The Psychometric Properties of the Dubousset Functional Test in Patients With Lumbar Spinal Stenosis

Background

Lumbar spinal stenosis (LSS) may deteriorate the spinal structure and mobility, leading to various problems, including pain, fatigue, decreased physical function, gait and balance issues, and diminished quality of life. The Dubousset Functional Test (DFT) comprehensively evaluates the functional capacity of the spinopelvic muscle groups, gait, balance, and dual-tasking performance. This study evaluates the reliability and validity of the DFT in patients with LSS.

Methods

The DFT was performed twice per day at 1-h intervals in 30 patients with LSS. Before and after the tests, the patient′s pain was assessed using the Visual Analog Scale. The intraclass correlation coefficient (ICC [2,1]), Bland–Altman analysis, standard error of measurement (SEM95), and smallest detectable change (SDC95) were calculated at a 95% confidence level to determine interrater reliability. Concurrent validity was examined using the five-repetition sit-to-stand test (5R-STS) and the Oswestry Disability Index (ODI).

Results

The mean age of the patients was 55.0 ± 9.4 years, and the DFT score was 47.6 ± 3.3 s. The DFT has an acceptable reliability point estimate (ICC: 0.65–0.87). The DFT total score showed moderate correlations with the 5R-STS (r = 0.50) and ODI (r = 0.46), providing limited evidence of concurrent validity for lower-extremity functional performance and self-reported disability. The SEM95 was 2.46, and the SDC95 was 6.84. No increased pain or side effects were observed due to the DFT.

Conclusion

The DFT demonstrated acceptable reliability under the repeated-trial conditions used in this study, although the precision of the total-score reliability estimate was limited. The DFT showed preliminary concurrent validity in relation to sit-to-stand performance and self-reported disability in patients with LSS.