Construct validity and reliability of the 2-Minute Step Test (2MST) in individuals with low back pain

Abstract

BackgroundFunctional tests are important clinical tools, since they are non-invasive methods, with simple applicability, and low cost. However, there are few tests adapted for individuals with chronic low back pain. Thus, our objective was to evaluate the test-retest and inter-rater reliability of the 2-Minute Step Test in individuals with chronic low back pain and to correlate the test score with measures of pain and physical activity.MethodsWe included patients aged between 18 and 45 years, of both sexes, and with low back pain. The interval between the test and retest was 7 days. We analyzed the data via intra-class correlation coefficient (ICC), confidence interval at 95%, standard error of measurement, and minimum detectable change for reliability. We used the Spearman’s correlation coefficient to verify the correlation between 2-Minute Step Test and measures of pain and physical activity (Numerical Pain Scale, Roland-Morris Disability Questionnaire, Pain-Related Catastrophizing Thoughts Scale, Tampa Scale of Kinesiophobia, and Baecke Habitual Physical Activity Questionnaire).ResultsSample is composed of 37 individuals, most of them female, with overweight and low back pain > 60 months. 2-Minute Step Test showed excellent test-retest (ICC = 0.903) and inter-rater (ICC = 0.925) reliability. Sport domain of the Baecke showed a significant correlation with the 2-Minute Step Test (rho = 0.444).Conclusion2-Minute Step Test is a reliable measure to measure the functional capacity of patients with chronic low back pain considering different times and examiners, as well as being positively correlated with sports practice.