Validity, Reliability, and Feasibility of Smartphone Application Intended for Home Measurement of Gait Speed and Other Gait Dynamics in Older Adults with Blood Cancers
Authors: Lee Pei-An , Dumontier Clark , Yu Wanting , Ho Kristi T , Groblewski Nicholas , Zhou JunHong , Travison Thomas , Testa Marcia , Hshieh Tammy , Kim Dae , Driver Jane A , Lo On-Yee , Manor Brad , Abel Gregory A 
Published: December 2023

Introduction: Gait speed is a cardinal measure of mobility and frailty recommended to be assessed in all older adults with cancer (Dale, JCO, 2023). Four-meter gait speed (4MGS) is strongly predictive of mortality and hospitalization in older adults with hematologic malignancies (Liu, Blood, 2019). Remote monitoring technology can expand measurement of gait speed beyond the clinic (Clancy, JCO CCI, 2023), and smartphone applications (App) have been developed and validated to measure meaningful gait metrics via embedded internal motion sensors (Manor, JMIR Mhealth Uhealth, 2018). However, the validity and reliability of a smartphone App for remotely measuring gait speed in older adults is not known, nor is the feasibility of using an App to measure longitudinal gait speed in older adults with blood cancers.
Methods: We conducted two studies to (1) determine the validity and reliability of a smartphone App in measuring 4MGS in community-dwelling older adults, and (2) determine the feasibility of measuring 4MGS weekly for six weeks in older adults with multiple myeloma (MM) and myelodysplastic syndromes (MDS).
For the validity and reliability study, we enrolled adults aged ≥ 65 years living in an independent living housing facility. Each participant self-administered two supervised and three unsupervised gait assessments at home via the smartphone carried in their pocket, with the App providing multimedia instructions on how to complete the test. For each gait assessment, the participants walked back and forth along a 4-meter strip of ribbon for 45 seconds. For the first two supervised sessions, while the participants were self-administering the gait assessment, the study team concurrently captured their walking performance with a video camera (as a gold standard). For the following three unsupervised sessions, the participants administered the gait assessment App alone. We obtained the time for the first instance of walking along the 4-meter ribbon before turning and compared the gait speed (i.e. dividing 4 meters by the time) between the smartphone and the video capture.
For the feasibility study, we enrolled patients age ≥73 years with either MDS or MM cared for at Dana-Farber Cancer Institute. Patients self-administered the gait assessment described above alone at home once a day for six weeks after a dedicated teaching session with study staff. We reported completion rates and participants' feedback regarding acceptability.
Results: 14 older adults (77.2±6.3, 13 females) completed the validity and reliability study. The smartphone 4MGS demonstrated strong criterion validity yielding a high correlation with the camera 4MGS ( Figure 1) along with high reliability as demonstrated by high internal consistency and low measurement error ( Figure 2). The smartphone 4MGS also showed good test-retest reliability over three unsupervised sessions (intra-class correlation coefficient 0.78).
In the feasibility study, 12 patients (79.3±3.14, 4 females, 50% MDS, 42% MM, and 8% both) were enrolled out of 19 contacted for recruitment (63%). To date, nine have completed the study: 9/9 completed at least one 4MGS test, 8/9 (89%) completed at least three weeks, and 3/9 (33%) completed all six weeks. When asked, “How important is measuring your function and mobility to you?” on a scale of 1 (low) to 5 (high), 7/9 participants answered 4 or 5. When asked to rate their experience completing the walking tests on a scale of 1 (very poor) to 5 (very good), 6/9 participants answered 4 or 5. When asked the degree to which one agrees with the statement, “I feel that the walking tests are too burdensome,” on scale of 1 (strongly disagree) to 5 (strongly agree), 9/9 patients answered 1 or 2.
Conclusions: The App was both valid and reliable in measuring 4MGS in older adults' homes. User acceptance was also high, and the app was rated as minimally burdensome by patients with blood cancers with the majority completing at least three weekly home 4MGS tests. Our findings support using existing smartphone technology to assess a key measure of mobility and frailty in the homes of older adults with blood cancers, allowing for more frequent longitudinal assessment of how blood cancers and their treatments impact older adult mobility and frailty.