Assessment of the Minimum Clinically Important Difference in the Timed Up and Go Test After Surgery for Lumbar Degenerative Disc Disease

BACKGROUND: The Timed Up and Go Test (TUG Test) has previously been described as a reliable tool to evaluate objective functional impairment in patients with degenerative disc disease. OBJECTIVE: The aim of this study was to assess the minimum clinically important difference (MCID) of the TUG Test. METHODS: The TUG Test (measured in seconds) was correlated with validated patient-reported outcome measures (PROs) of pain intensity (Visual Analog Scale for back and leg pain), functional impairment (Oswestry Disability Index, Roland Morris Disability Index), and health-related quality of life measures (Short Form-12 and EuroQol 5D). Three established methods were used to establish anchor-based MCID values using responders of the following PROs (Visual Analog Scale back and leg pain, Oswestry Disability Index, Roland Morris Disability Index, EuroQol 5D index, and Short Form-12 Physical Component Summary) as anchors: (1) average change, (2) minimum detectable change, and (3) change difference approach. RESULTS: One hundred patients with a mean +/- SD age of 56.2 +/- 16.1 years, 57 (57%) male, 45 patients undergoing microdiscectomy, 35 undergoing lumbar decompression, and 20 undergoing fusion surgery were studied. The 3 MCID computation methods revealed a range of MCID values according to the PRO used from 0.9 s (Oswestry Disability Index based on the change difference approach) to 6.0 s (EuroQol 5D index based on the minimum detectable change approach), with a mean MCID of 3.4 s for all measured PROs. CONCLUSION: The MCID for the TUG Test time is highly variable depending on the computation technique used. The average TUG Test MCID was 3.4 s using all 3 methods and all anchors.