How do patients improve their timed up and go test? Responsiveness to rehabilitation of the TUG test in elderly neurological patients

Background: The timed up and go (TUG) test is widely used for assessing treatments effectiveness on elderly mobility. Although the TUG test consists of different tasks (e.g. walking and turning), the total TUG duration (TTD) is usually the only outcome measure, with TTD shortening indicating the patient's improvement. Research question: Does TTD shortening reflect the improvement of each TUG tasks or does it reflect the improvement of only some of them? Methods: This retrospective study recruited 120 elderly patients (mean, SD: 76.9, 6.6 years) admitted to inpatient rehabilitation because of an acute or chronic neurological disease (acute patients, AP; chronic patients, CP). TTD and TUG tasks duration was measured on admission and discharge (five trials/session) by means of the instrumental TUG test (ITUG). Likelihood ratios (LRs) were used for inferring TUG tasks improvement from TTD improvement. TTD and TUG tasks have improved if at least four measurements on discharge were shorter than the shortest measurement on admission. Results: TTD improvement per se is not enough to claim that all the TUG tasks have improved (LR +AP = 1.32; LR +CP = 1.85). Conversely, if TTD has not improved, not even a single TUG task has improved (LR −AP = 0.13; LR −CP = 0.19). If TTD has improved, there is at least one TUG task that actually improved (LR +AP = 3.17; LR +CP = 9.54). The improvement of all TUG tasks can be only inferred in the (unusual) event of a large TTD shortening (AP: >39%, LR +AP = 6.26; CP: >30%, LR +CP = 9.0). Significance: In most cases, TTD improvement is not associated with the improvement of all TUG tasks. Moreover, when TTD has improved there is at least a TUG task that has improved, but that remains unknown. To actually understand how treatments ameliorate patients’ mobility, ITUG with TUG task duration measurement should be preferred to TTD.