How reproducible is home-based 24-hour ambulatory monitoring of motor activity in patients with multiple sclerosis?

Objective To determine the reproducibility of 24-hour monitoring of motor activity in patients with multiple sclerosis (MS). Design Test-retest design; 6 research assistants visited the participants twice within 1 week in the home situation. Setting General community. Participants A convenience sample of ambulatory patients (N=43; mean age ± SD, 48.7±7.0y; 30 women; median Expanded Disability Status Scale scores, 3.5; interquartile range, 2.5) were recruited from the outpatient clinic of a university medical center. Interventions Not applicable. Main Outcome Measures Dynamic activity and static activity parameters were recorded by using a portable data logger and classified continuously for 24 hours. Reproducibility was determined by calculating intraclass correlation coefficients (ICCs) for test-retest reliability and by applying the Bland-Altman method for agreement between the 2 measurements. The smallest detectable change (SDC) was calculated based on the standard error of measurement. Results Test-retest reliability expressed by the ICC