Dept of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA.
Eur Respir J. 2011 Apr;37(4):784-90. doi: 10.1183/09031936.00063810. Epub 2010 Aug 6.
Our aim was to determine the minimal important difference (MID) for 6-min walk distance (6MWD) and maximal cycle exercise capacity (MCEC) in patients with severe chronic obstructive pulmonary disease (COPD). 1,218 patients enrolled in the National Emphysema Treatment Trial completed exercise tests before and after 4-6 weeks of pre-trial rehabilitation, and 6 months after randomisation to surgery or medical care. The St George's Respiratory Questionnaire (domain and total scores) and University of California San Diego Shortness of Breath Questionnaire (total score) served as anchors for anchor-based MID estimates. In order to calculate distribution-based estimates, we used the standard error of measurement, Cohen's effect size and the empirical rule effect size. Anchor-based estimates for the 6MWD were 18.9 m (95% CI 18.1-20.1 m), 24.2 m (95% CI 23.4-25.4 m), 24.6 m (95% CI 23.4-25.7 m) and 26.4 m (95% CI 25.4-27.4 m), which were similar to distribution-based MID estimates of 25.7, 26.8 and 30.6 m. For MCEC, anchor-based estimates for the MID were 2.2 W (95% CI 2.0-2.4 W), 3.2 W (95% CI 3.0-3.4 W), 3.2 W (95% CI 3.0-3.4 W) and 3.3 W (95% CI 3.0-3.5 W), while distribution-based estimates were 5.3 and 5.5 W. We suggest a MID of 26 ± 2 m for 6MWD and 4 ± 1 W for MCEC for patients with severe COPD.
我们的目的是确定严重慢性阻塞性肺疾病（COPD）患者 6 分钟步行距离（6MWD）和最大循环运动能力（MCEC）的最小有意义差异（MID）。1218 名参加国家肺气肿治疗试验的患者在术前康复 4-6 周前后以及随机分配至手术或医疗护理后 6 个月完成了运动测试。圣乔治呼吸问卷（领域和总分）和加利福尼亚大学圣地亚哥短气问卷（总分）作为锚定基于锚的 MID 估计的依据。为了计算基于分布的估计，我们使用测量的标准误差、Cohen 的效应大小和经验法则效应大小。6MWD 的基于锚的估计值为 18.9m（95%CI18.1-20.1m）、24.2m（95%CI23.4-25.4m）、24.6m（95%CI23.4-25.7m）和 26.4m（95%CI25.4-27.4m），与基于分布的 MID 估计值 25.7、26.8 和 30.6m 相似。对于 MCEC，MID 的基于锚的估计值为 2.2W（95%CI2.0-2.4W）、3.2W（95%CI3.0-3.4W）、3.2W（95%CI3.0-3.4W）和 3.3W（95%CI3.0-3.5W），而基于分布的估计值为 5.3 和 5.5W。我们建议严重 COPD 患者的 6MWD 的 MID 为 26±2m，MCEC 的 MID 为 4±1W。
