Repeatability of a treadmill gait stress test to understand the serum biomarker COMP in young healthy adults

Introduction: Cartilage damage in the human body represents a relevant problem due to the lack of regenerative capacity (Bi, 2018; Schünke et al., 2012, S. 79). Currently, there is no diagnostic procedure to determine the underlying processes (Nguyen et al., 2017). According to the current state of research, analyses using articular cartilage blood biomarkers are potential diagnostic methods for the early detection of cartilage damage (Bauer et al., 2006; Nguyen et al., 2017). The aim of this study is to determine the repeatability of load-induced changes in the concentration of the serum marker cartilage oligomeric matrix protein (sCOMP).
Methods: Young healthy volunteers (n = 10) were measured for the repeatability of sCOMP concentrations and kinetics on two identical measurement days within seven days. sCOMP concentrations were collected immediately before, immediately after and 30 minutes after a walking stress test. Additional spatiotemporal parameters and ground reaction force were measured with an instrumented treadmill. 24 hours before each measurement day, activity data were recorded with an accelerometer. Differences between measurement days were calculated by applying the paired sample t-test. Repeatability between measurement days was determined using intraclass correlation coefficients (ICC).
Results: No significant differences of all sCOMP absolute concentrations could be detected between measurement day A and B, which is confirmed by moderate to good agreements (ICC
≥ 0.695). The spatiotemporal parameters as well as the ground reaction force parameters showed no difference and additionally good agreement (ICC ≥ 0.847). Finally, the activity data showed no difference between the two measurement days as well as weak to good agreements (ICC ≤ 0.808).
Conclusion: The agreements and the non-significant differences between both measurement days of the absolute sCOMP concentrations show reproducible load-induced concentration changes. In addition, repeatability was confirmed while walking at normal speed on an instrumented treadmill. In conclusion, the standardization protocol has proven suitable for testing repeatability with a framework that is as identical as possible, which could be helpful for further research.