Papanikolaou Panagiotis N, Christidi Georgia D, Ioannidis John P A
Clinical Trials and Evidence-Based Medicine Unit, Department of Hygiene and Epidemiology, University of Ioannina School of Medicine, Ioannina, Greece.
CMAJ. 2006 Feb 28;174(5):635-41. doi: 10.1503/cmaj.050873.
Information on major harms of medical interventions comes primarily from epidemiologic studies performed after licensing and marketing. Comparison with data from large-scale randomized trials is occasionally feasible. We compared evidence from randomized trials with that from epidemiologic studies to determine whether they give different estimates of risk for important harms of medical interventions.
We targeted well-defined, specific harms of various medical interventions for which data were already available from large-scale randomized trials (> 4000 subjects). Nonrandomized studies involving at least 4000 subjects addressing these same harms were retrieved through a search of MEDLINE. We compared the relative risks and absolute risk differences for specific harms in the randomized and nonrandomized studies.
Eligible nonrandomized studies were found for 15 harms for which data were available from randomized trials addressing the same harms. Comparisons of relative risks between the study types were feasible for 13 of the 15 topics, and of absolute risk differences for 8 topics. The estimated increase in relative risk differed more than 2-fold between the randomized and nonrandomized studies for 7 (54%) of the 13 topics; the estimated increase in absolute risk differed more than 2-fold for 5 (62%) of the 8 topics. There was no clear predilection for randomized or nonrandomized studies to estimate greater relative risks, but usually (75% [6/8]) the randomized trials estimated larger absolute excess risks of harm than the nonrandomized studies did.
Nonrandomized studies are often conservative in estimating absolute risks of harms. It would be useful to compare and scrutinize the evidence on harms obtained from both randomized and nonrandomized studies.
关于医学干预主要危害的信息主要来自于许可和上市后进行的流行病学研究。偶尔也可以与大规模随机试验的数据进行比较。我们比较了随机试验和流行病学研究的证据，以确定它们对医学干预重要危害的风险估计是否不同。
我们针对各种医学干预明确界定的特定危害，这些危害已有大规模随机试验（>4000名受试者）的数据。通过检索MEDLINE检索涉及至少4000名受试者且针对这些相同危害的非随机研究。我们比较了随机和非随机研究中特定危害的相对风险和绝对风险差异。
对于15种危害，找到了符合条件的非随机研究，针对这些危害已有随机试验的数据。在15个主题中的13个主题中，研究类型之间相对风险的比较是可行的，在8个主题中绝对风险差异的比较是可行的。在13个主题中的7个（54%）中，随机和非随机研究之间估计的相对风险增加差异超过2倍；在8个主题中的5个（62%）中，估计的绝对风险增加差异超过2倍。在估计更大的相对风险方面，随机或非随机研究没有明显的偏好，但通常（75%[6/8]）随机试验估计的危害绝对超额风险比非随机研究更大。
非随机研究在估计危害的绝对风险时往往较为保守。比较和仔细审查从随机和非随机研究中获得的危害证据将是有用的。
