The impact of study size on meta-analyses: examination of underpowered studies in Cochrane reviews.
The impact of study size on meta-analyses: examination of underpowered studies in Cochrane reviews.
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DOI：
10.1371/journal.pone.0059202
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发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
Higgins JP
中科院分区：
文献类型：
--
作者：
Turner RM;Bird SM;Higgins JP
大多数荟萃分析包括来自一个或多个小型研究的数据，这些研究单独没有能力检测干预效果。在已发表的荟萃分析中，充分支持和不足支持的研究的相对影响尚未被探讨。我们检查了Cochrane综述中发表的荟萃分析中可用研究的功率分布，并调查了功率不足的研究对荟萃分析结果的影响。对于1991篇Cochrane综述的14886篇二元结果的meta分析，我们计算了每个meta分析中每个研究的威力。我们将足够的功率定义为≥50%的功率来检测30%的相对风险降低。在1107项荟萃分析的子集中，包括5项或更多的研究，其中至少有两项充分支持和至少一项支持不足，将结果与缺乏支持的研究进行比较。在14886项荟萃分析中，有10492项（70%）纳入的研究均存在效力不足；只有2588篇（17%）纳入了至少两项充分有力的研究。34%的荟萃分析本身得到了充分的支持。在所有荟萃分析中，总相对风险的中位数为0.75（四分位数间范围为0.55至0.89）。在所检查的子集中，对照药理学试验的荟萃分析中，效力不足的研究的优势比比充分效力的研究低15% (95% CI为11%至18%，P<0.0001)；在对照非药物试验的荟萃分析中，降低了12% （95% CI 7% ~ 17%， P<0.0001）。当忽略弱效研究时，干预效果的标准误差中位数增加11%（四分位数间范围为- 1%至35%）；研究间异质性趋于降低。当Cochrane综述报告的荟萃分析中至少有两项足够有力的研究时，缺乏有力的研究通常提供的信息很少，如果需要对证据进行快速审查，可能会被忽略。然而，在大多数Cochrane综述中，证据不足的研究构成了全部证据。
Most meta-analyses include data from one or more small studies that, individually, do not have power to detect an intervention effect. The relative influence of adequately powered and underpowered studies in published meta-analyses has not previously been explored. We examine the distribution of power available in studies within meta-analyses published in Cochrane reviews, and investigate the impact of underpowered studies on meta-analysis results. For 14,886 meta-analyses of binary outcomes from 1,991 Cochrane reviews, we calculated power per study within each meta-analysis. We defined adequate power as ≥50% power to detect a 30% relative risk reduction. In a subset of 1,107 meta-analyses including 5 or more studies with at least two adequately powered and at least one underpowered, results were compared with and without underpowered studies. In 10,492 (70%) of 14,886 meta-analyses, all included studies were underpowered; only 2,588 (17%) included at least two adequately powered studies. 34% of the meta-analyses themselves were adequately powered. The median of summary relative risks was 0.75 across all meta-analyses (inter-quartile range 0.55 to 0.89). In the subset examined, odds ratios in underpowered studies were 15% lower (95% CI 11% to 18%, P<0.0001) than in adequately powered studies, in meta-analyses of controlled pharmacological trials; and 12% lower (95% CI 7% to 17%, P<0.0001) in meta-analyses of controlled non-pharmacological trials. The standard error of the intervention effect increased by a median of 11% (inter-quartile range −1% to 35%) when underpowered studies were omitted; and between-study heterogeneity tended to decrease. When at least two adequately powered studies are available in meta-analyses reported by Cochrane reviews, underpowered studies often contribute little information, and could be left out if a rapid review of the evidence is required. However, underpowered studies made up the entirety of the evidence in most Cochrane reviews.
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DOI：
10.1111/j.1467-985x.2008.00547.x
发表时间：
2009-01
期刊：
Journal of the Royal Statistical Society. Series A, (Statistics in Society)
影响因子：
--
作者：
Turner RM;Spiegelhalter DJ;Smith GC;Thompson SG
通讯作者：
Thompson SG
在系统评价的时代，单个试验的规模仍然很重要。
影响因子：
15.8
作者：
Guyatt, Gordon H.;Mills, Edward J.;Elbourne, Diana
通讯作者：
Elbourne, Diana
DOI：
10.1016/0197-2456(86)90046-2
发表时间：
1986-09-01
期刊：
CONTROLLED CLINICAL TRIALS
影响因子：
--
作者：
DERSIMONIAN, R;LAIRD, N
通讯作者：
LAIRD, N
影响因子：
4
作者：
Moreno SG;Sutton AJ;Ades AE;Stanley TD;Abrams KR;Peters JL;Cooper NJ
通讯作者：
Cooper NJ
影响因子：
1.7
作者：
Ruecker, Gerta;Carpenter, James R.;Schwarzer, Guido
通讯作者：
Schwarzer, Guido