Accuracy of Wrist-Worn Activity Trackers for Measuring Steps in Patients after Major Abdominal Surgery

Abstract

Abstract Background Early mobilization is one of the key elements for successful enhanced recovery after surgery. Wearable activity trackers offer a simple means for objective measurement of postoperative mobilization. However, few studies have validated the accuracy of trackers after major abdominal surgery. We aimed to examine the accuracy of wrist-worn activity trackers in measuring steps of patients during early mobilization after major abdominal surgery; we also explored the influence of clinical variables and gait parameters on the accuracy of the trackers. Methods This cross-sectional study was carried out among 45 patients, who were instructed to participate in six-minute walk tests while 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 Mann-Whitney U, Kruskal-Wallis H, and Spearman’s rank correlation tests were used to assess the influence of demographic, clinical, and gait parameters related to step count accuracy. Results 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 (intraclass correlation coefficient = 0.35–0.75); the mean absolute percentage errors ranged from 24.5–65.7%. All trackers demonstrated greater error in detecting steps in patients who walked at slower speeds, with shorter strides, had more drains, and participated in the walking tests on earlier postoperative days. Conclusions This study offers detailed and novel understanding on the step count underestimation of trackers in the postoperative patient population. Our preliminary results suggest that step count data obtained by trackers in the early postoperative period should be considered with caution.