Evaluation of the 6-minute walking test as a smartphone app-based self-measurement of objective functional impairment in patients with lumbar degenerative disc disease

Abstract

OBJECTIVEDigital transformation enables new possibilities to assess objective functional impairment (OFI) in patients with lumbar degenerative disc disease (DDD). This study examines the psychometric properties of an app-based 6-minute walking test (6WT) and determines OFI in patients with lumbar DDD.METHODSThe maximum 6-minute walking distance (6WD) was determined in patients with lumbar DDD. The results were expressed as raw 6WDs (in meters), as well as in standardized z-scores referenced to age- and sex-specific values of spine-healthy volunteers. The 6WT results were assessed for reliability and content validity using established disease-specific patient-reported outcome measures.RESULTSSeventy consecutive patients and 330 volunteers were enrolled. The mean 6WD was 370 m (SD 137 m) in patients with lumbar DDD. Significant correlations between 6WD and the Core Outcome Measures Index for the back (r = −0.31), Zurich Claudication Questionnaire (ZCQ) symptom severity (r = −0.32), ZCQ physical function (r = −0.33), visual analog scale (VAS) for back pain (r = −0.42), and VAS for leg pain (r = −0.32) were observed (all p < 0.05). The 6WT revealed good test-retest reliability (intraclass correlation coefficient 0.82), and the standard error of measurement was 58.3 m. A 4-tier severity stratification classified patients with z-scores > −1 (no OFI), −1 to −1.9 (mild OFI), −2 to −2.9 (moderate OFI), and ≤ −3 (severe OFI).CONCLUSIONSThe smartphone app-based self-measurement of the 6WT is a convenient, reliable, and valid way to determine OFI in patients with lumbar DDD. The 6WT app facilitates the digital evaluation and monitoring of patients with lumbar DDD.

Examining the Association Between Self-Reported Estimates of Function and Objective Measures of Gait and Physical Capacity in Lumbar Stenosis

“…This is interesting because objective markers and PROs have not always correlated, and PROs alone may be necessary but insufficient for complete functional assessments. 7 , 8 , 13 , 29 , 30 , 31 , 32 Although measures like ODI and SF-36 may have overlapping information, the literature suggests that they provide unique and complementary data in the assessment of pain and spine outcomes. Adding objective indicators such as IMU gait features and physical capacity measures to subjective ratings could enhance evaluation of clinical outcomes in patients with LSS.…”

Distance to first symptoms measured by the 6-min walking test differentiates between treatment success and failure in patients with degenerative lumbar disorders

“…The 6-min walking test (6WT) is increasingly applied as an objective outcome measure in patients with lumbar DLD [5]. We recently developed a smartphone app-based version of the 6WT, which demonstrated excellent reliability [6,7]. The 6WT can be self-performed by the patient in his/her home environment, and results are standardized with respect to age and sex [6,8,9].…”

“…We recently developed a smartphone app-based version of the 6WT, which demonstrated excellent reliability [6,7]. The 6WT can be self-performed by the patient in his/her home environment, and results are standardized with respect to age and sex [6,8,9]. By providing the ability to monitor patients from afar, digital outcome measures are invaluable tools for physicians and patients.…”

“…This is a trend that will only accelerate in a time when a global pandemic hampers avoidable physical "face-toface" consultations as those might endanger elderly or particularly fragile patients [11,12]. The 6WT's primary outcome measure is the maximum distance a patient can walk within 6 min (6WD = 6-min walking distance, measured in metres) [6]. In addition, the 6WT-app provides patients with the possibility to push a "flash button" and records both the time (TTFS = time to first symptoms, measured in seconds) and distance (DTFS = distance to first symptoms, measured in metres) when first symptoms of neurogenic claudication appear.…”

“…While the 6WD expresses the result of walking restrictions that occur over the whole duration of the test time, TTFS and DTFS may give more granular information about the severity or urgency of patient's symptoms. Studies have proven the 6WD to be a reliable, valid, and responsive measure of functional impairment [6]. The added value of both TTFS and DTFS in addition to the 6WD, however, is yet unclear.…”