Accuracy of wrist-worn activity trackers for measuring steps in patients after major abdominal surgery: A validation study.

Abstract

Wearable activity trackers provide a simple and objective measurement of postoperative mobilization. However, few have validated the accuracy of trackers in patients after major abdominal surgery. To examine the accuracy of wrist-worn activity trackers to measure steps of patients in early mobilization after major abdominal surgery, and to explore the influence of clinical variables and gait parameters on the accuracy of trackers. Forty-five patients after major abdominal surgery were recruited to participate in modified six-minute walk tests wearing three trackers simultaneously, the Fitbit Inspire HR, Xiaomi MI 4, and HONOR 5. The differences in displayed steps before and after the walking test were considered as the step counts measured by the trackers; the actual steps taken were determined as the average of the values manually counted by two researchers. The intraclass correlation coefficient, Bland-Altman method, mean percentage error, and mean absolute percentage error were used to assess the accuracy of trackers with reference to manual step counts. The three trackers undercounted postoperative steps by -65.5% to -23.5%. Analysis showed low-to-good agreement between step counts recorded by trackers and actual steps (ICC = 0.35-0.75); the mean absolute percentage errors ranged from 24.5% to 65.7%. For all trackers, mean absolute percentage errors correlated negatively with postoperative days (r = -0.626 to -0.744), walking speed (r = -0.714 to -0.854), step length (r = -0.466 to -0.615), and cadence (r = -0.681 to -0.790), while there were positive correlations between mean absolute percentage errors and the number of abdominal drains (r = 0.450-0.514). The specific activity trackers used in this study might not be reliable tools for measuring steps counts during the walking test in the early postoperative period for patients undergoing major abdominal surgery.