Six minute walk test inter-rater reproducibility in COPD patients: Cross-sectional study

Introduction: Six minute walk test (6MWT) is an important tool in the evaluation of functional capacity and prognostic in COPD patients. However, especially in long term follow-up, this test could be executed by different evaluators and it isn’t well-know if 6MWT has an acceptable inter-rater reproducibility. Aims: This study analyzed 6MWT intra and inter-rater reproducibility in COPD patients. Methods: In this study, 31 patients with clinical and spirometrical diagnosis of COPD were enrolled to participate. They performed three 6MWT (American Thoracic Society, AJRCCM 2002; 116: 111–7), the first and second were executed by the same evaluator with a 30min interval, and the last by a different evaluator a week later. Exercise capacity was determinate using the walking distance. Intraclass correlation coefficient (ICC), Bland-Altmann plots were used. Results: Intra and inter-rater relative reproducibility was excellent (ICC>0,8). Limits of agreement (Figura 1) were higher than the minimal important clinical difference (35m) in both intra and inter-rater analysis. Figure 1: Reproducibility A: Intra-rater; B: Inter-rater. 6MWT: Six minute walk test. In spite of the excellent relative reproducibility, the high bias reaffirms the need of a practice test, and the caution in a comparison of tests done by two different evaluators. Conclusions: 6MWT don’t have an acceptable inter-rater reproducibility, due to its high bias.