Abstract
BackgroundPhysical capacity tasks are useful tools to assess functioning in patients with low back pain (LBP), but evidence is scarce regarding the responsiveness (ability to detect change over time) and minimal important change (MIC). The aim was to investigate the responsiveness and MIC of 5-min walk, 1-min stair climbing, 50-ft walk, and timed up-and-go in patients with chronic LBP undergoing lumbar fusion surgery.MethodsIn this clinimetric study, 118 patients scheduled for lumbar fusion surgery for motion-elicited chronic LBP with degenerative changes were included. All patients performed the physical capacity tasks 5-min walk, 1-min stair climbing, 50-ft walk, and timed up-and-go 8–12 weeks before and six months after surgery. Responsiveness was evaluated by testing five a priori responsiveness hypotheses. The hypotheses concerned the area under the receiver operating characteristics (ROC) curve and correlations (Spearman’s rho) between the change scores of the physical capacity tasks, the Oswestry Disability Index 2.0 (ODI), and back pain intensity measured with visual analog scale (VAS). At least 80% of the hypotheses would have to be confirmed for adequate responsiveness. Absolute and relative MICs for improvement were determined by the optimal cut-off point of the ROC curve based on the classification of improved and unchanged patients according to construct-specific global perceived effect (GPE) scales.ResultsOne-minute stair climbing, 50-ft walk and timed up-and-go displayed adequate responsiveness (≥ 80% of hypotheses confirmed), while 5-min walk did not (40% of hypotheses confirmed). The absolute MICs for improvement were 45.5 m for 5-min walk, 20.0 steps for 1-min stair climbing, − 0.6 s for 50-ft walk, and − 1.3 s for timed up-and-go.ConclusionsThe results of responsiveness for 1-min stair climbing, 50-ft walk, and timed up-and-go implies that these have the ability to detect changes in physical capacity over time in patients with chronic LBP who have undergone lumbar fusion surgery.
Highlights
Physical capacity tasks are useful tools to assess functioning in patients with low back pain (LBP), but evidence is scarce regarding the responsiveness and minimal important change (MIC)
global perceived effect (GPE) Global perceived effect, Oswestry Disability Index 2.0 (ODI) Oswestry Disability Index, receiver operating characteristics (ROC) Receiver operating characteristic, visual analog scale (VAS) Visual analog scale aImproved patients were considered to be those who had scored the response alternatives “much better” or “better” on the construct-specific GPE scales and unchanged patients were those who had scored response alternatives “somewhat better,” “unchanged,” or “somewhat worse” bFor timed up-and-go, Hypotheses 1 and 2 were tested separately for the construct-specific GPE scales on walking and chair rise, respectively, since the task includes both of these activities cThe expected direction depends on whether a negative or positive change score of a physical capacity task indicates an improvement or deterioration
Responsiveness Hypothesis 1 was confirmed for 1-min walk, 50-ft walk, and timed up-and-go as the areas under the ROC curves generated with the construct-specific GPE scales were ≥ 0.70 for these tasks (Table 4)
Summary
Physical capacity tasks are useful tools to assess functioning in patients with low back pain (LBP), but evidence is scarce regarding the responsiveness (ability to detect change over time) and minimal important change (MIC). The aim was to investigate the responsiveness and MIC of 5-min walk, 1-min stair climbing, 50-ft walk, and timed up-and-go in patients with chronic LBP undergoing lumbar fusion surgery. The outcome of lumbar fusion surgery is often assessed with back-specific patient-reported outcome measures (PROMs) of disability, e.g. the Oswestry Disability Index (ODI). Patients rate their perceived limitations in performing various activities commonly affected by low back pain (LBP), such as walking, sitting and lifting [7, 8]. Previous research and clinical experience indicate discrepancies between patients’ scores on PROMs and how they perform activities when observed by others or as measured by wearable equipment (e.g. accelerometers) [13, 14]
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