Reliability and validity of the function in sitting test among non-ambulatory individuals with spinal cord injury

Context: Trunk impairment among non-ambulatory individuals with spinal cord injury (SCI) reduces the ability to maintain a functional sitting position and perform activities of daily living. Measuring functional sitting balance is complex and difficult in a clinical setting. The function in sitting test (FIST) is a clinical measure that includes the assessment of all the components of sitting balance. The purpose of this study is to assess the reliability and validity of the 14-item FIST among non-ambulatory individuals with SCI. Participants: Twenty-six individuals with chronic SCI. Outcome measures: Participants were evaluated with the FIST, the modified Functional Reach Test (lateral and forward mFRT) and a posturography assessment (virtual time to contact - VTC). The FIST was re-assessed during a second study visit 12 weeks later. Test-retest reliability was evaluated using intraclass coefficient correlation (ICC), the minimal detectable change (MDC) was calculated and the internal consistency reliability was assessed using Cronbach's coefficient-α. Concurrent validity of the FIST was also tested with the mFRT and the VTC. Results: Test-retest reliability was found to be excellent (ICC = 0.95) with a MDC of 4. The internal consistency was satisfactory (0.81). Moreover, the FIST correlates with the lateral mFRT (r = 0.64, P = 0.001) but not with the forward mFRT and the VTC. Conclusion: These observations provide evidence that the FIST is a reliable clinical measure with partially established validity for non-ambulatory individuals with SCI. Further studies are needed to strengthen the validity of the FIST and explore this measure in a larger sample.