Reproducibility of cadence-free 6-minute step test in subjects with COPD

• Published in: Respiratory care Vol. 59; no. 4; p. 538
• Main Authors: da Costa, Joyce Nf, Arcuri, Juliano F, Gonçalves, Ivana L, Davi, Simone F, Pessoa, Bruna V, Jamami, Mauricio, Di Lorenzo, Valéria Ap
• Format: Journal Article
• Language: English
• Published: United States 01.04.2014
• Subjects: Aged; Analysis of Variance; Cross-Sectional Studies; Exercise Test - methods; Exercise Tolerance - physiology; Humans; Prospective Studies; Pulmonary Disease, Chronic Obstructive - physiopathology; Reproducibility of Results; exercise test; reproducibility; COPD; chronic obstructive pulmonary disease
• ISSN: 1943-3654
• DOI: 10.4187/respcare.02743

Six-minute step test (6MST) has been used to assess functional capacity in chronic conditions; however, its reproducibility in the COPD population has not been evaluated. Our study objective was to evaluate 6MST reproducibility. The test was performed in a single 20-cm height step, and subjects were instructed to step up and down (cadence-free) for 6 min. Subjects underwent three tests. The first and second were controlled by the same assessor with a 30-min interval. The third test was controlled by a different assessor one week later. For intra-rater comparison, the first and second performances of the test were used, and for inter-assessor comparison, the better performance of the first two tests was compared with the third test. Excellent intra-rater and inter-rater relative reproducibility was observed (intraclass correlation coefficient > 0.8), and there was no statistical difference (repeated measures of analysis of variance) among the performances of the three tests. Intra-rater error values were acceptable (mean error of 5.7 steps and limits of agreement between -7 and 18 steps). Inter-rater error values were not acceptable (mean error of 4.4 steps and limits of agreement between -20 and 29 steps. 6MST proved to be reproducible in the COPD population when performed by the same assessor.