Reliability, repeatability and sensitivity to change of externally and self-paced walking tests in COPD patients

Abstract

In COPD, several walking tests have been proposed to measure exercise tolerance but their relative merits are uncertain. We studied 57 moderate-to-severe, stable COPD patients (mean FEV1 35 +/- 12% predicted). Within a 2-month period, we compared reliability (inter-subject variability) and repeatability (intra-subject variability) of the most widely used 6-min walks (6MWD), with self-paced 2-min walks (2MWD) and externally paced, incremental shuttles (Shuttle). On 9 separate days either of the three 6MWD, 2MWD or Shuttles were performed (nine walks of each type). Then, each walk was performed before and after bronchodilators (BD) to assess sensitivity to change (mean change/standard deviation of change (sensitivity index--SI)). For all exercise tests, reliability was >90% (2MWD 95%, 6MWD 92% and Shuttle 91%). Repeatability was excellent (overall <10% intra-subject variation; for 2MWD 5%, 6MWD 8% and Shuttle 9%). On average, the first walking distance was significantly shorter, but there were no significant differences between second and third walks. Dyspnoea scores were much less reproducible. BD produced highly significant improvements in Shuttle (pre-BD 27 SD=11 --> post-BD 30 SD=11), 6MWD (424 m SD=115 --> 462 m SD=106) and 2MWD (153 m SD=35 --> 162 m SD=34), (P < 0.0001). SI was similar for all walks (6MWD 0.84, 2MWD 0.75 and Shuttle 0.76). In moderate-to-severe COPD, 2MWDs are as informative as 6MWDs without their disadvantages. Self-paced walks are as useful as externally paced Shuttles.

Reference Equation for the 2-Minute Walk Test in Adults and the Elderly

“…Therefore, subjects presented with reduced functional capacity not only because of the low values in relation to the percentage of predicted but also because the DW was lower than the lower limit of the normal range (121 vs 152 m for amputees, 140.7 vs 165 m for out-patient transtibial amputees, 130.8 vs 145 m for COPD patients, and 136 vs 155 m for cardiac surgery patients). Considering the responsiveness of the 2MWT, a study 5 has shown that patients with COPD (n ϭ 57; 30 males; 69 y old; FEV 1 ϭ 35 Ϯ 12% of predicted) walked 153 and 162 m in the 2MWT before and after use of a bronchodilator, respectively, corresponding to 79.7% and 84.4% of the predicted values obtained from our prediction equation, considering male subjects. In addition to the improvement in terms of absolute values (9 m), DW reached values Ͼ 80% of the predicted values after use of a bronchodilator.…”

“…3 Despite the limitations assigned to the 2MWT for patients with COPD, it has been incorporated again for use in this population and has proved to be valid for the assessment of exercise capacity and sensitive for detecting re-sponse to interventions in moderate-to-severe patients. 4,5 The 2MWT has also been used in lower limb amputations, 6,7 the elderly, 8 neuromuscular diseases, 9,10 and chronic heart diseases. 11 However, no reference values have been established for the 2MWT, making it impossible to assess properly whether there is reduced functional capacity when performing this test.…”

Reproducibility of 6-minute walking test in patients with COPD

“…In general, the 6MWT is a reliable test in COPD patients but a learning effect has been suggested [10][11][12][13][14][15], i.e. patients achieving a considerably higher walked distance when a second test is performed.…”

Prospective validation of the endurance shuttle walking test in the context of bronchodilation in COPD

“…This study procedure is at variance with the suggestion that two ISWTs should be performed to account for a small but significant learning effect seen with this test [31][32][33][34][35][36][37]. This proposed methodology is likely to be important to accurately determine ISWT performance.…”