Quantitative Evaluation of Gait Disturbance on an Instrumented Timed Up-and-go Test

Although the 3-m timed up-and-go test (TUG) is reliable for evaluating mobility, TUG time is insufficient to evaluate mild gait disturbance; we, therefore aimed to investigate other measurements with instrumented TUG (iTUG) using a free smartphone application. Our inclusion criterion in this study is only that participants can walk without any assistance. This study included three heterogeneous groups; patients who underwent a tap test or shunt surgery, 29 inpatients hospitalized for other reasons, and 87 day-care users. After the tap test, 28 were diagnosed with tap-positive idiopathic normal-pressure hydrocephalus (iNPH) and 8 were diagnosed with tap-negative. Additionally, 18 patients were assessed iTUG before and after shunt surgery. During iTUG, time and 3-dimensional (3D) acceleration were automatically recorded every 0.01 s. A volume of the 95% confidence ellipsoid (95%CE) of all plots for 3D acceleration was calculated. Additionally, an iTUG score was defined as (95%CE volume) 0.8 / 1.9 - 1.9 × (time) + 60. The measurement reliability was evaluated using intraclass correlations and Bland-Altman plots. The participants with mild gait disturbance who accomplished within 13.5 s on the iTUG time had the 95%CE volumes for 3D acceleration of ≥70 m3/s6 and iTUG scores of ≥50. The mean iTUG time was shortened and the mean 95%CE volumes and iTUG scores were increased after the tap test among 28 patients with tap-positive iNPH and after shunt surgery among 18 patients with definite iNPH. Conversely, the mean iTUG score among 8 patients with tap-negative was decreased after the tap test. The intraclass correlations for the time, 95%CE volume and iTUG score were 0.97, 0.80 and 0.90, respectively. Not only the iTUG time but also the 95%CE volume was important for evaluating mobility. Therefore, the novel iTUG score consisting both is useful for the quantitative assessment of mobility.