Between-day reliability of a novel incremental step test to assess exercise capacity in COPD patients

Abstract

<b>Introduction:</b> Most step tests applied to COPD patients were originally designed for healthy subjects or have self-paced performance aims. A novel incremental step test was developed specifically for COPD patients based on the Chester step test and the incremental shuttle walk test. <b>Objectives:</b> To analyze the between-day reliability of this incremental step test (IST) in stable COPD patients. <b>Methods:</b> In a cross-sectional study, patients performed the IST twice on two occasions (separated by 7 days) to establish reliability (number of steps and total test time), measured using the intraclass correlation coefficient – ICC2,1. Before and immediately after the tests, heart rate (HR), dyspnea, leg fatigue, and SpO2 were measured. Wilcoxon Signed-Rank test was used to determine whether there were differences between tests in performance, HR, dyspnea, leg fatigue, and SpO2. <b>Results:</b> 18 COPD patients (age: 68.3±6.6; FEV1(%): 58.4±14.5) were enrolled. Excellent reliability was found for number of steps (ICC=0.94) and total test time (ICC=0.91). No significant differences were found between tests in number of steps (test 1: 58.50 [32.50; 79.50] vs. test 2: 77.50 [44.50; 91.00] steps) and test total time (test 1: 265.50 [166.25; 337.00] vs. test 2: 330.00 [219.50;370.75] sec). No significant differences were found on HR, dyspnea, leg fatigue, and SpO2 before and immediately after the tests. <b>Conclusion:</b> We demonstrate that our novel incremental step test is reproducible in COPD patients. However, additional studies are required to suggest that only one test is enough to assess exercise capacity.