Bucher H C, Guyatt G H, Griffith L E, Walter S D
Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada.
J Clin Epidemiol. 1997 Jun;50(6):683-91. doi: 10.1016/s0895-4356(97)00049-8.
When little or no data directly comparing two treatments are available, investigators often rely on indirect comparisons from studies testing the treatments against a control or placebo. One approach to indirect comparison is to pool findings from the active treatment arms of the original controlled trials. This approach offers no advantage over a comparison of observational study data and is prone to bias. We present an alternative model that evaluates the differences between treatment and placebo in two sets of clinical trials, and preserves the randomization of the originally assigned patient groups. We apply the method to data on sulphamethoxazole-trimethoprim or dapsone/pyrimethamine as prophylaxis against Pneumocystis carinii in HIV infected patients. The indirect comparison showed substantial increased benefit from the former (odds ratio 0.37, 95% CI 0.21 to 0.65), while direct comparisons from randomized trials suggests a much smaller difference (risk ratio 0.64, 95% CI 0.45 to 0.90; p-value for difference of effect = 0.11). Direct comparisons of treatments should be sought. When direct comparisons are unavailable, indirect comparison meta-analysis should evaluate the magnitude of treatment effects across studies, recognizing the limited strength of inference.
当几乎没有或根本没有直接比较两种治疗方法的数据时，研究人员通常依赖于针对对照或安慰剂测试治疗方法的研究进行间接比较。间接比较的一种方法是汇总原始对照试验中活性治疗组的研究结果。这种方法与观察性研究数据的比较相比没有优势，并且容易产生偏差。我们提出了一种替代模型，该模型评估两组临床试验中治疗与安慰剂之间的差异，并保留最初分配患者组的随机化。我们将该方法应用于关于磺胺甲恶唑 - 甲氧苄啶或氨苯砜/乙胺嘧啶预防HIV感染患者卡氏肺孢子虫的数据。间接比较显示前者的益处大幅增加（优势比0.37，95%可信区间0.21至0.65），而随机试验的直接比较表明差异要小得多（风险比0.64，95%可信区间0.45至0.90；效应差异的p值 = 0.11）。应寻求治疗方法的直接比较。当无法进行直接比较时，间接比较荟萃分析应评估各项研究中治疗效果的大小，同时认识到推断的强度有限。
