National Heart & Lung Institute, Imperial College, London, United Kingdom.
Am J Respir Crit Care Med. 2011 May 1;183(9):1231-7. doi: 10.1164/rccm.201007-1179OC. Epub 2010 Dec 3.
The 6-minute-walk test (6MWT) is a practical and clinically meaningful measure of exercise tolerance with favorable performance characteristics in various cardiac and pulmonary diseases. Performance characteristics in patients with idiopathic pulmonary fibrosis (IPF) have not been systematically evaluated.
To assess the reliability, validity, and responsiveness of the 6MWT and estimate the minimal clinically important difference (MCID) in patients with IPF.
The study population included all subjects completing a 6MWT in a clinical trial evaluating interferon gamma-1b (n = 822). Six-minute walk distance (6MWD) and other parameters were measured at baseline and at 24-week intervals using a standardized protocol. Parametric and distribution-independent correlation coefficients were used to assess the strength of the relationships between 6MWD and measures of pulmonary function, dyspnea, and health-related quality of life. Both distribution-based and anchor-based methods were used to estimate the MCID.
Comparison of two proximal measures of 6MWD (mean interval, 24 d) demonstrated good reliability (coefficient = 0.83; P < 0.001). 6MWD was weakly correlated with measures of physiologic function and health-related quality of life; however, values were consistently and significantly lower for patients with the poorest functional status, suggesting good construct validity. Importantly, change in 6MWD was highly predictive of mortality; a 24-week decline of greater than 50 m was associated with a fourfold increase in risk of death at 1 year (hazard ratio, 4.27; 95% confidence interval, 2.57- 7.10; P < 0.001). The estimated MCID was 24-45 m.
The 6MWT is a reliable, valid, and responsive measure of disease status and a valid endpoint for clinical trials in IPF.
6 分钟步行测试（6MWT）是一种实用且具有临床意义的运动耐量测量方法，在各种心脏和肺部疾病中具有良好的性能特征。特发性肺纤维化（IPF）患者的性能特征尚未得到系统评估。
评估 6MWT 的可靠性、有效性和反应性，并估计 IPF 患者的最小临床重要差异（MCID）。
研究人群包括在评估干扰素 γ-1b 的临床试验中完成 6MWT 的所有受试者（n=822）。使用标准化方案在基线和 24 周间隔测量 6 分钟步行距离（6MWD）和其他参数。使用参数和非分布依赖相关系数评估 6MWD 与肺功能、呼吸困难和健康相关生活质量测量值之间的关系强度。使用基于分布和基于锚的方法来估计 MCID。
对 6MWD 的两个近端测量值（平均间隔 24 天）的比较表明具有良好的可靠性（系数=0.83；P<0.001）。6MWD 与生理功能和健康相关生活质量的测量值弱相关；然而，对于功能状态最差的患者，值始终显著较低，表明具有良好的结构有效性。重要的是，6MWD 的变化高度预测死亡率；24 周内下降大于 50 米与 1 年内死亡风险增加四倍相关（风险比，4.27；95%置信区间，2.57-7.10；P<0.001）。估计的 MCID 为 24-45 米。
6MWT 是疾病状态的可靠、有效和敏感的测量方法，也是 IPF 临床试验的有效终点。
