ignore. In deciding whether to rate down for risk of bias whether for randomized trials or observational studies-authors should not take an approach that averages across studies. Rather, for any individual outcome, when there are some studies with a high risk, and some with a low risk of bias, they should consider including only the studies with a lower risk of bias. (C) 2011 Elsevier Inc. All rights reserved.