Comparing Step Count Accuracy in ActiGraph GT3X+ and StepWatch3 Activity Monitors in Geriatric In-Patients

Purpose/Objectives & Rationale: To compare step count accuracy of ActiGraph GT3X+ monitors (hip and ankle placement) with the StepWatch 3 in geriatric in-patients.

Relevance: The StepWatch 3 activity monitor is the gold standard for detecting steps in individuals who walk very slowly. However, because the ActiGraph GT3X+ monitor is capable of collecting additional activity intensity data, it may be a more functional monitor to use.

Materials and Methods: Geriatric in-patients (n=38, 34 females, 83.2 ± 7.1 years of age) wore a StepWatch3 on the right ankle and two ActiGraph GT3X+ monitors (left ankle and right hip) while completing a self-paced walk. Observed steps were counted with a hand tally counter. The walking distance varied with patient tolerance (range 83-404 observed steps). Monitor detected steps were compared to observed steps.

Analysis: Kruskal-Wallis ANOVA on ranks was used to compare absolute percent error among the monitors (Tukey’s multiple comparison for post-hoc analyses).

Results: Mean gait speed for the participants was 0.42 ± 0.15 m/s. There were no significant differences in accuracy for the StepWatch3 and the ActiGraph GT3X+ worn at the ankle (median absolute percent error values 2.3 versus 2.5 respectively, p=0.54). Step count absolute error values were significantly higher when the GT3X+ was worn at the hip (median 18.9, p<0.05).

Conclusions: When the ActiGraph GT3X+ is worn at the ankle and analyzed with the low frequency extension algorithm similar step count accuracy is achieved compared to the criterion StepWatch3 in older adults who walk very slowly. Researchers and clinicians who have access to GT3X+ monitors can feel confidant using them in this population.