OP0108 FITBIT VALIDITY AS AN ACTIVITY MONITOR IN IDIOPATHIC INFLAMMATORY MYOPATHY
Authors: R. Aggarwal, A. Sharma, R. Lomanto Silva, S. Keret, S. Moghadam-Kia, C. V. Oddis
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Idiopathic inflammatory myopathies (IIM, myositis) are a systemic autoimmune disease leading to debilitating muscle weakness and significant limitations in daily activities. Physical activity monitors (PAM) are validated and recognized measures of the frequency and intensity of physical activities. Given the unmet need for objective, continuous, longitudinal outcome measures of physical activity and function in myositis, we assessed compliance, reliability, and validity of widely used commercial PAM – Fitbit© in evaluating physical activity in myositis patients. <h3>Objectives:</h3> To investigate the psychometric properties and performance of Fitbit as a wearable activity tracker in an IIM cohort. <h3>Methods:</h3> "Myositis Patient Centered Tele-Research (MyPACER)" is a multi-center observational prospective study conducted over 6 months on IIM patients with dermatomyositis (DM), necrotizing myopathy (NM) and polymyositis (PM, including anti-synthetase syndrome). The study had two cohorts, 1. Tele-Research Cohort (TRC): remotely enrolled from any location in the United States, and 2. Center-Based Cohort (CBC): a traditional cohort with enrollment from 2 myositis centers. Functional and Patient-Reported Assessments were completed monthly, including a health assessment questionnaire, patient global disease activity, PROMIS-physical function 20, and functional tests Timed-Up-and-Go (TUG) and Sit-To-Stand (STS)). Participants were asked to use their wrist-based Fitbit for (≥10 hours/day) for 7 consecutive 7 days once a month. Average daily steps per minute (Ave step/min) &amp; average daily peak cadence (Ave peak cadence) were evaluated as PAM measures. <h3>Results:</h3> A total of 120 IIM patients (mean age 55.5±13.43; 75% females; 80.8% White) were enrolled in the study, comprising 82 in the Main TRC group and 38 in the CBC group (Table 1). There were 51.7% DM, 39.2% PM, and 9.1% NM. The TRC and CBC cohorts were similar in demographics and disease subtypes. Age was significantly correlated with the(p=0.01) but not with Ave peak cadence, showing decreased steps with advancing age. Gender, race/ethnicity, or disease subtypes were not associated with PAM measures. On data analysis, 90% of patients completed at least one valid day on their Fitbit devices. The compliance with Fitbit was very high, with participants wearing devices on most days of the week (average = 6.52 days) for the most visits (average 5.73 visits), with similar results for remote or local recruitment. Ave steps/min and Ave peak cadence showed strong test-retest reliability (r=0.89 and r=0.86, p&lt; 0.0001 &amp; p= 0.0001) and were strongly correlated within the patient. On longitudinal analysis, the two groups using a mixed model between the baseline and 6th-month visits had no significant differences in the average steps per minute (p=0.09). However, a difference was noted in the peak cadence (p=0.02). The CBC group had a mean increase of 0.37/visit compared to the TRC group -.04/visit. <h3>Conclusion:</h3> In a large IIM cohort, Fitbit PAM variables demonstrate favorable compliance and psychometric properties with strong test-retest reliability and a significant difference between baseline and 6th-month visits on average. peak cadence. <h3>REFERENCES:</h3> <b>NIL.</b> <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> <b>None declared.</b>