Validating an Activity Monitor for Acute Care Patients: The Patient/Resident Mobility Tracker (PREEMPT).
Ann Tuzson, Christopher M Moore, Merrick Furman and 4 others
An ankle-worn activity monitor matched video-based truth data for hospital patients' sedentary and activity time, and for healthy adults' step count, stride length, and stepping time, all within pre-set equivalence margins.
Key findings
1All five mobility metrics (stride length, step count, stepping time, activity time, sedentary time) fell within the pre-set equivalence margins compared to video truth data, with the null hypothesis of non-equivalence rejected in every case.
2Hospitalized patients rated the device 9.38 out of 10 on a usability questionnaire (64.26 out of 70 on the raw scale), indicating strong approval.
3Data were successfully collected in 46 of 52 hospitalized patients; the six excluded cases were due to a camera setup error in the room, not a device failure.
Still to come
How it was doneWhat they foundWhat it means for PTs
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What it does not show
All participants had to understand the study and consent, which excluded most critically ill or cognitively impaired patients — the group most at risk from immobility. The authors acknowledge the sample was skewed toward more functional, cognitively intact patients. Stride length, step count, and stepping time were validated only in healthy adults performing scripted activities, not in the hospital setting. In hospitalized patients, only activity time and sedentary time were validated. The device's claimed ability to distinguish walking from wheelchair transport or peddling was not tested in actual hospitalized patients during this study; no patients in the cohort underwent those activities during the data-collection window. Single-site study at one academic medical center; no multicentre replication. Six of 52 hospitalized patients were excluded due to a camera setup error, reducing the analyzed sample.
Declared interests
Funded by the NIH National Institute of Nursing Research (Award R44NR015934). Five of the authors are salaried employees of Barron Associates, Inc., a for-profit company that is the grantee of that award and the owner of the intellectual property in the PREEMPT device. The company that owns the product employed the researchers and received the grant.
The easy way to misread this
Do not read this as validation of the device for all hospitalized patients. The study excluded anyone who could not consent (including most critically ill or cognitively impaired patients), stride length was validated only in healthy adults rather than in the hospital setting, and the device's ability to distinguish walking from wheelchair transport or peddling was never tested in actual patients during this study. The equivalence result tells you the sensor matches a video camera under these specific conditions; it does not tell you the device will work the same way for a sedated ICU patient or someone in a wheelchair.
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