INSERM, U738, Paris, France.
BMJ Open. 2013 Aug 23;3(8):e003342. doi: 10.1136/bmjopen-2013-003342.
We examined how assessments of risk of bias of primary studies are carried out and incorporated into the statistical analysis and overall findings of a systematic review.
A cross-sectional review.
We assessed 200 systematic reviews of randomised trials published between January and March 2012; Cochrane (n=100), non-Cochrane (Database of Reviews of Effects) (n=100).
Our primary outcome was a descriptive analysis of how assessments of risk of bias are carried out, the methods used, and the extent to which such assessments were incorporated into the statistical analysis and overall review findings.
While Cochrane reviews routinely reported the method of risk of bias assessment and presented their results either in text or table format, 20% of non-Cochrane reviews failed to report the method used and 39% did not present the assessment results. Where it was possible to evaluate the individual results of the risk of bias assessment (n=154), 75% (n=116/154) of reviews had ≥1 trial at high risk of bias; the median proportion of trials per review at high risk of bias was 50% (IQR 31% to 89%). Despite this, only 56% (n=65/116) incorporated the risk of bias assessment into the interpretation of the results in the abstract and 41% (n=47/116) (49%; n=40/81 Cochrane and 20%; n=7/35 non-Cochrane) incorporated the risk of bias assessment into the interpretation of the conclusions. Of the 83% (n=166/200) systematic reviews which included a meta-analysis, only 11% (n=19/166) incorporated the risk of bias assessment into the statistical analysis.
Cochrane reviews were more likely than non-Cochrane reviews to report how risk of bias assessments of primary studies were carried out; however, both frequently failed to take such assessments into account in the statistical analysis and conclusions of the systematic review.
我们考察了如何对原始研究的偏倚风险进行评估，并将其纳入系统评价的统计分析和总体结果中。
横断面研究。
我们评估了 2012 年 1 月至 3 月间发表的 200 项随机试验系统评价；Cochrane（n=100），非 Cochrane（效应评价数据库）（n=100）。
我们的主要结局是对偏倚风险评估的实施情况、使用的方法以及评估结果在多大程度上纳入统计分析和系统评价结果进行描述性分析。
虽然 Cochrane 综述通常会报告偏倚风险评估方法，并以文本或表格形式呈现结果，但 20%的非 Cochrane 综述未报告使用的方法，39%的综述未呈现评估结果。在可以评估偏倚风险评估个体结果的情况下（n=154），75%（n=116/154）的综述中有≥1项试验存在高偏倚风险；每项综述中处于高偏倚风险的试验中位数比例为 50%（IQR 31%~89%）。尽管如此，只有 56%（n=65/116）在摘要中结合了偏倚风险评估来解释结果，41%（n=47/116）（49%；n=40/81 Cochrane 和 20%；n=7/35 非 Cochrane）在结论中结合了偏倚风险评估来解释结论。在纳入荟萃分析的 83%（n=166/200）系统评价中，只有 11%（n=19/166）将偏倚风险评估纳入了统计分析。
Cochrane 综述比非 Cochrane 综述更有可能报告如何对原始研究的偏倚风险进行评估；然而，两者都经常未能在系统评价的统计分析和结论中考虑这些评估。
