Clinimetric testing of the Lumbar Spine Instability Questionnaire

Background: The Lumbar Spine Instability Questionnaire (LSIQ) is a self-report measure of 15 items. Previous studies have used the LSIQ as a measure of clinical instability; however, a comprehensive evaluation of its clinimetric properties has not been conducted. Objectives: The aim of this study was to evaluate the clinimetric properties of the LSIQ in patients with chronic nonspecific low back pain (LBP). Methods: In this clinical measurement study, the authors included patients with nonspecific LBP presenting to primary care clinicians in Australia. Rasch analysis was conducted to assess item hierarchy, targeting, unidimensionality, person fit, internal consistency, and differential item functioning. The researchers assessed test-retest reliability of total scores and individual item scores, as well as convergent and divergent validity. Results: A total of 107 participants with LBP (60 men and 47 women) were recruited. The results were variable. The LSIQ appeared to constitute a unidimensional measure, targeted the sample well, and showed adequate test-retest reliability. However, the scale had poor internal consistency, did not appear to function as an interval-level measure, and had unclear construct validity. Although no items appeared to be redundant, several items were biased by factors other than the proposed construct of the measure. Conclusion: The LSIQ does not seem to be ready to be implemented in clinical practice and may require theoretical reconsideration. Although the LSIQ provided satisfactory estimates for some clinimetric features, the authors do not consider the instrument to be useful as an interval-level measure but rather as an index. Future studies are needed to investigate whether the LSIQ could measure clinical instability or some other construct.