Comparability of Output from Actigraph Accelerometer Models 7164 and GT3X+ in Youth with Multiple Sclerosis
Objectives: To determine the level of consistency between minutes spent in sedentary, light, moderate, vigorous, moderate-vigorous (MVPA) activity using ActiGraph 7164 and GT3X+ accelerometers in youth with MS.
Methods: Youth with a diagnosis of MS were recruited at The Hospital for Sick Children in Toronto, Canada. Youth wore the 7164 and GT3X+ accelerometers simultaneously for 7 days. Time spent in sedentary, light, moderate, vigorous, MVPA activity was calculated. Consistency between time spent at different intensities were analyzed by intra-class correlation coefficients (ICC) with 95% confidence intervals (CI). Mean differences and limits of agreement were also calculated and visualized using Bland-Altman plots. Ethics approval was obtained.
Results: 17 youth (16.65(3.03)y.o., F=12) were included in the analysis. The average number of valid days was 5.56±1.58. The agreement and consistency between the two devices were: sedentary (mean difference=2.31 min/day, ICC=0.91, 95% CI 0.76-0.96), light (mean difference=-3.06 min/day, ICC=0.91, 95% CI 0.78-0.96), moderate (mean difference=5.46 min/day, ICC=0.93, 95% CI 0.83-0.97) and MVPA (mean difference=5.16/day, ICC=0.92, 95% CI 0.82-0.97) intensity. Poor consistency (mean difference=-0.32 min/day, ICC=0.45, 95% CI 0.01-0.75) was found between the devices for activities that were vigorous in nature. The removal of an outlier improved the consistency between the devices for vigorous intensity (mean difference=-0.02 min/day, ICC=0.90, 95% CI 0.76-0.96) and remained unchanged across the other intensities (ICC range=0.90-0.93).
Conclusions: Results suggest sufficient consistency between ActiGraph 7164 and GT3X+ for time spent in sedentary, light and vigorous intensity levels in youth with MS. Despite comparable output, large mean differences and wide limits of agreement for minutes of moderate and MVPA indicate poor agreement between the two devices. Further work will investigate if this is ameliorated with a correction factor.