Reliability of detection of lumbar lateral shift

Background and Purpose: The poor reliability of lateral shift detection has been attributed to lack of rater training, biologic variation, and test reactivity. This study aimed to remove the potential confounding arising from biological variation and test reactivity and control the level of rater experience/training in making judgments of lateral shift. Subjects: One hundred forty-eight raters with 3 levels of clinical physical therapy experience and training in the McKenzie method participated. Method: The raters viewed photographic slides of 45 patients with low back pain. Slides were judged on a numerical scale for presence and direction of a shift. Intrarater reliability was evaluated using the intraclass correlation coefficient (ICC) and interrater reliability was evaluated using both the ICC and kappa statistic. Results: Reliability of shift judgments was only moderate for all groups (eg, ICC [2, 1] values ranged from 0.48 to 0.64). Conclusion: Lateral shift judgements have only moderate reliability, even when trained raters judge stable stimuli. We propose that the photo model employed can be used to explore the source of error in this process.