Reliability of a smartphone app to objectively monitor performance outcomes in degenerative cervical myelopathy: an observational study

Objectives: To assess the reliability of the MoveMed battery of performance outcome measures. Design: Prospective observational study. Setting: Decentralised secondary care in England, United Kingdom. Participants: Seven adults aged 59.5 (SD 12.4) who live with degenerative cervical myelopathy (DCM) and possess an approved smartphone. Primary and secondary outcome measures: The primary outcome was to determine the test-retest reliability of the MoveMed performance outcomes using the intra-class correlation of agreement (ICCagreement). The secondary outcome was to determine the measurement error of the MoveMed performance outcomes using both the standard error of agreement of the mean (SEMagreement) and the smallest detectable change of agreement (SDCagreement). Criteria from the Consensus-based Standards for the selection of health Measurement Instruments (COSMIN) manual were used to determine adequate reliability (i.e., ICCagreement ≥ 0.7) and risk of bias. Disease stability was controlled for using two minimum clinically important difference (MCID) thresholds obtained from the literature on the patient-derived modified Japanese Orthopaedic Association (P-mJOA): namely, MCID ≤1 point and MCID ≤2 points. Results: All tests demonstrated moderate-to-excellent test-retest coefficients and low measurement errors. In the MCID ≤1 group, ICCagreement values ranged from: 0.84–0.94 in the Fast Tap Test, 0.89–0.95 in the Hold Test, 0.95 in the Typing Test, and 0.98 in the Stand and Walk Test. SEMagreement values ranged from ±1 tap, ±1–3% stability score points, ±0.06 keys per second, and ±10 steps per minute, respectively. SDCagreement values were ±3 taps, ±4–7% stability score points, ±0.2 keys per second, and ±27 steps per minute. In the MCID ≤2 group, ICCagreement values ranged from: 0.61–0.91, 0.75–0.77, 0.98, and 0.62, respectively; SEMagreement values from: ±1 tap, ±2–4% stability score points, ±0.06 keys per second, and ±10 steps per minute; and SDCagreement values from: ±3–7 taps, ±7–10% stability score points, ±0.2 keys per second, and ±27 steps per minute. Furthermore, the Fast Tap, Hold, and Typing Tests obtained sufficient ratings (ICCagreement ≥ 0.7) in both MCID≤1 and MCID≤2 groups. No risk of bias factors from the COSMIN Risk of Bias checklist were recorded. Overall, 'very good' quality evidence of sufficient reliability was found for the MoveMed battery in DCM. Conclusions: Criteria from COSMIN provide 'very good' quality evidence of the reliability of the MoveMed tests in an adult population living with DCM. ### Competing Interest Statement All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare: support from MoveMed Ltd for the submitted work; BMD is Chief Executive Officer of MoveMed Ltd; AYT is Chief Scientific Officer of MoveMed Ltd; IL has received consultation fees from DePuy Synthes, royalties from Globus and acted as an advisor to Chiefy Inc; MRNK is Chief Medical Officer of MoveMed Ltd; no other relationships or activities that could appear to have influenced the submitted work. ### Funding Statement This study was funded by MoveMed Ltd. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethics committee of University of Cambridge gave ethical approval for this work (HBREC.2022.13). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present work are contained in the manuscript.