Validity and Reliability of an Objective Measurement of Functional Impairment in Lumbar Degenerative Spine Disease: The Timed-Up-and-Go (TUG) Test

Background: The indication for surgical treatment of lumbar degenerative spine disease is generally based on patient-related factors such as pain, functional disability, and reduced health-related quality of life (hrQoL) in view of corresponding radiological imaging findings. In addition to subjective scores, objective measures of functional disability may be helpful in the process of clinical decision making. Methods: In a prospective two-center study, functional disability was determined in 253 patients scheduled for lumbar spine surgery and a representative cohort of n = 111 healthy subjects as the control group by a simple objective test, the timed-up-and-go (TUG) test. The TUG test outcome parameter (time in seconds) was correlated to validated subjective measures of pain (visual analogue scale [VAS]), functional disability scores (Oswestry, Roland–Morris, etc.), and hrQoL (Short Form-12, Euro Quol, etc.). Results: The TUG test showed excellent intrarater (intraclass correlation coefficient [ICC] 0.97) and interrater reliability (ICC 0.99) with a standard error of measurement of 0.21 and 0.23 seconds, respectively. The validity of the TUG test is demonstrated by appropriate relationships with the VAS back (Pearson correlation coefficient [PCC] 0.25) and VAS leg pain (PCC 0.29), functional impairment (Roland–Morris Disability Index [PCC 0.38] and Oswestry Disability Index [PCC 0.34]) as well as with health-related quality of life (SF-12 MCS [PCC −0.25]; SF-12 PCS [PCC −0.32]; and Euro-Qol [PCC-0.28]). The upper limit of normal was determined to be 11.52 seconds. Mild (<33th percentile), moderate (33th to 66th percentile), and severe disability (>66th percentile) as determined by the TUG test were determined as <13.4 seconds, 13.4–18.4 seconds, and >18.4 seconds, respectively. Conclusions: The TUG test is a quick, easy-to-use, valid, and reliable tool to objectively evaluate the functional impairment in patients with degenerative spine disease. Patients in the clinical setting with a TUG test time greater than 12 seconds can be considered to have functional impairment.