热度 107|
MMRM (六)
上两篇博文,小胖介绍了observed case anlaysis、LOCF和MMRM处理缺失值方法的不同,由于其处理缺失值方法的不同,有时会导致结果的大不同,下边我们来看一个这方面的实例:
Pollack MH,et al.The selective GABA reuptake inhibitor tiagabine for the treatment of generalized anxiety disorder: results of a placebo-controlled study.J Clin Psychiatry. 2005 Nov;66(11):1401-8.
这是一项评价selective GABA reuptake inhibitor tiagabine治疗成年广泛性焦虑障碍的为期8周的随机双盲安慰剂对照研究。本研究的主要终点是the change from baseline in HAMA total score to final visit。
Result:
A total of 266 patients (tiagabine, N = 134; placebo, N = 132) were included in safety analyses; 260 patients (tiagabine N = 130; placebo N = 130) were included in efficacy analyses. Tiagabine reduced symptoms of GAD according to the observed case and mixed models repeated-measures (MMRM) analyses but not the primary last-observation-carried-forward (LOCF) analysis.
Conclusion:
The primary LOCF analysis was negative; however, results from the observed case and MMRM analyses suggest that tiagabine may be a useful treatment option for adult patients diagnosed with GAD. These findings warrant further evaluation in randomized clinical studies.
从上边这个临床试验的实例中,我们可以看出,试验共进行了三种分析即observed case、LOCF和MMRM分析,然而却出现了不同的结论,LOCF分析的结果是阴性的,而observed case和MMRM分析的结果却是阳性的,怎么来解释呢?
我们来看一下病人入组和完成试验的情况,下边是本试验的patient disposition情况:
(1) 对于observed case分析来说,纳入主要终点分析的病人为两组完成试验的病人数即97+100=197
(2) 对于LOCF分析来说,纳入主要终点分析的病人为130+130=260,但两组经过LOCF结转的病人分别为130-97=33例以及130-100=30例,共63例
(3) 对于MMRM来说,纳入主要终点分析的病人为130+130=260,并且这260例病人没有一例病人是结转的
从patient disposition情况来看,其drop out是比较高的,因此经LOCF结转的病例也会比较多,这就为三种分析最后出现不同的结果埋下了伏笔。。。
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